|
RDSAP Manual March 2012
RDSAP Manual March 2012
Contents
Section 1 --- Introduction
Section 2 --- Energy rating and the EPC
Section 3 --- The RDSAP software
Section 4 --- Property features
Section 5 --- Constructions
Section 6 --- Space heating
Section 7 --- Water heating
Section 8 --- Renewables
Section 9 --- Recommendations
RDSAP Manual March 2012
Section one | Introduction
Welcome to this latest release of RDSAP
Training Manual. We hope that you find it easy to follow and
simple to use.
This version of the manual has been produced to coincide with
the introduction of the RDSAP 9.91 methodology in April 2012,
which brings some substantial changes over previous versions.
RDSAP Manual March 2012
How to use the Manual
This manual contains much of the technical information you will need
during your training and assessment for the Domestic Energy Assessor
(DEA) qualification. However, we may provide supplementary guidance as
required in the form of additional handouts.
Additional information may also be provided from time to time by other
means, such as by email. It is advisable to add any supplements to the
manual binder because once you are qualified it will be up to you to
maintain your knowledge of the latest conventions. The energy
assessment industry is a fast developing one and changes are inevitable
and regular.
It is strongly recommended that you read more widely than this manual
on some technical areas such as, for example, building construction.
While the basics are covered here, you may wish to continue to increase
your understanding of residential construction technology in order that
you feel competent to inspect the full range of residential property. A
current reading list supplied in Appendix 2 at the end of this manual.
Becoming qualified is not just a matter of learning the technical aspects of RDSAP.
There are other aspects to consider such as understanding the regulatory
framework within which DEAs operate.
This manual can be interactive, and in fact, we have deliberately made
space available for you to scribble away–so please feel free to make
whatever notes, reminders or diagrams you need to within the pages.
Just make sure that your notes are legible and technically correct as the
manual will be a useful point of reference, not just during training, but
also for information in the future. There are often times when it is useful
to confirm your instincts with a quick check in the manual.
The manual is divided into a number of clearly laid out Sections relating
to major subject areas, e.g. heating or construction. Within each Section
there are sub-sections containing subjects that are referred to in the
contents page, for ease of location.
RDSAP Manual March 2012
2.
History of
energy rating
Section two | Energy rating and the EPC
Energy rating of buildings is not new and it has long been known that as
much as 27% of our total CO2 emissions come from our homes.
SAP is used to produce energy ratings for new homes.
RDSAP
The Reduced Data SAP (RDSAP) is the government approved survey
system used to produce the Energy Performance Certificates (EPCs)
required by 2002 European Energy Performance of Buildings Directive
(EPBD), which came into force in 2006. The EPBD seeks to reduce the
amount of CO2 which is emitted as a result of heating, lighting and
providing hot water to UK homes, many of which have remained poorly
insulated.
With certain exceptions an Energy Performance Certificate (EPC) is
required whenever a residential property is sold or let and is currently
valid for 10 years. The EPC gives prospective buyers and tenants upfront information about the energy efficiency and running costs of the
property they are considering occupying. The rating system that the
EPC illustrates means that they can compare one property against
another before choosing and, it is hoped that landlords and vendors
would feel some pressure to upgrade their properties to make them
more marketable and thereby some progress could be made in reducing
the levels of CO2 emissions.
The physical RDSAP survey of a home required to produce an EPC is a
non-invasive inspection. The DEA is not required to lift carpets to see
the floors or to drill holes in the walls to see the insulation and is
therefore limited in what they can see of the property. There may be
some reliance on documentary evidence instead.
RDSAP produces an EPC that, on its front page, shows an eye-catching
and easy-to-read graphical illustration of the energy performance of the
property similar to the labels displayed on white goods.
RDSAP Manual March 2012
The EPC
 The page 1 of the EPC shows the energy
efficiency rating graph which illustrates the current rating (on
the graph above of 49 or band E) and the potential rating (above
of 75 or band C) that the property could achieve if the
recommendations contained in the report were implemented.
 The graph starts at 1 in the red bar and extends to 100 in the
dark green and represents the cost to the occupant of heating,
lighting and hot water for the property. A low number in the red
is an inefficient property and a high number in the green is an
extremely efficient one.
 It is possible for a property to score above 100 but this is
extremely rare and would normally involve exporting energy
gained from a renewable energy system. It means that the cost
of the energy consumption of the property is more than met by
the ‗income‘ obtained from exporting surplus energy.
 On the front page the EPC will also provide an indication of the
costs of providing heating, hot water and lighting to the property
over a three year period along with a clear indication of the
financial incentive to implementing the recommendations, i.e.
the savings that could be made.
It is important to note that these costs will not necessarily correlate
with the occupant‘s billing history because RDSAP uses ‗standard
occupancy‘ assumptions that may not reflect actual occupancy of the
property.
RDSAP Manual March 2012
Standard
occupancy
Standard occupancy is an important concept in energy rating because,
in order to provide a means by which readers of an EPC can compare
one property with another, a level playing field must first be achieved.
RDSAP Manual March 2012
For example, you might inspect a five-bedroom house occupied by a
single person whose running costs are lower than if the property were
occupied by a family of five people. Conversely, you might encounter a
large family inhabiting a very small flat and who use a lot of hot water
and considerable heat. The RDSAP rating ignores the occupants and
their behavioural patterns, focusing instead on the dwelling itself; its
fabric, heating, lighting, etc.
RDSAP works by measuring the annual cost of maintaining an
acceptable temperature regime in a dwelling. The assumption is that an
acceptable regime would be achieved by heating the property to 21
degrees Celsius in the lounge and 18 degrees Celsius in other habitable
rooms for 9 hours per week day and 16 hours at weekends.
The calculation uses the size of the property to estimate a suitable
average number of occupants and hence the hot water requirements for
that number of occupants.
This method is sometimes referred to as an ‗asset rating‘.
Recommendations The subject of recommendations is dealt with in more depth in Section
nine of this manual.
The EPC presents the reader with recommendations for improving the
fabric of the building, the heating, lighting and other areas. The top
three recommendations are shown on the first page of the report (see
below). There is also a first reference to the Green Deal in this section.
The improvements suggested help to prioritise the different ways of
saving energy, illustrated over a three year period.
RDSAP Manual March 2012
Some improvements make obvious economic sense, and others are
really only realistic considerations when a particular item requires
replacing. Loft insulation and hot water cylinder insulation, for example,
are obvious improvements, as they are cheap to purchase, can be easy
to install, and often save enough energy to produce real savings in less
than a year.
On the other hand, double-glazing and a replacement central heating
boiler are examples of improvements that cost far more, and this
means that they often will not be replaced unless there is the need, i.e.
a broken boiler or rotting/leaking window frames are present. The idea
is to present the homeowner with enough information to help them
decide on the best value for money when investing in energy efficiency.
The recommendations report offers an independent comparison of the
options–for example: installing new double-glazing (often only adding
2-4 SAP points) with a new boiler and controls (which could easily add
in excess of 10 SAP points).
The running costs associated with the ratings can also help the
consumer to identify the best ways to target their money to reduce fuel
bills.
Energy efficiency measures do make sense—for cost and comfort. A
typical 1960s house could have its fuel bills reduced by £200 per year
for an expenditure of about £500–an effective rate of return of 40%–
tax-free and inflation proof. Warmer, less draughty properties are
generally more comfortable to live in and may command higher prices
when sold or rented. Furthermore, our understanding of the ill effects of
carbon dioxide and other pollutants on our environment should be
reason enough to act.
RDSAP Manual March 2012
Other information
on the EPC
Page 2 of the EPC also contains basic details of the property‘s
construction, levels of insulation, heating system, hot water system,
lighting and other features and these are given an easily interpreted
star-rating, depending on how efficient they are deemed to be. It is
important that DEAs record these elements accurately during their
inspection.
Page 2 also shows details of any low and zero carbon technologies
present.
Page 3 (detail above) contains the full set of recommendations and an
indicative cost for each, together with suggested savings per year. The
green ticks suggest the measure could be applicable for Green Deal
funding and the orange tick suggests partial Green Deal funding.
Page 4 of the EPC (detail above) shows the environmental impact rating
graph which illustrates carbon emissions associated with the property,
expressed in tonnes of carbon dioxide produced per year.
RDSAP Manual March 2012
Page 5 of the EPC (detail above) shows the details of any Green Deal
charge associated with the property, including details of the installed
measures, in this case loft insulation and double glazing, their monthly
costs and savings, balance to repay and the interest rate charged.
Survey of the property
Data collection
Consider for a moment what it is that you are actually doing when
assessing the energy performance of a property. An input of heat is
needed to replace the heat lost through the envelope of the dwelling.
Some of this comes from natural solar input or is generated by the
occupants, but most of it has to be supplied by the heating systems. So
the DEA collects information on those characteristics of the dwelling
which influence the heat loss; as well as the characteristics of the
heating system.
While learning the process of inspection you can follow a
survey form which will prompt you with the data
items you need to record while at the property. Take care not to
miss anything at the property as doing so may mean you are forced
to return again later. When completing the survey forms, make your
entries clear and if you do not use a section strike a line through it to
show that you have not simply forgotten to complete it. For
example, if there are no extensions strike a line through the section
of the form that relates to extensions.
RDSAP Manual March 2012
Your site notes or survey forms are very important, firstly as a vital part
of the training and assessment process, but also (once you are
qualified) as part of the auditing process that DEAs are subject to by all
accreditation schemes.
You are obliged to maintain your site notes for a period of no less than
15 years. It is perfectly possible that you could be challenged on your
findings long after the EPC was completed and your notes must be good
enough to defend your position in this event.
You will collect information on the building, the age, construction and
insulation present in the dwelling, together with information about the
heating and hot water systems and any renewable energy systems.
Your survey forms should provide supporting evidence to back up any
decisions you make. For example, it is not good enough simply to state
that the property was built in 1980. You must provide sufficient
evidence to allow an auditor (or other reader of your notes) to be
confident in your decision. Did you see the deeds and photograph
them? Did the planning office provide a date? Did you rely on stylistic
clues and if so what were they?
The thermal
envelope
In order to calculate the heat loss of the property, the software needs
to know the area of the walls, the external wall thicknesses, the floor
areas, and the roof area (assumed to be the same as the floor area)
together with details of any insulation present. The assessor measures
these areas as well as the room height and the length of the heat loss
walls. The subject of property measurement is covered in detail later in
this manual.
Results of thousands of previous energy surveys allow the software to
accurately estimate the area of the windows for a property of any type
and age without the need to actually measure the windows, in most
cases.
It is necessary that the assessor follows the conventions so
that all DEA end up with the same result.
RDSAP Manual March 2012
U–values
DEAs using RDSAP are not required to calculate U-values, but some
understanding of them is important because the option of entering U
values directly to the software is available if the assessor is presented
with documentary evidence that fully supports the U values entered.
U-values are numbers with units of W/m2K (Watts per metres squared
Kelvin), e.g. 0.35 W/m2K. The U-values tell us the rate of heat loss of a
wall, window, floor, etc.
A built element with a larger U-value will have a higher rate of heat
loss, so the built element will ‗leak‘ heat more quickly. The heat loss
through the fabric of the building depends upon the construction
method; material and thickness of each part of the envelope; and upon
the area of that part.
By collecting descriptions of the building age and construction, the
energy rating software can assign a suitable rate of heat loss and Uvalue to each built element of roof, wall, floor etc. It can do this
because the U-values are usually characterised by the building
procedures of the period and (since 1966) by the energy design
standards demanded by successive upgrades of modern Building
Regulations. However, what the software needs to know is whether any
changes to the insulation standards have occurred since the property
was constructed. So for instance, a house built during the period of
1976–82 has an assumed wall U-value of 1.0. If the wall has had cavity
wall insulation fitted the improved U–value falls to 0.40, a reduction of
60%. Such an insulation upgrade will substantially improve the EPC
rating. RDSAP age bands are considered in Section Four of this manual.
Heating systems The annual cost of providing heating (including water heating) to a
home depends upon the amount of energy required to maintain the set
standard of comfort, after allowing for the heat losses, the efficiency of
conversion of energy to useable heat, the quantity of fuel needed to
provide the energy, and the price of fuel. It will also be reduced or
‗offset‘ by the presence of any renewable energy system.
Information is needed on the type of the primary heating system;
details of the primary heat source (e.g. the central heating boiler); the
fuel used (including for electricity–the tariff, i.e. on-peak or off-peak);
the use made of secondary space heating systems; the type of water
heating system; the type of hot water storage, if any; as well as types
of controls and renewable energy systems incorporated in the space
and water heating systems. Heating is considered in more detail later in
this manual.
RDSAP Manual March 2012
How does the software use the data?
The software
process
When the DEA enters data into the software, it then uses the input data,
combined with its built-in defaults, to carry out the calculations. The
output of this calculation is the predicted running cost for the home under
standard. The predicted running cost is then divided by the floor area of
the home and this figure is then converted into an energy efficiency
rating and an environmental impact rating, somewhere on the A to G
scale.
The calculation is then used to estimate the savings from installing
energy efficiency improvements, so that the energy advice report can
make recommendations for improving the home–and give a predicted
potential rating if they were to be carried out.
The Landmark
Register
The report is produced, reviewed by you and finalised when you are
happy that its content can be finalised. Once finalised you cannot later
change the report or its content. Once you are qualified, your EPCs will
automatically be lodged on the Landmark Register where all EPCs are
stored.
During training and assessment you will not be able to lodge reports and
do not have to worry about creating a ‗real‘ EPC for a property. You are
able to practice with the software as much as you need to.
RDSAP Manual March 2012
3.
Section three | RDSAP software
To Produce EPCs you need to use one of the softwares provided by different
accreditation schemes. All softwares use same conventions and methodology.
While training you will have access to a training account which will
allow you to use most of the features of EPC online but will stop short of
allowing you to produce ‗real‘ EPCs. You are able to practice with the software
without fear of actually creating an EPC for a property. The software that you
will use at this stage is essentially the same as the ‗live‘ software that you will
use once qualified.
Purpose of EPC
Marketed sale
This option should be used for EPCs required
for marketed sales (known as single survey in
Scotland).
Non-marketed
sale
This option should be used for ‗Right to buy‘ or
sales that are not advertised. For example the
sale of a house by one family member to
another.
Rental (social)
This option should be used for dwellings owned
by social landlords; this could be local
authorities or housing associations.
Rental (private)
This option should be used for rental EPCs from
the private sector. Institutions such as
universities will fall into this category.
Not sale or rental
This option should be used if the EPC
regulations do not require and EPC for the
dwelling, for example, if a homeowner wanted
an EPC just to see how energy efficient their
dwelling is.
There is a field on this page that asks if the report is ‗created from existing
data‘. This refers to the practice of cloning, whereby data is used from previous
EPCs. This practice is outside of the scope of this manual and requires
additional training. Further information may be gained by contacting NES.
Consequently that field and the next, which asks for a reference number,
should be left blank.
RDSAP Manual March 2012
General details
Here you are required to enter some fairly self-explanatory information about
the property such as the detachment, the number of storeys and the number of
extensions.
You will be asked whether you measured internally or externally.
Internal or
external
measurements
The measurements required are:
The floor area
The exposed perimeter
Room height on each storey
Exposed perimeter includes the wall between the dwelling and an unheated
garage or a separated conservatory and, in the case of a flat or maisonette, the
wall between the dwelling and an unheated corridor. Internal dimensions are
permissible in all cases.
When using external measurements for a dwelling joined onto another dwelling
(semi-detached and terraced houses) the measurement is to the mid-point of
the party wall. Flats and maisonettes are usually measured internally.
Whichever is chosen the same basis must be used for all parts of the dwelling.
Room heights are always measured internally within the room, from carpet
level to ceiling. The software automatically makes an allowance for the
thickness of intermediate floors.
RDSAP Manual March 2012
The ground floor area must not include any:
Integral or adjoining unheated garages (a heated garage is defined as
one which contains fixed heat emitters linked to a main/central heating
system)
Stores, coal sheds or other external (thermally separated) unheated
spaces
Thermally separated conservatories
Unheated, thermally separated porches
Terrain type
The terrain type must be recorded for every survey. This allows the software to
assume an average wind speed for the area. The average wind speed is used in
the calculation of the benefit of a micro wind turbine. Even if a wind turbine is
not present the terrain type must be recorded to enable the software to assess
whether a recommendation for a wind turbine is viable. See the table for the
choices and note that unless you are in a city centre location, suburban is the
most common choice.
Dense urban City centres with mostly closely spaced building of four
storeys or higher
Suburban Towns or village situations with other buildings well spaced
Rural
Mains gas
available
Open country with occasional houses and trees
If there is a gas meter at the property or a mains gas appliance then you need
to record that mains gas is available. The fact that there is a gas supplied to
other properties in the street does not mean that mains gas is available to the
property you are inspecting.
Number of rooms
and habitable
rooms
The software asks for the number of habitable rooms and whether any of these
are unheated.
RDSAP Manual March 2012
Habitable rooms include any living room, sitting room, dining room,
bedroom, study and similar; and also a non-separated conservatory.
A kitchen/diner having a discrete seating area also counts as a habitable
room.
A non-separated conservatory adds to the habitable room count if it has
an internal quality door between it and the dwelling.
Excluded from the room count are any rooms used solely as a kitchen;
utility room; bathroom; cloakroom; en-suite accommodation and
similar; any hallway; stairs or landing; and also any room not having a
window.
For open plan dwellings count all spaces thermally connected to the
main living area (e.g. a living/dining room) as one room.
For a kitchen to be a kitchen/diner it must have space for a table and 4
chairs.
A lounge/dining room where the door was temporarily removed (i.e.
architrave and hinges still there) is two habitable rooms.
A lounge/dining room with the door permanently removed (hinge holes
filled etc) is one habitable room.
Flats and Maisonettes
Note that flats are dealt with in more depth in Section Four.
Semi-exposed
elements
This page asks for details of the flat or maisonette you are entering and will
simply not apply if you are dealing with a house. If you are entering a flat you
will need to enter the flat type; that is whether it is a basement, a ground floor,
mid floor or top floor flat. You will also be asked to enter the flat‘s position in
the block. If it is a first floor flat, the floor position will be 1 and the software
helps you by providing the choices.
Under ‗semi-exposed elements‘ the software asks if there is a corridor and, if
so, what type and what length. A more detailed explanation of this and some
examples is contained within Section Four of this manual.
RDSAP Manual March 2012
Age and roofs
Unknown or asbuilt
Depending on the element, you will have the option of entering the insulation
as being ‗as-built‘ or ‗unknown‘. Using either will mean that the software
defaults to the insulation depth that apply according to the date you have
entered for the property‘s (or extension‘s) date of build. However, with
‗unknown‘ there will not be a recommendation for further insulation. (Take for
example a roof in a 1900 terraced house, over the page.)
If you are unable to access the loft you might enter that the loft insulation is
‗unknown‘. The software will assume the roof is insulated as it would have been
when new (in 1900 that would be none) and there will then not be a
recommendation for increasing the insulation. This is because the roof has not
been assessed for its suitability; there might be a condensation problem or
there might already be 300 mm of insulation. This does illustrate why it is so
important for the DEA to make every effort to inspect the roof space where
possible.
Choosing ‗as-built‘ for a wall for example, means the wall is as it was when
built. For a 2007 house ‗cavity walls as-built‘ means the walls are built to 2007
Building Regulations and will therefore be insulated.
Property age
Property age is extremely important to the software. The property age is
required for the software to select the default heat loss values (U-values) for
the wall, roof and floor and to calculate the window area. Clearly properties of
different ages will perform very differently and the general rule is that the
newer the property is the better the U values of its component parts. Houses of
different ages also have different window to wall and window to floor ratios.
The age bands for newer properties correspond to changes in Building
Regulations and the older age bands, pre-1966, with changes in methods of
building. The RDSAP age brackets are as follows and the job of the DEA is use
their best efforts to date the property accurately and place it in the correct age
band.
Age bands
Pre-1900
1967-1975 E
1996-2002 I
1900-1929 B
E 1976-1982 F
2003-2006 J
1930-1949 C
1983-1990 G
2007 onwards K
1950-1966 D
1991-1995 M
RDSAP Manual March 2012
A
Property age and how to date property is further covered in Section Four.
Roofs
RDSAP deals with roofs on the main property and any extensions. Each
is entered separately, starting with the construction type. Roofs types, their
insulation and the options available in the software are described in Section Five
page 24.
walls and floors
This section deals with walls and floors and their insulation levels. For both,
this is where you will enter the construction type, insulation type, insulation
thickness and any U values that are known. For walls the overall thickness of
the wall is required and whether there is a dry lining.
Note that walls and floors are covered in detail in Section Five.
Aalternative wall
This section of the software relates to alternative walls only and you will
simply leave the section untouched if there is not such a wall at the property.
You would enter an alternative wall type where the property has a significant
area of wall that is of different construction or insulation level than the
building part it belongs to, but this wall type cannot be identified as an
extension since it does not surround any floor area. Where an area of
alternative wall exists but it constitutes less than 10% of the total external
wall area of the building part it belongs to, it can be ignored.
The 10% of the wall area is identified including the windows and doors; it is
only when measuring to the area of wall calculate the area to be included into
the data summary that the area of any windows and doors is subtracted. This
means that if you believe there to be an alternative wall then you will have to
measure any window and door openings.
Alternative wall types can occur as part of the main house, or part of any
extension and you should record which of these applies. It is possible to enter
up to five alternative walls.
Note that alternative walls are dealt with in detail in Section Four.
RDSAP Manual March 2012
Left: The tile hung area of the wall might be
‗alternative‘, if you can determine its
construction to be different than that of the
rest of the house. In this example, it looks to
be approximately 10% of the total wall area,
but further measurement is required.
Dimensions
The software requires the following data for the main property and each
extension:
The floor area in metres squared.
The room height in metres to the nearest centimetre.
The heat loss perimeter (HLP) in metres.
See Section Four of this manual for detailed RDSAP measuring conventions.
Rooms in the roof
Note that roof rooms are dealt with in detail in Section Four. This section of the
software deals with rooms built within the roof space of a property and the
section will simply be ignored if there is not one at the property.
A room in the roof is a habitable room built into what would normally be a loft
space, above the main part of the dwelling, or above any extensions. Note that
for such a loft space to qualify as a room in the roof for energy assessment
purposes, it must incorporate fixed staircase access, i.e. not just a loft ladder.
It will usually have sloping ceilings for part of the area and may also include
dormer or Velux windows.
If a roof room is present, the software requires you to enter the age range,
floor area and the details of the insulation present. If you are able to obtain
documentary evidence of the U-values of the component parts, you can enter
this information in the extended data section on roof rooms (see Section Four).
RDSAP Manual March 2012
Openings
windows
Note that windows and glazing are dealt with in detail in Section Four. This
section of the software deals with the openings in the property created by
windows and also by any open fireplaces and ventilation systems. Details of any
draught proofing are also entered here.
The software asks that you enter whether the window area is typical of that
type of property or whether it is more or less than typical. It also asks that you
enter the proportion of the property‘s window area that is multiple glazed–if
any–and what type of multiple glazing is present.
if 60% of the area (including the frame) of a door is glazed, they are treated as
windows.
Open fireplaces
Ventilation
On the same page of the software in the ventilation section you are asked to
enter the number of open fireplaces. These contribute greatly to the ventilation
of the property and will remove some of the warmth generated by the heating.
Note that open fireplaces are dealt with in detail Section Four of this manual.
The software asks you to enter the ventilation method and the options are:
Natural ventilation–this means the property is ventilated in the
traditional way by windows and possibly vents in the walls and windows.
Mechanical, supply and extract–this is a whole house mechanical
system which both introduces fresh air into the property and extracts
heat from the stale air. Bathroom and kitchen extractors DO NOT qualify
as mechanical ventilation.
Mechanical, extract only–this is a whole house ventilation system
which mechanically extracts stale air from the property passive vents or
gaps in the fabric of the building. This is sometimes known as MEV.
Bathrooms and Kitchens extractors do not get classed as MEV.
Air conditioning
The presence of air conditioning in the property simply requires a box to be
ticked in the software.
Extended openings
This section is for use when there is much more or much less than typical areas
of glazing at a property and enables the location, dimensions, glazing type,
orientation, U value and g value of each window to be entered individually. See
also Section Five.
RDSAP Manual March 2012
Space heating
Main heating
systems
This important section of the software deals with the MAIN heating systems
within the property. It is possible to enter either one or two main heating
systems and apportion the amount of work each does in maintaining the
acceptable heating regime that was described earlier in this manual. The
―Product Database‖ which contains specific technical information on a wide
range of heating systems is located in this section of the software. Searching it
for a system just requires clicking on the appropriate tab.
A number of entries are required about the main heating systems and given the
complexity and range of possible entries, these have been covered in the
heating section of this manual (Section Six).
RDSAP Manual March 2012
Electric meter
See Section Four of this manual for more about electric meters.
The first entry to be made in this section is to describe the electric meters
present. The choices are:
Dual rate
Single rate
Unknown
24-hour
Heating systems
Details of any secondary heating system are required including the fuel and
system type. For a detailed definition of what a secondary heating system is
please see Section Six of this manual.
water and secondary heating
The secondary heating system should be entered next and this important area
is covered further in Section Six.
Details of the water heating system should be entered in this section of the
software, including the heating type, system, fuel and immersion heater type, if
applicable.
If there is a hot water cylinder, its size, insulation type and thickness and
whether there is a cylinder thermostat should be entered. This is covered in
more detail in Section Seven of this manual.
Bath and shower details are also recorded in this section, as follows:
Number of rooms with bath and/or ANY shower
Rooms with MIXER shower AND bath
Rooms with MIXER shower and NO bath
This enables the software to make the appropriate recommendations in respect
of waste water heat recovery systems (WWHRS).
Heat recovery systems
This section of the software asks for the number of waste water heat recovery
systems (see section 6 for details) and also allows for two flue gas heat
recovery systems (FGHRS) to be entered. Both systems have their own Product
Database which allows for searching for and selecting specific models.
RDSAP Manual March 2012
Conservatories and lighting
If a conservatory is present at the property, its type must be recorded and if
non-separated the floor area, whether double glazed, the glazed perimeter and
the number of storeys in height it covers should be entered.
See Section Four of this manual for a detailed look at conservatories.
Low energy
lighting
Low Energy Lighting includes CFL, LED and fluorescent tubular lighting. You
need to record:
The total number of fixed light outlets.
The total number of fixed low energy lights.
Section Four of this manual explains low energy lighting in more detail including
the conventions on counting combinations of lights.
Renewables
This section covers renewable energy systems; notably wind turbines, solar
photovoltaics and solar hot water. Renewables can require some complicated
software entries and these are covered in detail in Section 8.
Addenda
This section in the software enables the DEA to better describe the property‘s
features within the format of the report by allowing certain anomalies to be
explained to the reader. These include statements that explain that there are
wall types that do not correspond to the options available in RDSAP and the
presence of swimming pools.
This section is the last of the data input screens and clicking ‗next‘ at this point
will take you to the Results: Recommendations section.
The list of addenda is some optional statements that can be added to the EPC if
required. They describe situations which as yet cannot be modelled in the
software. The aim is to reduce complaints from householders about features
that are not adequately described on the EPC.
The list of addenda is currently as follows and is occasionally updated. In case
you are wondering why the list is numbered 1, 4, 5, 6, 8, 9, it is because the
missing numbers from this sequence represented addenda that have now been
removed from the list because the software has developed to the point where it
can deal with those issues. The screen shot below shows section P15 of the
RDSAP software which allows the assessor to select addendum.
RDSAP Manual March 2012
RDSAP Manual March 2012
Results: Recommendations screen
If you have fully completed each section so far, then at this point you will see a
SAP Result expressed as a figure between 1 and 100. Also you will see a list of
recommendations made by RDSAP.
If the property has walls of cavity construction, there are additional questions
about whether or not the cavity walls are ‗hard to treat‘. That is, whether there
are access issues such as adjoining conservatories, garages or other
outbuildings that might make the physical installation of cavity fill insulation
difficult. This could also include any situation where access by means of a 5 m
high ladder is not possible such as at higher buildings or flats. Cavity fill may
still be possible but will be more expensive.
Cavity walls which are within areas of high exposure may be subject to higher
levels of driving penetrating rain. The DEA should refer to the map below to
decide whether or not the property is in an area of high exposure and if so the
appropriate box should be ticked and an addendum generated.
Cavities which are less than 50 mm in width may require specialist cavity
insulation or may not be suitable at all. Ticking the box to say that walls have
narrow cavities will produce the appropriate addenda to inform the client of
this. Narrow cavities may be identified by a total wall reveal thickness of less
than 250 mm, yet a stretcher bond pattern to the brickwork.
RDSAP Manual March 2012
4.
Section four | Property features
Property features
introduction
Some questions contained within this Section only apply to flats and
maisonettes. Where this is the case, it will be clearly stated in the
text.
Some of the question titles (for instance, the number of rooms)
appear to request the obvious, but do make sure you read everything
through at least once, as there are a few points to remember.
Basements
A basement is defined as a part of the heated and occupied area of
the dwelling that is fully or partly below external ground level and
where 50% or more of the external wall area loses heat to the
adjacent soil rather than to the external air.
In order to be included within the energy assessment, a basement
must be accessed by a permanent fixed staircase such that a person
can walk down it facing forwards, and it is either:
Heated by fixed heat emitters, or
Open to the rest of the dwelling.
If recorded the basement will become the ground (or lowest
occupied) floor
.
Note that there do not need to be any habitable rooms present in the
basement.
When incorporating a basement in the assessment do not mix
internal and external measurements. If a basement is included in the
assessment, it is likely that internal dimensions will be used
throughout the dwelling.
RDSAP Manual March 2012
Bay windows
You are required to measure and enter details of all bay windows if
they increase the floor area of the property. If any of the building
elements of the bay are different to the rest of the house, i.e. the
walls, floor or roof, then you will need to enter the bay window as an
extension. Remember that an extension does not have to have been
built later. The ability to enter up to four extensions gives you the
flexibility to more accurately record such perturbations as bay
windows.
The bay in the photo is rectangular but bay windows can also be
either a trapezium shape or a semi circular shape. The following
diagrams should assist you in calculating the area of a bay window.
RDSAP Manual March 2012
RDSAP Manual March 2012
Conservatories
what is a
conservatory?
For RDSAP a conservatory is a structure with at least three quarters
of its roof and at least half its external walls glazed. If the structure in
question does not meet these requirements then it should be
considered as an extension. The treatment of a conservatory depends
on whether it is separated or non-separated from the dwelling.
separated or
non-separated
A separated conservatory is effectively ignored for the purpose of
calculating the dimensions and heat loss perimeters, although you do
need to note whether or not it has fixed heaters.
Most modern conservatories fall into this category; they will often
have external quality uPVC doors separating them from the house. As
a rule of thumb, if you imagine the conservatory was removed, you
would need to ask: Would the doors offer sufficient protection from
the elements?
External quality doors are usually thicker and have features such as
double-glazing, locks, bolts and weatherproof surrounds.
A non-separated conservatory will either have internal quality
doors–the thin, lightweight type that sometimes separate rooms, or
will be open to the adjoining room. The doors may have been
removed or the conservatory could have been designed to extend the
room and have no doors. Consider whether the non-separated
conservatory alters the number of habitable rooms.
Several items of data are required about the non-separated
conservatory:
Floor area, measured internally
Glazed perimeter (ignore areas of brick wall)
Whether double glazed
Conservatory height in storeys
RDSAP Manual March 2012
Images 1 and 2 show an example of a separated conservatory,
with sliding ‗patio‘ doors. These are of exterior quality, are double
glazed, provide a good seal, and are lockable.
Images 1& 2: Exterior quality door–note they provide a good seal, are heavy
weight and lockable.
Images 3 and 4 are of a non-separated conservatory. The interior
quality doors are not deemed to thermally separate the conservatory
from the main dwelling. Although it is not visible from the images,
these do not close properly owing to the lack of wooden trim to the
frame, the latches are missing and they do not lock.
Images 3 & 4: Interior quality doors–note they do not shut properly and do not
provide a good seal to the doorway.
RDSAP Manual March 2012
To recap: In RDSAP there are four options for conservatories:
A non-separated conservatory is like an extension in that the heat
loss perimeter of the house does not include the length of house wall
next to the conservatory. This is illustrated in the diagrams below.
Conservatory
No conservatory
No conservatory present either separated or
un-separated.
Separated
conservatory,
no fixed heaters
A separated conservatory is present, but
there is no heating or only portable heating
Separated
A separated conservatory is present and is
conservatory,
heated by fixed heaters which may be from
fixed heaters
the main heating system.
A conservatory that is open to, or separated
Non-separated
Data for nonseparated
conservatory
conservatory
by internal quality doors, the main dwelling.
Record the area, height, glazed perimeter
and whether it is double glazed.
The exposed perimeter for the conservatory should be measured in
the same way as for the main house and extension but it is the
length of exposed glazed wall that is required. If there are areas of
brick wall, these can be ignored. This is illustrated in the diagrams
below.
Remember to indicate if the conservatory is double-glazed and to
estimate the average height of the conservatory relative to the main
dwelling storey height.
RDSAP Manual March 2012
example 1:
In this case, the
conservatory floor
area is 15 m2 and
the glazed
perimeter is 11 m.
House with a non-separated
conservatory
House heat loss perimeter is: 6
+ 6 + 9 + 4 = 25 m
Conservatory glazed perimeter is
3 + 5 + 3 = 11 m
Conservatory floor area is:
3 x 5 = 15 m2
In this case, the floor area is 15 m2 and the glazed
perimeter is 11 m.
example 2:
In this second
example, the
conservatory floor
2
area
is 12 m and
the glazed
perimeter is 7 m.
House with garage and nonseparated conservatory
House heat loss perimeter is:
6 + 8 + 6 + 5 = 25 m
Conservatory glazed perimeter is
3 + 4 = 7m
Conservatory area is
3 x 4 = 12 m2
RDSAP Manual March 2012
It is important to note that when calculating house floor areas and
that you do not include within these the area and glazed
HLPs perimeter of the conservatory.
what if the
conservatory is
not a
conservatory?
It is not uncommon to find a ‗conservatory‘ that does not meet the
RDSAP definition of such; i.e. a structure that does not have half its
walls and three quarters of its roof glazed. Garden rooms may have
a traditional flat or pitched roof. In these circumstances the
structure should be treated as an ordinary extension except that you
may need to make use of the ‗more than typical‘ glazing feature of
the software which is discussed in the section on windows further on
in this Section.
passive solar
design and sun
rooms
Separated conservatories provide shelter to the external wall, and
also capture solar heat, which will partially warm the house.
For most conservatories this effect is very small and both the solar
heat gain and the sheltering effect are ignored in the RDSAP energy
rating calculation.
Some homes have exceptionally large unheated conservatories
covering more than one storey and designed as a ‗solar space‘ to
deliberately capture solar gain and pre-warm the home.
These properties can be recognised by the fact that the
‗conservatory‘ will often extend to the full height of the dwelling and
will make up a large proportion of the dwelling floor area. This can
be dealt with by using one of the ‗more than typical‘ glazing options–
see the section on windows. An example is shown in the image
below.
RDSAP Manual March 2012
Detachment
Whether the property is detached, semi-detached, terraced or built in
another form is important to the software so that it can select the
appropriate set of default assumptions, including the pattern of
window openings/glazing that should apply. Your choice of
detachment will appear on the front of the EPC report. The options
are described below.
Detached
Houses that are described as ‗detached‘ have no party walls and so
have exposed wall area on all four sides. Here are some examples.
Link detached houses (houses that are essentially detached and are
only linked to neighbours by a garage) should also be classed as
detached.
semi-detached
Semi-detached houses share one side (the party wall) with a
neighbour. This leaves exposed wall area on three sides.
Although end-terrace and semi-detached properties are similar in
terms of exposed walls there is a slight difference in the typical
window areas for the two built forms. An end-terrace property will
usually have a blank gable end wall, where as a semi-detached house
will most likely have additional glazing in the side elevation, being
glazed on three sides, rather than just front and back.
RDSAP Manual March 2012
End-of-terrace
Mid-terrace
As the name suggests this is the first or last house in a terraced row.
End-of-terrace properties have three exposed sides like a semidetached, but tend to have blank end walls. This means that the
typical pattern of glazing will be the same as for a mid-terrace.
Mid-terrace houses have two party walls (one on either side) and two
heat loss sides (front and back).
If the terrace has a passage through to the back of the house,
classify it as a mid-or end-terrace house, include the length of the
passage wall in the lowest floor heat loss perimeter and consider
identifying the heat loss floor above the passageway through the
‗extension‘ option.
Enclosed midterrace
These houses are often called ‗back-to-backs‘. Back-to-back
properties are essentially terraced houses that also back onto another
terraced row. From the street they will look just like a terraced
house, but the rear of the property joins the back of a house from the
next street, which gives us the phrase ‗back-to-back‘. They have only
one heat loss wall, as the side walls are common with their
neighbours and the rear wall is common with the property on the
terrace of houses at the rear.
RDSAP Manual March 2012
Be careful if a house is described to you as ‗back-to-back‘–sometimes
this term is used to describe terraces that are built very close
together with only a narrow yard separating them. These back-tobacks are not enclosed, they are normal terrace houses.
Enclosed end
terrace
An enclosed end-terrace will be the first or last house in a terraced
row of back-to-back houses. They have two adjacent heat loss walls,
and two adjacent party walls.
Modern ‗cluster‘ homes are also enclosed end-terraces; the block is
essentially four enclosed end-terraces without any mid-terraces in
between.
A residential
property adjacent
to commercial
premise
It is possible to record a dwelling next to a shop or office in the
following way:
If a dwelling has a commercial property below, record as
‗partially heated space‘ below.
If a dwelling has commercial premises above, record as ‗other
dwelling above‘.
If a dwelling has commercial premises alongside it, treat as a nonheat loss wall.
RDSAP Manual March 2012
Dimensions
Introduction
Property dimensions are an important part of the energy rating
calculation–remember that the energy rating is calculated by dividing
the predicted fuel costs by the floor area so it is important that the
floor area is calculated accurately. Your floor area calculation is
displayed on the front page of the EPC.
The heat loss perimeter (HLP) is needed to assess the heat losses
through the building fabric and the room height is important, since
the ventilation loss depends on the building volume, which is
calculated using the room height.
For a simple property such as a bungalow or a flat, the actual data
entry could be as few as three items–floor area, room height and heat
loss perimeter. For many houses, the floor area and HLP will be the
same on all floors (but not the room height!), so the amount of data
to input is often less than you might think. However, there are
properties where the measuring can be more complicated. Imagine
an irregularly shaped house with numerous extensions, bay windows,
conservatory, etc; in such a case there is considerable measuring to
do which will require a systematic approach.
Floor plans
A floor plan showing dimensions (and other property features) is
essential in every case, even the simple properties. The plan should,
among other data items, show the horizontal dimensions of the
property, the room heights and the HLP.
It is highly recommended that you highlight the HLP with a different
colour, firstly to aid you in ensuring accuracy and secondly to allow
someone checking your work to be able verify your accuracy.
: A well-marked floor plan: The plan should also show the position of
lights, windows, heat emitters and anything else that is relevant to the
inspection.
RDSAP Manual March 2012
Internal or
external
measurements
For houses, internal or external dimensions can be used depending
on which are easier to measure on site. If you measure externally,
the program uses those external dimensions by adjusting them to
allow for the wall thickness, but the entire survey needs to be carried
out using either internal or external dimensions.
Flats are usually measured internally, as is room height and room in
roof floor area.
You must not change between internal and external when measuring
different parts of the house.
Floor area
At a straightforward rectangular property, the floor area is calculated
simply by multiplying the length of the property by the width.
By using external measurements you will be calculating the Gross
External Floor Area (GEA) and by using internal measurements the
Gross Internal Area (GIA). The software adjusts whichever you
decide to use to GIA for the EPC report.
Complicated properties will require more dimensions to be taken on
site and a more careful and detailed approach to making an accurate
calculation.
Do not include external unheated porches in the floor area.
Do not include unheated areas (such as outhouses, outside toilets,
garages or coal stores) that are not accessed via an internal door,
even if they are within the footprint of the dwelling.
Do include unheated rooms, e.g. internal utility rooms and lobbies,
so long as they are within the external envelope of the property and
are accessed via an internal door.
Heat loss
perimeter
The external or internal dimensions are used to work out the exposed
wall perimeter. The exposed wall (heat loss perimeter or HLP) is
extremely important for evaluating heat loss wall areas as well as the
heat loss through the ground floor. Therefore it is essential that it is
measured accurately. The energy assessor is required to record the
heat loss perimeter (HLP) for the main house and, separately, for any
extensions. The heat loss perimeter must also be calculated for each
floor of the house and any extension(s) present.
RDSAP Manual March 2012
For mid-terrace dwellings with a side passageway, the length of
passageway wall is part of the exposed wall and its perimeter should
therefore be added to the measurement for the exposed perimeter
for the dwelling.
Where there is an integral garage, or an attached garage, or any
other external construction such as an outhouse adjoining the
external wall of the dwelling, the perimeter of the house next to it is
counted as part of the heat loss perimeter. This is because there will
always be heat loss through the wall into the unheated space.
Although the heat loss will be slightly reduced by the sheltering effect
of the garage, this reduction in the heat loss through the wall is
considered to be insignificant for RDSAP. So, the heat loss through
the sheltered wall is calculated as if the garage or other external
construction were not there.
Enter separately the heat loss perimeter of any extensions–this is
illustrated in Example 2. An example of an extension on the upper
floor only is given in Example 3.
For roof rooms, the heat loss perimeter is not required, since it is
assumed that there is no heat loss wall on this storey. The software
assumes that all the heat loss is through the roof/stud walls and
calculates the areas of heat loss roof appropriate to a roof room
construction, without need for a heat loss perimeter measurement.
Example 1:
Two storey house
with integral
garage.
Ground floor area is
(8 x 3) + (6 x 5) = 54 m2
First floor area is
(8 x 9) = 72 m2
Ground floor heat loss perimeter
is 8 + 3 + 3 + 6 + 5 = 25 m
First floor heat loss perimeter is
8 + 9 + 8 = 25 m
RDSAP Manual March 2012
Example 2:
Two storey
detached house
with single storey
extension.
Ground floor area is
8 x 6 = 48 m2
Extension floor area is
5 x 3 = 15 m2
House ground floor heat loss
perimeter is
6 + 8 + 6 + 3 = 23 m
House first floor heat loss
perimeter is
8 + 6 + 8 + 6 = 28 m
(note: this is 5 m longer than
the ground floor, i.e. the length
of wall between the house and
ground floor extension)Extension
exposed perimeter is
3 + 5 + 3 = 11 m
Example 3:
Two storey
detached house
with extension over
garage.
House ground floor heat loss
perimeter is
6 + 8 + 6 + 8 = 28 m
House 1st floor heat loss
perimeter is
6 + 8 + 8 + 2 = 24 m
(note: this is 4 m shorter than
the ground floor, i.e. the length
of wall between the house and
extension–not a heat loss wall)
Extension heat loss perimeter is
3 + 4 + 3 = 10 m
RDSAP Manual March 2012
Measuring
perimeters when
access is
restricted
There may be occasions where a part of the HLP for a dwelling is
unable to be accessed. The below photo is an example where some of
the HLP runs into the neighbour‘s garden and from the inside it is
impossible to tell where the party wall ends and the external wall
starts.
Above: Heat loss perimeter in neighbour‘s garden.
In order to obtain a measurement of this stretch of wall the only
option available is to count the bricks. By measuring a single brick
(including mortar) and counting the total number of bricks on this
piece of external wall on the dwellings perimeter. The internal
measurement would be required, so the thickness of the reveal from
the patio doors would be subtracted to give a total.
Room heights
Room height is an important dimension because it enables the RDSAP
software to calculate the volume of the property accurately. You
should measure to the nearest centimetre.
The energy assessor simply has to record a single dimension for room
height on each level of the property. This is often as simple as
measuring from carpet level to the underside of the ceiling and the
room height will often be the same in all the rooms on that level (a
few check measurements may confirm this). If there are extensions
then a room height dimension will be required for each extension and
these may well be different to the main house.
Do not add on any allowance for the depth of the floor structure or
the ceiling structure above since the software already automatically
adds an amount to allow for this.
RDSAP Manual March 2012
Area weighted
room heights
Where a storey has a number of rooms with different ceiling heights,
as is sometimes the case with older properties, you can calculate the
area weighted room height for the whole storey.
Total storey area = 50 m2
Room 1: 15 m2 with room height 2.2
Room 2: 10 m2 with room height 2.3
Room 3: 10 m2 with room height 2.4
Room 4: 15 m2 with room height 2.5
[(15 x 2.2)+(10 x 2.3)+(10 x 2.4) + (15 x 2.5)] / 50 = 2.35
Sloping ceiling
Another scenario is where a storey has sloping ceilings and you need
to calculate an average room height; for example where a vaulted
ceiling exists in a roof space (but does not qualify as a roof room).
In this example you need to split the room into three sections as
illustrated. The two sections at either end can then have their
average height calculated: (2.0 m + 3.0 m) / 2 = 2.5 m
The room height of the main centre section is 3.0 m. The overall
average room height can then be calculated by averaging the
separate section heights based on the overall room width
(1m + 4m + 1m):[(2.5 x 1.0)+(3.0 x 4.0)+(2.5 x 1.0)]/6 = 2.83 m
RDSAP Manual March 2012
Galleried
rooms/balconied
bedrooms
Dwellings that have balconied bedrooms and double-room height
rooms are dealt with in a particular way by RDSAP. The following
schematic drawing depicts one type of this situation.
The property is a mid-terrace with one bedroom on the upper floor.
The upper floor is balconied and open to the rest of the property and
only covers 50% of the ground floor area. The room height of 50% of
the ground floor is 4.9m. In order to input this property, the area
weighted room height for the ground floor needs to be worked out.
Even though the dwelling is totally open-plan, treating the house as a
single (very high) storey will not calculate the SAP correctly as it
omits the upper floor area. In the SAP the floor area is integral to
many of the calculations, such as hot water requirements and the
zone 1 area. Therefore it is crucial that this additional floor area is
included.
2
2
2
20.00m x4.90m220.00m x2.40m
 3.65m
20.00m 20.00m
Thus, the input into the RDSAP dimensions
should be:
RDSAP Manual March 2012
and NOT:
Extensions
introduction
The energy assessor is required to identify any extensions at the
property and up to four extensions can be recorded.
The first thing to remember about the term ‗extension‘ is that this
does not always mean a part of the house that has been added on to
the main house at a later date.
In RDSAP terms, an extension is any part of the heated and occupied
area of the house that is ‗thermally different‘. By this we mean that it
has been insulated to a different standard or has a different built
construction from the main part of the house. The word ‗extension‘ is
in a sense slightly misleading.
An extension will usually be a part of the property that has been built
at a later time. However, it could also be because an occupant has
insulated part of a house (rather than the whole property); or a part
of the original construction might be thermally different (e.g. a mono
pitched roof single storey off-shot washroom at the rear of a
Victorian terrace).
Ask yourself if there is a significant feature that makes part of the
property different to the rest and therefore justifies classing it as an
extension. Are the roof, walls or floors different? Is there a significant
difference in room height in one part? Is one part insulated and one
part not?
splitting the
property
Entering a section of a dwelling as an ‗extension‘ can be a useful way
to artificially split a property to reflect the different thermal
properties of different parts of the same property. For example,
where two halves of a property have significantly different room
heights the property can be artificially split in two–the differing room
heights entered for each half. There is no reference made to ‗main‘
and ‗extension‘ on the EPC, so this will not lead to confusion for the
customer. However, make sure to record in your site notes why you
have artificially split the property.
Entering the property into the software as having an extension allows
the effect of different levels of insulation to the walls or loft/roof to
be described separately. This gives the software a more accurate
description of the property, and so increases the accuracy of the
energy rating.
For instance if a house has a pitched main roof, and part flat roof,
this should be entered as a ‗main house plus an extension‘ even if
RDSAP Manual March 2012
the roofs were built at the same time. The ability to use up to four
extensions presents a means of quite accurately accounting for the
various parts of complex larger properties.
The entries for extension dimensions, age, wall and roof details are
all separate from the main house details and there are appropriate
sections of the software in which to record them. However, the EPC,
once finalised, will not necessarily show the reader details of all of
the extensions. If elements of an extension are considered too small
to warrant inclusion (a 10% rule applies), they will feature in the
background calculation but will not be mentioned in the EPC report.
Note that on rare occasions you will come across a property that you
think cannot be fairly described using the extension fields (maybe
because it has too many different types of construction). In such a
case where you believe you could need more than four extensions it
will be necessary to combine extensions so that the number is
reduced to four. When doing this, you should combine those
extensions that are closest to each other in terms of their
construction and insulation.
For example, it is often possible to combine extensions from adjacent
age bands. There is no difference in heat loss between an uninsulated loft from a house built in 1930-1949 and the same loft built
in 1950-1965, but there is a big difference between un-insulated and
insulated lofts of the same age band.
Vertical extension It is possible to enter a new (or thermally different) upper floor to
the software as a vertical extension. An example of this might be
where a new floor has been built above what was previously been a
bungalow.
RDSAP Manual March 2012
Flats and Maisonettes
For RDSAP a flat is a single storey dwelling located within a block
containing at least two storeys.
A maisonette is simply a flat that extends over more than one
storey. It can still be part of a small block or a high-rise block.
Flats require some additional items of data to be collected on site
that don‘t need to be recorded for houses.
Floor position for
flats
The floor position is simply a number that identifies on which storey
of the block a flat or maisonette is located. The floor position number
is easy to remember as it starts at zero for the ‗ground‘ floor. It
follows that the first floor has a storey number of one, and the
second floor a storey number of two etc.
The floor position is used to work out the height of the flat and
therefore the level of exposure to the wind (greater at higher storeys
than at ground level). So even if the ground floor of a block of flats
contains no dwellings (e.g. it may contain car parking or communal
areas) this floor is still counted as zero.
RDSAP treats a maisonette in exactly the same way as a flat so we
refer to them as flats in this manual, but note that it is the lower
floor of the maisonette which identifies its floor position.
Basement level
In some instances, a block of flats may incorporate ‗basement‘ levels,
which may or may not include dwellings. In these circumstances the
‗bottom-most‘ of the basement levels should be identified as the
‗Ground‘/Level 0 ‗storey‘, with consecutive numbering from this point
upwards as before. Therefore, the Ground/Level 0 storey will always
be the bottom-most level in any block and will have a floor that is in
contact with the ground, i.e., no further space below.
RDSAP Manual March 2012
RDSAP Manual March 2012
Flat type
The software also requires the flat type (basement, ground, mid-or
top floor) and the floor position within the block. For example, a flat
on the second floor is entered as: flat type mid floor flat; floor
position 2).
Additional data for flats (and maisonettes)
introduction
Corridors next to
flats
A few extra items of data are required for flats, since flats sometimes
have heat losses from exposed floors, unheated corridors and
stairwells which are not usually associated with houses. For
maisonettes, use the same conventions as for flats.
Flats often have walls separating the occupied floor area from
common areas, such as corridors, lobbies or stairwells. For
simplicity the survey form refers to all of these as ‗corridors‘. The
heat losses from the flat into the common areas obviously depend on
whether the corridor is heated or unheated. The survey form
therefore requires you to tick one of the following:
No corridor
Unheated corridor
Heated corridor
And in addition for unheated corridors:
Length of sheltered wall (if unheated corridor)
The relevant section of the survey form is shown below.
The amount of shelter from an unheated corridor within a building
split into flats is more significant than the shelter provided by
garages or conservatories. Additionally, in a flat, the area of wall that
is sheltered is usually a larger proportion of the total heat loss wall
area. This is why it is necessary to separately enter semi exposed
RDSAP Manual March 2012
wall lengths for flats, but not for houses and bungalows.
If there is a heated or unheated corridor, it normally covers the main
entry door into the flat. This helps to stop heat losses when the door
is open–this is generally called a ‗draught lobby‘. A flat whose front
door opens directly to the outside of the building allows heat to
escape whenever it is opened, and the draught lobby reduces this
effect.
Remember that the length of the unheated corridor must be included
in the heat loss perimeter of the flat.
The wall that separates a flat from the adjacent corridor may be of a
different construction than the other perimeter walls of the flat. If
Corridors next to
flats as an
this is the case, the wall can be classed as an alternative wall. This
only applies when the corridor is unheated.
alternative wall
Flats with a small
entrance area
For flats or maisonettes where there is a small entrance on the
ground floor that is not separated by an external quality door the
following procedure applies. Divide the flat into main and extension,
where the flat on the upper for is the main and the small entrance
area is the extension, the extension is likely to be two storeys.
Flats: heat loss floors
heat loss floor
As with houses the heat loss floor type needs to be collected.
Exposed floor: is above an open airspace, e.g. an archway
to courtyard etc.
Semi-exposed (unheated): above an unheated internal
area (internal car park, unheated store etc.)
Semi exposed (part heated): above a space heated to a
lower temperature, or heated at different times to the
dwelling concerned. For example, a flat located above a shop
or an office.
Other dwelling below: there is another flat below and the
assumption is that there is not heat loss between the two.
Ground floor: is in contact with the ground.
RDSAP Manual March 2012
Habitable room count
introduction
The energy assessor is simply required to enter the total number of
habitable rooms in the entire property. Arriving at this figure,
however, requires some understanding of what a habitable room
actually is. The habitable room count field is used to estimate the
proportion of floor area that is heated to a higher temperature than
the rest of the dwelling. The energy rating model assumes that zone
1 (typically the lounge and any areas open to it) is heated to 21о and
the rest of the house (zone 2) to 18о.
The habitable room count does not directly identify this area but is
used to infer the zone 1 ‗fraction‘ assumed by the software. The
greater the number of habitable rooms, the lower the zone 1 fraction
assumed.
The number of habitable rooms counted is important to the energy
rating because more output is needed from the heating system to
heat to a higher temperature, and heat losses are greater from the
better heated rooms, i.e., the higher the zone 1 fraction, the greater
the dwelling temperature.
To count the required number and type of habitable rooms in a
property, include any living room, sitting room, dining room, kitchendiner, bedroom, study and similar. Exclude other rooms such as any
kitchen, utility room, bathroom, cloakroom, en-suite accommodation
and similar; any hallway, stairs or landing; and also any room not
having a window, or source of natural light.
For open plan dwellings count all spaces thermally connected to the
main living area (e.g. a living/dining room or non-separated
conservatory connected to the living room) as one room. For
example, a typical small two-bed mid terrace property might have six
‗rooms‘ in total, made up of the following:
Lounge/diner
Kitchen
Master bedroom
Second bedroom
Bathroom
Hall, stairs and landing
In determining the habitable room count for RDSAP, the hall, stairs
and landing, bathroom and kitchen are not included and the room
count is therefore 3.
RDSAP Manual March 2012
The lounge/diner counts as one room, even if it has been created by
removing a separating wall e.g. opening up a through lounge.
Non-separated conservatories should be included in the habitable
Conservatories as
room count depending on the presence of internal doors separating
habitable rooms
the conservatory from the main dwelling (conservatories will be
explored in more detail later in this Section).
If the conservatory is divided from the main property by internal
doors, then it should be included in the habitable rooms count
(assuming it is of habitable type, although it is unusual to find a
conservatory that is solely a bathroom or kitchen etc.). If the
conservatory is unheated, it should be classed as an unheated
habitable room.
If there are no doors between the conservatory and the main house,
the conservatory effectively becomes part of the habitable room that
it is adjacent to, therefore the habitable rooms count remains the
same.
kitchen or
kitchen/diner?
For a kitchen (non-habitable room) to be identified as a kitchen/diner
(habitable room), the requirement is that it must contain a discrete,
separate area large enough for a dining table and chairs. A kitchen
with a breakfast bar would therefore not qualify as a ‗habitable‘
room.
Room count: include only the types of ‗habitable‘ rooms as
described above.
RDSAP Manual March 2012
Porches
RDSAP distinguishes between two types of porches:
Internal porches
External porches
For RDSAP, a porch is defined as a small entrance area, which has
doors at either end. Porches which are under the main roof of the
dwelling, within its ‗foot print‘, are deemed part of the main building
structure and are referred to as internal porches.
The start position for assessing internal porches is that all internal
porches are included in the assessed floor area, whether heated or
unheated. However, if it is possible to identify the type of separation
between the porch and the main dwelling the following conventions
should be used:
Include all heated internal porches, i.e. those with fixed heat
emitters.
Include all unheated internal porches (unheated includes
those heated with portable heating units) that are not
thermally separated from the main dwelling, i.e. have
internal door separation only.
Exclude all unheated internal porches that are thermally separated
from the main dwelling, i.e. those that have external door quality
separation from the main dwelling.
External porches
For RDSAP an external or ‗off-shot‘ porch is an entrance area (with
doors at either end) built outside of the footprint line of the main
dwelling. It may appear to be ‗added on‘ to the front of the property.
External porches should be included if heated. It is highly likely that
they will need to be considered as extensions because it is rare that
you will be able to access the porch roof to be able to assess its
insulation. The wall or floor construction may also be different to the
RDSAP Manual March 2012
main house.
External porches (with a door at each end) can be ignored if
unheated regardless of the quality of the door separating it from the
main house.
Property age
introduction
The property age is extremely important to the software. It is
required for the software to select the default heat loss values (Uvalues) for the wall, roof and floor and to calculate the window area.
Clearly properties of different ages will perform very differently and
the general rule is that the newer the property is the better the U
values of its component parts. Houses of different ages also have
different window-to-wall and window-to-floor ratios. The age bands
for newer properties correspond to changes in Building Regulations
and the older age bands (pre 1966) with changes in methods of
building.
The RDSAP age brackets are given in the table and the job of the
energy assessor is to use his best efforts to date the property
accurately and place it in the correct age band.
It is important to note that RDSAP makes certain generalisations that
may not always be strictly accurate in all cases. For example, you
may find houses built post-1983 that DID NOT have cavity wall
insulation fitted when they were built, even though RDSAP assumes
it to be so.
It is very important to record clearly how you dated the property.
There will be times when you have exhausted all the easy means of
doing so and are forced to resort to an estimation based on stylistic
clues. Recording your methodology will serve to defend your decision
if you are later found to be incorrect.
RDSAP Manual March 2012
Age band
A: Pre-1900
Significance of the age band
Properties in this age bracket are usually easy to date purely on stylistic
features.
B: 1900-1929 Properties in this age band do not perform thermally significantly
different to those in the pre-1900 band.
C: 1930-1949 Cavity walls became the norm. Larger bay windows semis became
popular.
D: 1950-1966 This period saw a major boom in housing development and bungalows.
Still no insulation to the fabric of the houses.
E: 1967-1975 1966 saw the introduction of the modern building regulations and the
first tangible moves towards conserving energy in homes. This is the
first age bracket that assumes lofts to be insulated.
F: 1976-1982 RDSAP assumes that cavity wall thermal performance improved
significantly through the use of thermal concrete blocks and sometimes
insulation. Cavities are assumed to be empty and capable of being
retro-fitted with insulation. Loft insulation levels are assumed to
increase. Extraction assumed; suspended timber floors sealed.
G: 1983-1990 RDSAP assumes that cavity wall thermal performance improved still
further in this age bracket and no further recommendation is made for
cavity wall insulation. Loft insulation depths increase further.
H: 1991-1995 RDSAP assumes that cavity wall thermal performance improved still
further in this age bracket with a significant improvement in their Uvalue. Loft insulation depths increase still further.
I: 1996-2002 RDSAP assumes that floors began to be insulated during their
construction in this age bracket.
J: 2003-2006 The performance of double-glazing improved significantly post 2002.
Hot water separately timed.
K: 2007
onwards
All aspects of properties improve in terms of thermal performance.
Primary pipe work insulated.
RDSAP Manual March 2012
How to date a
property
There are various ways of establishing the age of a house or flat. It is
best not to rely on a single piece of evidence but rather to use other
means to corroborate where possible. Property age is one of the most
important factors in the EPC calculation.
It is worth noting that the date you input does not appear on the EPC
for the client to see, but is part of the calculation in the background.
You can ask the occupants. There is a good chance they may
know but don‘t be surprised if they don‘t or if they are shown
to be mistaken. Don‘t assume that people are always telling
the truth. In some cases people can provide you with
documentary evidence of completion of conversion or
renovation work, even a NHBC certificate in the case of fairly
new homes. If you ask people in advance, perhaps when
calling to make the appointment, to prepare any documents
they have, you are more likely to get to see them.
Ask the estate agent, if there is one, or the housing
association. If there is a solicitor involved in the transaction,
they may help you, particularly if you already have a working
relationship with them. Again, verify any information where
possible.
If you see an elderly neighbour or resident walking past, ask
them (tactfully) when the properties were built. Older people
are often very knowledgeable.
Contact the local authority, particularly the planning archive
team who are often helpful. Once you identify a helpful
person, make a note of their name for next time.
Use the internet. Google the postcode. There are websites
such as Mouseprice.com that will often give you dates for
houses or even whole streets and rely on surveyors and
valuers to update them with new information.
The Land Registry is a good source of copies of original deeds
and plans of properties and will usually provide a date of
build. However, there is a small charge which may be
prohibitive. Your company may have access in some cases.
Older properties are easier to date and arguably less critical.
You simply have to place them in the pre-1900 age band so
you are not overly concerned whether they are built in 1700
or 1899. There is not much thermal difference in properties in
the next age band, 1900-29, and if unsure which of these two
RDSAP Manual March 2012
bands to use you should test the difference with each using
the RDSAP software. If there is no difference in the ratings
you are safe to use either, probably using the worst case.
For modern houses the date becomes much more important.
Changes in thermal performance are significant between the
RDSAP age bands. There are clues connected with Building
Regulations. For instance the 1990 regulations introduced
extract fans, and trickle vents into windows. If the house
does not have these it may be before the 1990–95 age band.
Be cautious using this rule, as the windows might have been
replaced recently.
Dating by stylistic features can be very tricky to do and you
can easily get it wrong. Roof pitches were sometimes
shallower in the 1970s, a period which also saw chimneys go
out of fashion, to return in the early 1990s. Making an
informed estimate based on style–looking at the whole street,
not just the house being inspected, can be useful, although
beware of the recently built ‗infill‘ property. Look at the
windows on the neighbours‘ houses. Stylistic clues can be
misleading, so try to take a few into consideration.
The photographs on the following pages give some indication of
stylistic clues to help you date properties based on their appearance.
RDSAP Manual March 2012
pre1900s
This age band contains the Georgian (1714-1830) and Victorian
(1837-1901) housing stock which in some areas forms a large
percentage of the total housing. Often these houses of different
styles and ages are found near the town centre, built from local stone
with stone roof tiles. Many have, of course, been substantially
modernised.
A summary of the characteristics of these houses:
The use of local materials, e.g. local stone, brick or timber
frame.
Brick bonds typical of solid walls, e.g. Flemish and English
bonds.
The original windows would often have been wooden sliding
sash windows, with smaller panes of glass usually indicating
an older house and larger panes meaning a house late in this
RDSAP age bracket.
Car parking was not a consideration with these early houses.
This means that the roads are now very congested by onstreet parking.
The solid brick walls of these houses are often rendered.
RDSAP Manual March 2012
1900to1920s
This age band includes the Edwardian (1901-1910) housing stock
which took many of its stylistic features from the Victorians.
Thermally, there was no significant improvement in the buildings.
Insulation was not really a consideration yet. Window glass was now
being manufactured in larger sheets, but essentially the windows still
appeared Victorian in many cases. The brick walls still tended to be
solid, i.e. not cavity construction. The example above shows the
decorative use of engineering bricks, sometimes used to improve the
foundations and reduce rising damp. Hallmarks of Edwardian (or late
Victorian) houses:
Solid front door with fan light above.
Decorative supports for window sills.
Tiled floor to the porch.
Closer inspection reveals 9 inch (230 mm) thick walls.
The classical features of some of the Victorian houses made way for
the Gothic revival of the Edwardian period. Typical features include:
Decorated gables (e.g. on the semi-detached house below
c1910).
Sash windows with large panes, often one pane above and
one below the meeting rail.
Glazed doors are common.
RDSAP Manual March 2012
1920s
Not much house building had gone on during World War I, and the
period afterwards was very significant in the development of housing
in Britain. It saw the first ‗council housing‘ and there was a great
emphasis on ‗social housing‘. The 1920s saw housing influenced by
the Art Deco movement.
A ‗70 ft rule‘ governed the minimum distance between houses,
reducing density dramatically: from 20-30 houses per acre (common
in Victorian and Edwardian terraces) to as few as 6-8 houses per
acre.
House building immediately after the first world war was much
influenced by the garden city movement and the Tudor Walters
report. Typical features of this period:
Spacious, detached, semi-detached and terraced houses.
Equally spacious hedge lined plots in an estate layout.
South facing gardens.
Note: The windows in the houses above have almost certainly been
replaced with 1950s metal casements.
RDSAP Manual March 2012
1930s
Metal casement windows came into fashion in the 1930s and have
much to do with the recognisable look of many houses from the
1930s. Typical features of the 1930s:
Bay windows with horizontal banding
The cavity brick wall, which was enshrined in the 1936 Model
Bye Laws, came into more common use around this time
Introduction of the hipped roof–expansive roofs with short
ridges and tall chimneys
Ribbon developments–suburbia as we know it began to grow
along the approach roads of our towns and cities
The car is accommodated on the plot, usually in a separate
garage
Building styles were influenced by developments on the continent,
particularly by the Bauhaus (the influential German school of
architecture).
The ‗between wars semi‘ is another classic house type of this period.
Features that typify the ‗between wars semi‘:
Formal entrance with the half round opening to the porch
area, front door is set back slightly.
Decorative glazing in door panels.
Roof extends forward over the bay window, with decorative
timber or brick above the glazing.
The densities have increased from the luxuries of the garden city
houses of the 1920s; this is particularly so in the private sector house
of this period. More examples of 1930s dwellings are shown in the
following photos.
RDSAP Manual March 2012
Above: Examples of 1930s houses.
1940s
During the Second World War, house building came to a virtual halt
except for the prefabricated dwellings. Many of these developments
are still lived in today, many years after their design life expectancy
of around 20 years.
Immediately after the World War II there was a rush to fill the
housing shortage with system built housing estates. There are dozens
of different types of system built houses, too many to cover here, but
it is fairly easy to research those where you live with the help of local
information from the library or the council.
To identify a 1940s house, look for:
System built walls–concrete panels, although many of the
houses will have been re-clad in brick with new windows
RDSAP Manual March 2012
fitted under housing defects legislation. These should be
entered as ‗system built‘ in wall construction.
Corrugated roofing systems.
Steel frames, often visible in the roof space.
The houses depicted above are ‗Woolaway‘ houses.
1950s
The 1950s saw the beginning of a major boom in housing
developments, with mass production of building materials producing
a standardisation across the country. Typical 1950s houses features:
Festival of Britain (1951) influences in the flat roofed porches
supported on metal posts.
Plain brick walls (from the mass production of London bricks).
Metal casement windows.
Concrete roof tiles.
Bungalows became popular during the 1950s.
Open-plan estates where properties were less clearly
separated from neighbours by clear boundaries e.g. no walled
front gardens.
1960s
RDSAP Manual March 2012
Houses in the 1960s:
The chalet or dormer bungalow (notice the rooms in the
roof).
Integral parking provision (a feature of the late 1950s and
1960s).
The kitchen/diner and open plan living room is often a feature
of this period.
Flats in the 1960s:
In the public sector the 1960s saw major developments of
flats in blocks of three or more storeys.
The tall tower block is often from this time period.
1970s
During the 1970s there was a positive reaction against the sameness
of the 1960s. Signs of the 1970s:
Developments of two and three storey houses–a conscious
attempt to create not only a variety in the built form but also
a mix of house types catering for a varied population.
Increase in housing density created by the rise in land prices.
Reaction against the ‗open-plan‘ estate, with the enclosure of
private space by high walls and fences.
Greater attention given to external detailing.
Off plot parking and carports are a feature of this period.
Dominance of gas central heating results in a lack of
chimneys, and increasing number of ridge vents.
Large windows reflect the use of double-glazing and the use
of Velux roof lights can be seen.
The Essex Design Guide (a planning guide produced by Essex County
Council) was influential in promoting cluster housing, breaking up the
fronting and reducing road widths.
RDSAP Manual March 2012
1980s
1980s estates are also characterised by high densities. But there was
a move back to a more conventional estate layout.
Cul-de-sacs with tightly packed houses are a common
feature.
There is a conscious move to use different house types to
give variety.
The large windows reflect the common use of double-glazing
but there is often a nostalgic attempt to soften the effect with
curved window heads and imitation leaded lights.
The chimney creeps back again particularly on the larger
house type: but more as a result of the gas flame effect fire
than any desire to revert to solid fuel heating.
1991–1995and1996–
2002
There is little difference in style between 1991–1995 and 1996–2002
but for relatively new homes like the one shown above it is more
likely that the actual date of construction will be known.
Houses are closely packed, often in large volume estates. House
builders may use a number of subtly different house types to create
variety. There is also a conscious effort to break up box-like outlines
with a mixture of popular features from the past, often jumbled
together: bay windows, pillars, porches, decorative brickwork,
cladding or tiles to parts of elevations are commonly seen.
The detached (sometimes only just) house is the most common built
RDSAP Manual March 2012
form on many estates. Post-1990 houses will also have:
Extractor fans (or sometimes passive vents in recent
properties) in kitchen and bathroom(s).
Trickle vents to windows.
Allocated parking, driveways or garage (often two garage
spaces for larger houses).
Roof timbers may exhibit a date of manufacture in large
painted letters.
Electricity installations may be dated as may be hot water
cylinders or gas meters.
Take care not to rely on windows for dating; they are often changed.
post-2002
For almost brand new homes it is likely that the actual date of
construction can be found. However, there are visible differences
between post-2002 housing and estates built in the 1990s, due to the
influence of central government planning guidance (the John Prescott
rules). These asked for higher densities in an effort to reduce the
impact of new build housing, and encouraged the redevelopment of
brown field land instead of green field development.
Thus many post-2002 estates are redevelopments of inner city
former light industrial areas. Houses are closely packed, often
including three storey terraces and low rise apartment blocks.
RDSAP Manual March 2012
Conversion date
When dating a property, in some instances the conversion date
rather than the original build date of the property should be used.
However, it should only be used if you have documentary evidence of
the date of the conversion.
The conversion date will be more appropriate as conversions have to
comply with Building Regulations and therefore their thermal
performances will be improved. This does not apply to
refurbishments, only conversions such as:
Barns/mills converted to dwellings;
Warehouses converted to dwellings;
Houses converted to flats.
In addition, if a property has been completely refurbished, choose
the age band in which the building control approval was granted.
Completely refurbished means walls, floors, windows and roofs. If a
property has only been partly refurbished, the original build date
should be used.
If you are able to establish in advance of the inspection that the
property is a conversion, you can request documentation from the
owner and reasonably expect to get it. Design your pre-inspection
questionnaire or telephone question list carefully.
RDSAP Manual March 2012
Roof rooms
For RDSAP rooms in the roof can take several forms:
A house designed for occupation of the roof space such as a
chalet bungalow, usually built with dormer or roof light
windows.
A conversion of what would normally be a loft space, above
the main part of the dwelling, or above any extensions.
Above left: Modern room in roof construction with ‗Velux‘ or rooflight
window.
Above right: dormer windows suggest rooms in the roof in this chalet style
house.
A: basic roof room
B: roof room with vaulted ceiling
C: roof room with dormer windows
D: roof room with large dormer windows (chalet-style)
For a roof room be included in the RDSAP assessment it must be
accessed via a fixed staircase. For fixed access to be described as a
staircase it must be accessible and traversable in both directions by
an able-bodied person moving in a forwards direction.
Loft conversions accessed by a fixed ladder rather than a staircase
and require that you exit the room backwards in order to negotiate
the ladder do not qualify as roof rooms and should be treated as loft
spaces. A roof room does not need to contain any habitable rooms.
For a roof room to be classed as such and not a separate storey, the
height of the common wall must be less than 1.8m for at least 50%
of the common wall (excluding gable ends and party walls)
If the common wall is 1.8m of greater the room in the roof should be
RDSAP Manual March 2012
recorded as a separate storey.
A ‗common‘ wall is a vertical extension of the external wall of the
storey below. Don‘t confuse this term with ‗party‘ wall.
Diagram A
Diagram B
Diagram C
Diagram A: Loft conversions are often constructed with stud
partition walls that provide a vertical wall in the eaves, a space that
would not be useful to the room. These stud walls lose heat into the
void behind them, a space which is referred to as the residual roof
space. Diagram A has a residual roof space to either side of the stud
partitions which can often be accessed by hatches or small doors. In
Diagram A the residual roof space is assessed as the main roof for
the property and does not belong to the roof room. The height of the
common walls in Diagram A is zero and the diagram clearly
represents a roof room.
Diagram B: The height of the common wall is denoted by the
arrows. As it is less than 1.8 m this means that this diagram
represents a roof room for RDSAP. There is no residual roof space
Diagram C: The height of the common wall in Diagram C is greater
than 1.8 m and this means that this would be an ordinary storey
rather than a roof room. An area weighted ceiling height would need
to be calculated.
RDSAP Manual March 2012
Roof room or
ordinary storey–
refer to flowchart
Where you identify the presence of roof rooms, details of this storey
are entered in the ‗room in roof‘ section and not as a normal storey.
Remember that you should enter the floor area as either an
additional storey or as a room in the roof, gbut not both. Therefore the
chalet-style house on the previous pae is recorded as a single storey
dwelling PLUS a roof room.
If you are certain that you are looking at a roof room (and extended
measurements are not required – see later in this chapter) then you
only need to measure the floor area internally. There is no need to
measure a heat loss perimeter as the walls of the roof room are
considered part of the roof. . The floor to ceiling height is also not
required although it is good practice to make a simple elevation
drawing as part of your site notes, to create a record of the situation
you found.
RDSAP Manual March 2012
Is roof room
adjoining?
If the roof room is connected to another roof room (in the same
dwelling) or connected to another part of the dwelling then the ‗is
roof room adjoining‟ should be ticked. This will reduce the assumed
area of heat loss through the walls of the roof room.
Note: a roof room within a terrace of houses, where the
neighbouring house appears to have a roof room, is not considered
adjoining. It must be adjoining part of the same dwelling.
Roof room
insulation
Roof room insulation can be tricky to assess. The diagram below
shows the possible locations of insulation. It may be possible to
access the void above the flat ceiling (marked in blue) and the
residual void either side of stud partitions (marked in yellow and
entered as the residual main roof, rather than as part of the roof
room). In these locations you would typically expect to find a layer of
mineral wool fibre insulation. But it may be more difficult to assess
insulation that lines the sloping part of the roof (marked in orange),
the stud walls (marked in green) and the gable end (marked in grey).
Access to these areas may be severely limited and it may be that you
will have to rely on documentary evidence if a visual inspection is
impossible.
Parts of a roof room
The insulation depth levels set in RDSAP are for mineral wool type
insulation that usually comes in rolls. Where you encounter expanded
polystyrene insulation board or multi foil insulation the convention is
that you should double the thickness of the board so that its better
performance is more accurately reflected.
RDSAP Manual March 2012
Polystyrene insulation board and multi-foil insulation
You may encounter other insulation types as insulation is a rapidly
developing area. You can check with NES technical support if
uncertain of how to record it.
The screenshot above shows the section of the software that deals
with rooms in the roof. Information is needed on the main roof room
(and up to four other roof rooms, if there are extensions present).
The floor area is required and is measured internally. The age range
of the roof room is required; this might be the original date of build
of the house or the conversion date if you are able to reliably
establish it.
Important Note: the residual roof spaces either side of the roof
room are not considered below–they are part of the MAIN ROOF and
NOT part of the roof room. The insulation assessment for the residual
roof is recorded on the Age and roofs‘ page.
RDSAP Manual March 2012
The residual roof space is effectively the remainder of what was the
main roof after the roof room was constructed.
The possible insulation entries are as follows:
Unknown–this entry will mean that the software will use the
default level of insulation for the year you have entered for
the roof room. Pre-1966 this is likely to mean no insulation.
No insulation–this is self-explanatory and means the software
will consider the roof room entirely un-insulated. There may
still be insulation at joists level in the residual roof space.
Flat ceiling only– this is when there is insulation present
above the flat ceiling and nowhere else. There may not be a
flat ceiling at all in cases where the ceiling is ‗vaulted‘.
All elements comprises of the gable ends, stud walls and
sloping ceiling (orange, grey and green in the parts of a roof
room diagram).
There are 4 options for ‗All elements‘:
o All elements 50 mm
o All elements 100 mm
o All elements 150 mm
o All elements unknown–this is different to simply
‗unknown‘. It means that you can see insulation is
present, believed to extend to all elements, but you
are unable to sure of thickness.
When entering insulation as all elements you will need to also
enter the thickness at flat ceiling separately. If the roof room
has a vaulted ceiling, select ‗not applicable‘ for the thickness
at flat ceiling.
RDSAP Manual March 2012
Extended data
RDSAP calculates the area of the flat ceiling, slope, stud and gable
walls based upon the floor area that has been entered. In most cases
this approximation provides a good model of the heat loss of
characteristics of the roof room. In situations where there is
documentary evidence of the U-values of the slope/stud/gable AND
those U-values differ, detailed measurements should be taken.
There are four measurements required as well as the floor area:
1. Area of the flat ceiling
2. Area of all stud walls: include all vertical (non-gable) parts of
the roof room
3. Area of all sloping part
4. Area of the gable end(s)
If you know the U-values of the slope/stud and gable AND they are
the same, you can enter the U-value in the extended data and use
the RDSAP default areas (see below).
Where detailed measurements are being made and the floor area of
the parts of the dormer protruding beyond the line of the roof is less
than 20% of the floor area of the roof room, measure the elements of
the roof room as if the dormers were not there. If the floor area of
the protruding parts of the roof room is 20% or more, total all the
vertical elements of the dormers in that building part and enter as
stud wall. Any flat ceiling parts of a measured dormer should be
entered as flat ceiling.
In most cases you will find that the dormer windows cover
significantly less than 20% of the roof room area. This convention
was introduced to make sure that large dormer windows in chalet
bungalows (see photo) are included when measuring.
RDSAP Manual March 2012
Above: Chalet bungalow with large dormer windows, the area covered by the
parts of the dormer protruding beyond the line of the roof are greater than
20% of the roof room area.
Above: Roof room with large dormers, but the area (white bounded by green)
is less than 20% of the floor area of the roof room.
Select extended data on the main roof room page to open the extended data
fields.
RDSAP Manual March 2012
The extended roof room data for each building part allows data entry
for two of each roof room element. This has been provided to help
when a very complicated roof room is measured and it may be easier
not to combine all the slopes or stud walls etc.:
Flat ceiling 1 and Flat ceiling 2 are any parts of the roof
room that are horizontal. This could include the flat ceiling
element of a dormer (if they are included). If there are no flat
ceiling parts to the roof room (for example a vaulted ceiling)
enter ―0‖m2.
Stud wall 1 and Stud wall 2 are any parts of the roof room
that are vertical walls added to the roof room, abutting the
roof void. These could include the vertical parts of the any
included dormer. In the unlikely event of there being no stud
walls, enter ―0‖ m2.
Slope 1 and slope 2 are any parts of the roof room that are
sloping. They can be tricky to measure, but you must enter
the area of the slope, not the floor area that the slope covers.
If there are no sloping parts to the roof room enter ―0‖ m2.
Gable wall 1 and Gable wall 2 are the parts of gable end
that form the roof room. You may find that there are no
gable ends, a mid terrace house or stud walls erected to
provide storage in the residual loft. If there is no gable wall
enter ―0‖ m2. If the roof room includes a common wall and a
measured dormer window includes the common wall, enter
the common wall part of the dormer into one of the Gable
wall fields.
RDSAP Manual March 2012
There are three columns containing information about the default
values of the roof room. These are described below:
Column A: these are the default areas for the four elements
of the roof room, calculated from the floor area entered in
the roof room details section. These figures cannot be
overwritten and will remain visible for your reference when
overwritten values in the other columns
Column B: As with column A these are the default areas for
the four elements of the roof room. However, in column B
you are able to overwrite these areas with your own
measurements.
Column C: This column contains the default RDSAP U-values
based on the information about age and insulation entered in
the roof room details section. With documentary evidence
these can be overwritten.
Remember: you will only need to take detailed measurements of a
roof room when: Evidence exists that the U-values of the
slope/stud/gable differ and you know all three U-values.
example: extended
roof room
measurement
In this example there is documentary evidence that the stud and
slope have been insulated to a U-value of 0.30 W/m2K and the gable
ends to 0.25 W/m2K. The flat ceiling can be accessed via a small loft
hatch and has 250mm of rock wool insulation.
floor area of roof room = 3.5 x 7.2 = 25.2 m2
area of flat ceiling = 1.6 x 7.2 = 11.52 m2
area of stud wall = 2 x (7.2 x 1.2) = 17.28 m2
area of slope = 2 x (1.5 x 7.2) = 21.6 m2
RDSAP Manual March 2012
area of gable: The gable end can be a little more complicated to
measure, you will need to divide the area into triangles or trapeziums
and rectangles
In this example divide each gable into a trapezium and a rectangle:
area of rectangle = 1.2 x 3.5 = 4.2 m2
area of trapezium = ½ x 1.15 x (3.5 + 1.6) = 2.93 m2
area of gable = 2 x (4.2 + 2.93) = 14.26 m2
Above: Exampledata entry.
All of the following photos are examples of rooms in the roof for
RDSAP.
Above left: A modern chalet-style house; above right: An early 1900s house with rooms built into the
roof space.
RDSAP Manual March 2012
Above: A modern house built with a roof room.
Dating a roof
room
If a roof room is not a part of the original dwelling or extension, i.e. if
it is a conversion made since the original dwelling was built, then how
do you know how to age it? If the householder is present on an
inspection and they know when the conversion was carried out,
supplemented with documentary evidence, then you should use that
age. Otherwise, as a worst-case scenario, you will have to assume
the age of the dwelling or extension in which it resides.
Flats and roof
rooms
There are three situations you may come across where you have a
flat or maisonette and a roof room. These are illustrated in the
diagram below. The shaded areas represent the parts of the building
that are being assessed.
(A): Flat totally in the roof space. This shows a flat that is located
entirely within the loft space. This flat cannot be entered as a roof
room, as in RDSAP a roof room cannot be entered without a dwelling
below it. In case (A) the flat must be entered as a separate storey, a
top floor flat at floor position 3. The room height for this flat should
be entered as 2.2m.
The floor area should be measured internal and is the area up to any
stud walls. The heat loss perimeter should be measured and the wall
construction assessed.
RDSAP Manual March 2012
The main wall construction should be entered as timber frame, if the
gable ends are of a different construction these should be entered as
an alternative wall. If the ceiling above the roof can be accessed then
the insulation should be measured.
(B): Flat with roof room. For RDSAP this should be entered as a
flat with roof room. The important thing to note with this example is
that it is a top floor flat and the ‗floor position‘ and the fact that it is
only one storey. The floor position in this example is 2.
(C): Maisonette with roof room. As with Diagram B the roof room
is not an extra storey and therefore the dwelling has two storeys and
not three. This is a top floor maisonette with floor position 1.
Roof rooms and
standard rooms
on the same floor
Where there are both ‗standard‘ rooms and ‗rooms in the roof‘ on one
storey, the dwelling should ideally be split between ‗main‘ and
‗extension‘ to separately identify the sections incorporating the
different room types. Remember if a roof room in one building part is
connected to a storey in another building part, the roof room should
be described as ‗adjoining‟ .Where it is not possible to split the
property in such a way, the decision to enter the data as either
‗rooms in the roof‘ or an extra storey is based on the following
criteria.
To enter a complete storey as rooms in the roof, at least half the
storey must be made up of such rooms. Where there are less than
50% roof rooms, the complete storey should simply entered as a
separate storey in the conventional manner. Note that room heights
may need to be ‗averaged‘ and that the inclusion of alternative wall
types may be appropriate to describe different walls within the mixed
roof room/conventional room.
Above: A house where the first storey is part ‗standard rooms‘ and part roof
rooms.
RDSAP Manual March 2012
In the example above the house should be artificially divided into
main and extension along the red dotted line. The main house will be
entered as a 2 storey and the extension as 1 storey with a roof room.
The roof room will be specified as ‗adjoining‘ to account for the nonheat loss wall along between the main first storey and the roof room.
Mansard roof
A Mansard (or Gambol) roof is the top storey of a dwelling that is
built into a lightweight timber framed and tiled structure very similar
to a roof structure but built with near vertical external walls. RDSAP
defines a Mansard as a structure with walls of external slope that are
70 to 90 degrees from the horizontal, rather than the typical 30 to 45
degrees of a ‗normal‘ roof line. A Mansard construction may also have
a low pitch ‗loft space‘ directly above it that may be accessible for loft
insulation assessment.
Where a Mansard roof is identified it should be entered as a separate
storey and NOT as a roof room. It may also necessitate the use of an
alternative wall type in order to differentiate the near-vertical
‗wall‘, which is constructed of a timber frame and tiled, from the
structure of the main dwelling.
Above: A Mansard type roof where the external wall is actually part of the
roof construction.
RDSAP Manual March 2012
Windows
introduction
Windows can be framed in wood, metal or uPVC but for the RDSAP
survey the frame material is not required. However the type of
glazing (single, double or triple glazed) does need to be recorded.
There are three key data items that are needed for windows, i.e. the
total glazed area; the proportion of multiple-glazed area; and the
multiple-glazing type.
u-values and
g values
It is also possible, where presented with reliable documentary
evidence, to enter the U-value and g value of multi-glazing. A g value
is a measure of the total solar transmission, i.e. heat, through a
window and is eexpressed as a number between 0 and 1. The lower a
glazing‘s g value, the less solar heat it transmits. A window‘s g value
is determined by the type of glass, or combination of types, that
make up the glazing unit.
In most domestic situations the specification of glazing concentrates
on admitting solar energy whilst preventing energy from being reradiated from inside.
If entering U-values and g values, and having reliable documentary
evidence, additionally identify whether the g value is a BFRC (British
Fenestration Registration Council) value or otherwise. A BFRC g value
is for the whole window, i.e. the glazing and the frame; other g
values are just for the glazing. If unknown, then assume the g value
is not a BFRC value.
RDSAP Manual March 2012
window area
Total glazed area
normal or typical
When assessing window areas, we include all areas of glazing of the
whole dwelling except for conservatories which are dealt with
separately.
‗Normal or typical‘ applies if the surface area of the glazing in the
dwelling is as would be expected of a typical property of that age,
type, size and character. This applies even if there is slightly more
or less glazing than would be expected (up to 10%).
‗More than typical‘ applies if there is significantly more area of
glazing area than would be expected (15%-30% more), perhaps
because several sets of patio doors have been added.
‗Less than typical‘ applies if there is significantly less glazing than
would be expected. This is rare as homeowners tend not to remove
windows. However, a property may have an unusual design with few
windows.
much more/much
‗Much more than typical‘ and ‗much less than typical’ should be
less than typical
used for dwellings with very unusual amounts of glazing; such as a
glass walled penthouse flat or a garden room or sun room (that
cannot be classed as a conservatory and therefore dealt with
separately). This option allows the measurements of each window to
be input into the software individually. This option can also be used
if a dwelling has a mixture of glazing types, e.g. single, double and
triple glazing and does enable a detailed and accurate entry of the
windows to be made.
Some traditional stone and cob cottages may have less than typical
window openings and older houses may also be found with brickedup window openings leftover from the glass and window taxes of
several hundred years ago.
Each window will need to be measured, the glazing type noted and
the orientation of each window recorded using the eight points of
the compass. The screenshot of the software below illustrates this
and also shows where U- and g values are to be entered.
RDSAP Manual March 2012
It is not normally necessary to measure window area. The software
contains defaults based on the age of the property, and whether it is
a house or flat. These defaults have been obtained by measuring
window areas on several thousand houses of different ages and
represent the best possible approximation. However, if recording an
alternative wall containing window openings, you may have to
measure the windows within the area of the alternative wall.
A glazed door is classed as a window if the glazing totals 60% or
more of its surface area.
Do not include conservatories in your property glazing assessments
as these are dealt with independently elsewhere in the procedure.
Proportion
multiple glazed
This is a simple assessment of the proportion of glazing that is
double or triple glazed. Secondary glazing should be entered as
double-glazing, because properly applied secondary glazing does
decrease the heat loss through glazing. However, temporary
secondary glazing using products such as cling film should not be
counted. Note that the proportion multiple glazed is based on the
window area rather than the number of windows.
Multiple glazing
type
The software presents the following categories:
Pre-2002
Post or during 2002
Unknown install date
Secondary glazed
Triple-glazed
Pre 2002 doubleglazing
The basic assumption for double-glazing pre-2002 in the software is
for typical units that have a 6–12 mm air-gap between the panes. For
identification purposes these will usually be starting to show their
age.
RDSAP Manual March 2012
The 2002 building regulations required replacement double- glazed
Post 2002 doubleunits to reach a minimum standard for heat loss. In order to meet
glazing
this standard, most new double-glazed units now come with a Low-E
coating. This is why the survey asks for the window installation date,
as modern glazing is better than typical older double-glazed units.
If the windows have been retro fitted since 2002, the householder
will most probably be aware, and should also possess a FENSA
certificate (required by Building Control).
Sometimes it is possible to find a date of window build located on the
metal strip around the edge of the sealed glazing unit; although this
is not to be confused with any BS Kitemark dates that might appear
on the panes themselves.
The RDSAP software allows the different types of double-glazing to be
accurately entered, but this makes surprisingly little difference to the
overall result, and does not alter any recommendation that the
software may make to replace the single glazing. The gap between
panes may be up to 20 mm
If you are uncertain whether a double glazing installation was made
before or after 2002, the website of the Fenestration Selfassessment Scheme (FENSA) allows you to search by postcode for
installation dates. Visit their website at: www.fensa.org.uk
Secondary glazing Properly fitted secondary glazing should be counted as a type of
multiple glazing. Where secondary glazing panels have been
removed, e.g. during the summer in order to fully open windows, but
the frames remain, if the assessor can be provided with suitable
visual evidence that the glazing panels still exist and can be re-fitted,
then the property can still be assessed as having secondary double
glazing.
RDSAP Manual March 2012
Triple-glazing
Triple-glazed windows consist of three panes of glass with two air
gaps. They are quite rare and likely to be slightly thicker than
double-glazing. If you come across double-glazing with the addition
of secondary glazing (often found in houses next to busy roads), this
should be entered as post 2002 (post 2003 in Scotland and post
2006 in Northern Ireland) double-glazing.
single-glazing
Single-glazed units lose heat more rapidly than double- or tripleglazing and tend to be draughtier. However, because multiple-glazed
units can be expensive, it is common for ‗multiple-glazed‘ properties
to still have some single-glazing, particularly in rooms where less
time is spent, e.g. downstairs toilets, porches or store rooms. Since
2002, Building Regulations have prevented the installation of
replacement single-glazing in most cases.
Extended glazing
and sunrooms
The RDSAP definition of a conservatory is that it is a structure with
at least 75% its roof and at least 50% of its walls glazed; and of
course to include the conservatory in RDSAP it must be nonseparated (i.e., not separated by external quality doors).
Sometimes you will come across a structure that has 75% + of the
roof glazed (or polycarbonate) but not 50% of the walls glazed, or
vice versa (often referred to in estate agent details as ‗sunrooms‘).
In these cases you should make use of the extended glazing facility
in NES one. The example below shows you how to enter the
‗sunroom‘ details as an extension with extended glazing.
The sunroom in question is little more than a lean-to. It has three
solid brick walls with small windows but a totally clear polycarbonate
roof. In the illustration below, the blue highlighted area shows the
clear roof and two small windows.
The way to treat this ‗sunroom‘ is to enter it as an extension and use
the extended glazing facility. This will enable you to put in the roof
as a ‗rooflight‘. If the glazing in the rest of the property is ‗typical‘
there is no need to measure all the windows; use the windows area
RDSAP Manual March 2012
table to calculate an assumed area for the main property and enter
this as 1 window.
To show you what should be entered in the software lets assume
that the roof in this case is 8.2 m2 and the two single glazed
windows in the sunroom are 0.50 m2 each. The total floor area of the
1967 house with pre 2002 double glazing is 78 m2.
Assumed window area: (0.1239 x 78) + 7.332 = 17.0 m2
Doors and high
performance
doors
The DEA must record the total number of external doors which
includes doors to unheated corridors and any doors within the heat
loss perimeter:
Ignore doors to heated corridors
Include doors to separated conservatories, unheated
garages, stores, etc.
Identify the number of insulated doors: this can only be done
with documentary evidence
Record the U-value of the insulated doors: again
documentary evidence is required with this option
With more than one type of insulated door, record the
average U-value of the doors
RDSAP Manual March 2012
Draughtproofing RDSAP requires the DEA to assess, identify and collect the number of
windows and doors that are draught proofed:
The proportion of draught proofed windows and doors is
entered as a percentage (%) and then allows a more
accurate recommendation for draught proofing to be made.
The following conventions apply:
All external doors and at least two windows must be
assessed.
If a window is locked or inaccessible endeavour to try
another one.
If the condition of the draughtproofing cannot be determine
then assume multi-glazed units to be draught-proofed and
single glazed units not to be.
Lighting
Portable lamps
The energy assessor must record:
The total number of light fittings in the property (counted in
accordance with the conventions outlined below).
The number of low energy lighting fixed outlets in the
property (counted in accordance with the conventions
outlined below).
Lamps that are plugged in and therefore portable are ignored.
A quick lighting
reference
Following is a quick reference to the common types of lighting.
nonIncandescent or general light
low
service lamps—25-100 watts.
energy
non–
Tungsten halogen lamp–these can
low
be 12 volts or 240 volts, but neither
energy
is low energy. Low voltage does not
RDSAP Manual March 2012
mean low energy. They are often
used as recessed spot-lights.
low
energy Fluorescent tubes–common in
garages and occasionally in
kitchens.
low
energy Compact fluorescent lamps (CFL) 315 watts approx.
low
energ
y
low
energ
y
This CFL is designed to replace
halogen spotlights and on close
inspection the small fluorescent
tube can be seen within.
low
energy This CFL is shaped like a bulb. It
may flicker when switched on.
Light emitting diode (LED). LED
technology is constantly developing.
These can replace halogen
spotlights and down lighters.
what is a low
energy light?
A low energy light outlet is an individually wired lighting outlet that is
either low energy by its inherent design, e.g. fluorescent strip lights,
or a ‗standard‘ outlet that has low energy lamps installed.
Low energy lights are efficient in the sense that more of the wattage
goes towards producing light than with traditional tungsten lighting.
With a traditional non-low energy light, up to 80% of the energy
powering it goes toward generating heat and only 20% to light. Try
placing your hand close to a non-low energy light and feel the heat it
produces.
Further clues to identify low energy lighting:
Low energy lights will often flicker when switched on.
They may not instantly reach full illumination.
They may be seen to flicker when illuminated, if viewed
through your digital camera.
They will not radiate heat to the extent of a non- low energy
light, if you place your hand close to the light.
RDSAP Manual March 2012
RDSAP Manual March 2012
Electricity meters
According to the BBC‘s Watchdog programme, over 6 million
households in the UK have dual rate meters, which are used for offpeak electricity tariffs such as Economy 7, Economy 10 and Economy
White Meter (Scotland only). The electricity is switched to the
cheaper off-peak rate for use with electric storage heating systems
and water heating with electric immersion. Cheaper electricity is
available during the night when nationally less is being used.
Remember that for the RDSAP assessment we are trying to establish
the electricity rate ‗regime‘ that applies to the property being
inspected. That is, is the system currently working on a single or a
dual rate? It is possible to find dual rate meters that are capable of
operating dual rate but that are currently set only at single rate. In
this case we would say that the meter is a single rate meter.
single rate meters Single rate electricity is charged at the same rate regardless of the
time of day used.
Left: single electricity meter.
Dual rate meters Dual rate meters were first introduced in 1969 to create a steadier,
round-the-clock electricity demand and lessen the burden on the
network at peak times. Dual meters are cost effective when at least
20-25% of the electricity is consumed at off-peak rate.
Timers attached to the heating and water heating systems turn those
systems on in the night when electricity is charged at a cheaper rate.
Electricity customers on a dual rate do usually pay slightly more for
their day-time (or on-peak) electricity.
RDSAP Manual March 2012
24 -hour
electricity tariff
The 24-hour electricity tariff applies only to modern slim line storage
heaters, combi storage heaters and fan assisted storage heaters.
These types of electrical heaters lose their charge of heat by the
evening and therefore are considered by many to be ineffective. To
counter this problem some electricity supply companies have allowed
some customers to obtain cheaper than peak rate electricity to
recharge their storage heaters. This system may be difficult for the
DEA to identify without talking to the homeowner and even looking
at the electricity bill. The metering arrangement may not provide all
the information needed but the presence of a tele-switch may be a
clue as remote control by the electricity company is usually a
feature.
Mechanical dual
rate meters
Left: tele-switch
When identifying a dual rate meter, it is necessary to establish that
there are two rates. On the mechanical electricity meter shown
below, two rows of figure dials can be seen: ‗Normal‘ and ‗Low‘. On
some meters these may also be called ‗Day‘ and ‗Night‘, or ‗Rate 1‘
and ‗Rate 2‘.
Above: mechanical dual rate electricity meter.
RDSAP Manual March 2012
Digital dual rate
meters
On a digital dual rate meter an LED display is used to display the
tariff information. There are different types of digital meters;
depending on the model of the meter, the LED information may be
displayed in sequence, or a button may need to be pressed to show
the readings.
Both the on-peak and off-peak units are displayed one after the
other, with a number at the top indicating which rate is currently
being used. For example: ‗1‘ is displayed along with the total number
of units for Rate 1, and then ‗2‘ with the total for Rate 2 (see photo
below).
Above: digital duel rate electricity meter.
other tariffs
A 24-hour tariff is used only with whole-house storage-based
heating systems and is only available in Scotland. The primary and
secondary heating, water heating and electricity for pumps and fans
are all charged at a lower rate. All other electricity use is charged at
the normal rate. The storage heaters are re-charged remotely by the
electricity supplier, so this arrangement can be identified by the
presence of a separate tele-switching device.
Above: tele-switching device.
RDSAP Manual March 2012
storage heaters
with single rate
meter
If the meter has been identified as a single rate meter and there are
storage heaters at the property, this system should be entered as
on-peak electric heating in the software. This models the actual unit
cost more accurately, and will reduce the SAP rating accordingly.
If the meter is not accessible, or if the meter type cannot be
determined, unknown should be entered. For storage heaters and
other off-peak only heating systems entering unknown will enable
the software to assume dual rate.
dual meters that
appear single
Some meters, notably the ‗Ampy meter has only one screen and
shows the tariff information by switching from one reading to the
next every fifteen seconds. You will have to watch it for this length of
time at least to be able to determine whether it is set up for one rate
or two.
Note: On this meter, the ‘Single-phase‘ refers to the 220 volt
electrical distribution system at the property and is unrelated to
single rate. This has been an area of confusion in the past.
Above: dual meter, showing one reading at a time.
meters with a
blue button
Above: these meters allow the user to switch between the various tariffs by
pressing a blue button on the meter.
RDSAP Manual March 2012
smart meters
The UK Government has recently announced plans for every
household to have a smart meter fitted by 2020. Smart meters give
real-time information on electricity usage to allow the householder to
better monitor (and reduce) their electricity consumption.
Above left: Smart meter; source: www.hydroone.com; above right: Smart
meter; source:www.echelon.com.
Open fireplaces–ventilation
This is a straightforward count of the open fireplaces within the
property. The software simply requires the number of open fires to be
entered. However, the energy assessor must understand the
conventions that apply. There are two reasons why open fireplaces
are important in RDSAP:
As a possible heating system; this is dealt with in the section
on heating systems.
As a ventilation system, which is what we are concerned with
in this section.
Anyone who has sat in front of a roaring open fire will know that open
fireplaces and their chimneys strongly affect the ventilation rate of
the house, with a lot of heat escaping up them. Even when unlit the
ventilation continues, which is why you will often encounter measures
to block up or restrict the loss of heat from open fireplaces and their
chimneys, particularly if the fires are never lit.
We need to define what counts as an open fireplace and we are
primarily counting any open fireplace that has an unrestricted flow of
air up it. This would include the following:
Unrestricted open chimneys that have a diameter of over 200
mm, if circular or 30,000 mm2 in cross sectional area.
Open chimneys with a non-flued appliance installed
For example an un-flued gas fire standing in the hearth.
Temporarily closed chimneys where the occupant has taken
RDSAP Manual March 2012
temporary steps to reduce heat loss such as using cardboard
or foam to block the chimney. This could easily be removed.
Do not include in the open fireplace count fireplaces that incorporate:
A chimney less than 200 mm in diameter. This can be difficult
to judge sometimes. Small Victorian fireplaces can be less than
this but if in doubt worse-case would be to record it as open.
A flexible flue liner sealed into the chimney that restricts flow
below the 200 mm diameter.
A fireplace fitted with a damper. This is usually a metal plate
that can be easily opened when the fire is in use or closed
when not.
A chimney for solid fuel appliances with controlled flow of the
air supply below the 200 mm diameter.
A chimney fitted with an open flue gas fire where the flue
outlet is sealed to the chimney. This usually means a plate is
fitted at the base of the chimney (top of the fireplace opening)
which restricts the flow of air below the 200 mm diameter.
A fireplace that contains a flued appliance such as a wood
burning stove or gas fire.
A permanently blocked fireplace perhaps fitted with ventilators
where the fireplace would have been. The ventilators allow
enough ventilation to the chimney to prevent dampness within
it.
A chimney pot with a cap on top that prevents a flow of air and
rain entry.
Above: these caps effectively prevent air flow up the chimney.
RDSAP Manual March 2012
Above: these ventilating chimney pots DO NOT effectively restrict heat loss up
the chimney.
Above: the solid fuel stove fitted to the fireplace means that it is not open for
RDSAP. The stove restricts air flow up the chimney.
Above: a damper which enables the air flow up the chimney to be closed off
when fireplace is not in use. Fitted at base of chimney.
RDSAP Manual March 2012
Self-test:
Do you understand all the key points made in this Section? Test your
knowledge here! If you get stuck then note down your best guess, go and
Section 4
find the answer from the pages of the Section.
Q1 (3 marks)
Examine the photographs of dwellings shown here as A to D, and then
attempt to the following questions:
A
B
C
D
(a) Give one example of a dwelling built prior to 1900 ________
(b) Give one example of a dwelling built in the 1930s ________
(c) Give one example of a dwelling built since 1980 ________
Q2 (1 mark)
Look at the details in this photograph. What age band would you predict
for this property?
RDSAP Manual March 2012
Q3 (2 marks)
From the picture, what is the property type, built form and age of the
dwelling?
Property type ____________________________
Built form _______________________________
Property age _____________________________
Q4 (5 marks)
For the flat bounded in red in the photo below, complete the property
details.
Flat type ________________________
Floor position ____________________
Built form _______________________
Floor heat loss type _______________
Property age _____________________
RDSAP Manual March 2012
Q5 (3 marks)
Examine the photographs of dwellings shown here as A to D, and then
attempt the following questions:
A
C
B
D
(a) Which dwelling has rooms in the roof ________
(b) Which dwelling has an external porch ________
(c) Which dwelling is likely to have an alternative wall type ________
Q6 (1 mark)
In the diagram below what is the length of the heat loss perimeter?
______________________________________________
RDSAP Manual March 2012
Q7 (2 marks)
From the picture shown in Q4, what is the flat type and floor position of
the flat bounded in red:
Flat type ____________________
Floor position_________________
Q8 (5 marks)
(a) Under what circumstance would a conservatory be classed as nonseparated?
_______________________________________________
_______________________________________________
(b) What data is recorded for non-separated conservatories?
_______________________________________________
_______________________________________________
Q9 (1 mark)
A three-bed semi-detached property has the following…
Hall, lounge, kitchen/diner, separate dining room, stairs, landing, three
bedrooms, study, family bathroom and downstairs shower-room.
How many habitable rooms are there?__________________
The answers to this self-test can be found on the next page.
Section 4 Self-test result: ____ / 23
RDSAP Manual March 2012
self-test answers
Q1
A
C
D
Q2
The solid brick walls and fan-light over the window indicate it is likely to be 19001929.
Q3
Property Type........
Q4
House
Built form..............
Detached
Property Age.........
1930-49
Flat type...................
Mid-floor
Floor position............
5
Built form..................
Enclosed end terrace
Floor heat loss type....
Other dwelling below
Property age.............
Q5
1950-1966
A
D
C
Q6
8.3 + 8.3 + 5.7 = 22.3
Remember to include the length of the unheated corridor in the total heat loss
perimeter
Q7
Flat type...................
Top-floor
Floor position............
Q8
3
If it is open to the rest of the dwelling, or it is not separated from the main dwelling
by an ‗external quality‘ door.
The length of the glazed perimeter
The height (number of storeys)
The floor area
Whether it is double glazed
Q9
7 habitable rooms: lounge, kitchen, kitchen/diner, dining rooms, 3 bedrooms, study.
Not habitable rooms: hall, stairs and landing, bathroom and shower room.
Section 4: Score:_____ / 23
RDSAP Manual March 2012
5. Section five | Construction
Wall construction types
introduction
The first section of Section Five deals with wall construction in sufficient
depth to provide the new entrant to energy assessment with the
necessary basic knowledge. Further reading on the subject is
recommended and a good reference book is Marshall and Worthing, The
Construction of Houses (provided with your training material).
In this Section of the training manual we concentrate on what is required
for the energy assessment of standard UK housing stock, specifically the
entries for walls that are required for the RDSAP software.
There are wall types (used mainly regionally) that are not covered here.
For example, bungeroosh of Brighton, clay batt of East Anglia and
others. If you encounter these you can use the EPC addenda to help
explain this in the EPC.
Getting the wall type right is essential. Consider for a moment the
implications of getting such a fundamental element wrong. Your choice
of wall type appears in the EPC report and anyone reading it, on noting
your error, will have reason to doubt your competence and the accuracy
of the EPC report in its entirety.
RDSAP wall
types
The software uses the wall type that you enter along with the property
age and insulation to assign a suitable rate of heat loss to the wall. The
DEA is required to correctly identify the wall type(s) at the property,
including any insulation and enter the wall(s) in one of the following
RDSAP wall categories:
Cavity
Solid brick
Timber framed
System built
Sandstone
Granite or whinstone
Cob
RDSAP Manual March 2012
These wall types are listed broadly by how common they are. With some
regional variation, cavity walls are the most commonly encountered,
generally built from the 1930s to the present day. Next are solid brick
walls, used in most of the Victorian housing stock. At the bottom of the
list is cob which many DEAs will never encounter unless they live in a
few specific locations, mainly in the south-west.
The NHER survey form prompts you to record certain information about
walls. Wall identification can be difficult and the information we provide
here will help identification in most cases. Because walls can be
plastered internally, sometimes rendered externally and generally do not
allow you to see within their structure, it pays to take time and care to
make an informed decision on the wall type, reflecting on all the
evidence and not relying on the first clue that presents itself to you. Use
more than one piece of evidence for the wall type; consider the
following:
Measure the reveal (the wall thickness)
Look at the brick bond
Observe the inner surface of the wall in the roof space where
you may be able to see the bond
Are there drill holes from insulation works?
What is the age of the property?
Is there insulation? Retro-fit or from new?
Consider what the software will assume about the walls given
the age; remember that your knowledge of the RDSAP age
bands tells you that the software assumes no insulation for walls
pre-1966, fully filled cavities from 1983 and so on. (See Section
Four.)
Are there gaps around pipes or vents that might actually allow
you to view within the wall using your torch?
Any wall type may be found to have an external outer layer, e.g. a
render (sand and cement/lime) coating, vertical tile hung elevations,
stone tile facing, weatherboarding. These do not generally alter the basic
wall type. For example a cavity wall which is tile hung is still a cavity
wall. Each wall type is will be considered in the following pages.
RDSAP Manual March 2012
Remember your site notes: record how you identified the wall and its
insulation so that anyone reading your notes can verify your wall
identification.
wall identification tips
cavity walls
The cavity wall was originally designed to reduce water penetration and,
although used earlier, became the norm in the UK in the 1930s,
replacing the solid brick wall. The cavity wall consists of two skins of
brick or block work, with a gap in between, i.e. the cavity.
The outer and inner skins will be joined by wall ties, which connect them
and keep them parallel. A useful by-product of the cavity was that it
trapped air (air being a poor conductor of heat and therefore an
insulator) and so was thermally better performing than solid brick
walls—even without added insulation.
From the outside, a brick outer skin will look like this (image below).
Note the absence of ‗header‘ bricks, only the sides of the bricks are
visible.
Above: Examples of cavity wall construction.
RDSAP Manual March 2012
Above: Cavity wall with insulation.
Above: A cavity wall could have an outer skin of reconstituted stone blocks. This
is still a cavity wall; note the drill hole for retro-fitted insulation.
RDSAP Manual March 2012
Above: Section through a typical 9‘ solid brick wall.
Above: Examples of solid brick walls.
Timber framed
walls
Timber framed properties have been around for hundreds of years and it
is helpful here to consider them in two separate categories: the old and
the newer types.
Traditional
timber frame
The photo below shows a traditional thatched timber framed house,
clearly pre-1900. The panels between the timbers can be rendered
wattle and daub (or lathe and plaster), sometimes replaced by brick.
Above: The walls of this property should be entered as timber framed in the
RDSAP age bracket pre-1900 and the software will apply the appropriate heat loss
values for the walls.
RDSAP Manual March 2012
Above: Infill panels replaced with brick.
Modern timber
frame
Modern timber framed properties often appear outwardly to be very
similar to cavity walled houses and will require a close inspection
internally.
The basic assumption for modern timber framed walls is that they are
constructed of an inner wooden frame which supports the load of the
building. The frame contains or is adjacent to the insulation. There may
be a cavity which allows air to circulate around the timbers. The outer
layer of the wall is generally of a single layer of bricks.
Timber frame dwellings, built during the 1960s, typically used two
methods of insulating the frame: either a 25 mm quilt stapled to the
frame or a bitumen impregnated fibreboard on the outside with a foilbacked plasterboard on the inside. The former gives a slightly lower rate
of heat loss.
Above: Traditional or modern timber framed houses can also be weather-boarded
over the timber frame.
RDSAP Manual March 2012
In the mid-1970s timber frame housing was at its peak with a slice of
the housing market of up to 25%. The 1970s constructions used 60 mm
of insulation quilt.
Since the early 1980s, 80 mm or 90 mm of insulation has become the
norm. Right up until the 2001 Building Regulation changes, this
construction performed better than was required by legislation, outperforming standard cavity constructions houses.
Above: A partly built timber frame house by Potton Ltd. This property has a block
outer skin, which will be rendered (apart from the stone edging and window
surrounds).
Above: A section through a typical timber frame wall showing the outer brick
skin, internal plasterboard and vapour barriers. Total wall thickness is similar to
cavity wall constructions.
RDSAP Manual March 2012
How to identify
timber frame
A systematic approach to inspection will enable the DEA to identify
timber framed wall construction but DON‘T rely on any one clue. Make a
decision based on the following:
Externally there may be open perpends in the brickwork. Although these
may also be present on a cavity wall, crucially on a timber framed wall
these will be found at eaves level and are designed to ventilate the
wooden frame.
Tapping the interior plastered wall surface in a number of places
should produce a hollow sound. You are tapping on plasterboard
mounted to timber studs so this will sound different to the solid
sensation of tapping on a cavity wall.
Note: beware the hollow sound that may be heard if a cavity
wall has a plaster boarded inner surface mounted on wooden
battens or plaster dabs. This may sound confusingly similar.
Look in the loft space and the inside of the triangular gable walls
of the wooden frame will be seen; these may possibly be
covered in a sheathing board material.
If the house is connected to another house, plasterboard may be
visible as a firebreak separation between loft spaces. In a cavity
built house these triangular gables would probably be brick or
block.
Look for access points that may enable you to see inside the wall
structure. These could include meter cupboards, telecoms
hatches and vents.
Some timber framed houses will be built with the windows set in line
with the wooden frame thus appearing to be slightly recessed in the
wall. This is unreliable in many cases where windows may have been
replaced.–Ask the owner–this is the kind of thing they may well know.
Left: View of gable end from within roof space–
note the mineral fibre batts protruding up into the
roof space, and the sheathing is also visible
between the studs.
RDSAP Manual March 2012
System built
houses
System-built refers to many different non-traditional construction
methods, such as prefabricated concrete panel construction or steel
framed housing. Many of these were built in the years after World War II
in a bid to make up for lost years of house building. Timber frame is not
classed as system-built but is entered as a separate wall type.
The software tries to attach a suitable rate of heat loss to the majority of
non-standard constructions. The date built is the most influential factor
when selecting this wall type. Many of these homes were or still are in
local authority ownership so it may be possible to obtain accurate
information on date.
For the age bands prior to 1967 an assumption is made that
system-build construction did not perform particularly well thermally.
Many of the 1960s tower blocks would also be classed as system built;
they were often of concrete, steel and glass construction.
Even some modern homes fall into the system built category if their
construction does not fall into one of the other wall type brackets. If
these are recently built, their walls will have been required under the
building regulations to perform as well as other walls.
It is impossible to consider all the hundreds of types of system-built
homes here but there are publications available to help with
identification of specific types. All that is required of the DEA is that he
or she determines simply that the walls are system built, their insulation
and the date.
There are many types of system-built walls that have been successfully
insulated, mainly by local authorities or housing associations. Again, the
subject is too large to cover here but the DEA needs to establish through
discussion with the owner and through a visual inspection if the walls
have been insulated internally, externally or within a cavity if one exists.
stone walls
Stone is a very common building material found in a wide range of
properties from the vernacular rural cottage to the grand townhouses of
cities like Bath and Edinburgh. The stone would often be locally quarried
and in its traditional form it is rarely used today for new house building.
RDSAP Manual March 2012
Above left & middle: Examples of stone wall construction; above right: Bath town house.
The software assumes that stone walls are thicker than other
constructions (500 mm). For the purpose of RDSAP, stone walls are
divided into two very broad categories to reflect their different thermal
properties:
Granite/ Whinstone
Sandstone
Granite/
whinstone
Above: Examples of granite wall construction.
Granite is a very hard, igneous (volcanic) stone which is found across
the UK but is notably more common in Scotland, Devon and Cornwall. It
can be recognised by its very hard, coarse texture and often crystalline
appearance, and local knowledge of your own area will help. RDSAP
assumes that un-insulated granite walls lose heat more rapidly than do
sandstone walls.
Whinstone is a term used to describe a group of very hard dark stone
types quarried for building use.
RDSAP Manual March 2012
Sandstone
Above: Examples of sandstone wall construction.
The sandstone wall category represents most of the stone houses in the
UK including the limestone used for many of our grand city buildings and
much of the rubble stone walling that forms the more ordinary
vernacular housing in many areas; it is often rendered.
Sandstone is softer to the touch and being of a sedimentary origin may
be visual layered in its structural appearance. Its porous structure is
generally greater, trapping air and therefore improving slightly on
granite‘s poor thermal performance.
Cob walls
Cob walls are primarily found in just a few geographical areas of the
country, most notably the south-west. Local knowledge is invaluable in
understanding any peculiar wall type in your area because identification
in some cases can be difficult without it.
Cob walls are constructed of unfired earth mixed with rubble and straw
formed into a homogenous mass wall structure, built up in layers on top
of a stone or brick plinth wall base. Cob is almost always rendered which
can conceal the wall and give the appearance of a stone wall.
Desk research, local knowledge and talking to the owners may help
identification. Visually the corners of the house may be rounded off,
thatched roofs are common and the walls may in some cases have an
uneven look.
It is possible to find other wall structures involving unfired clay such as
the clay batts of East Anglia but those are more likely to perform like
solid brick walls and lack the thickness of a cob walls. An un-insulated
cob wall performs better thermally than either of the stone wall types.
RDSAP Manual March 2012
Above left: a cob wall with the render partly removed, above right: a traditional cob cottage.
Wall insulation
introduction
See the following section in this Section for the wall insulation entries
that you need to make to the software. For the purpose of RDSAP, wall
insulation takes three forms:
Cavity wall insulation
Internal wall insulation
External wall insulation
In rare cases, it might be possible to have a combination of these types
of insulation. For example: cavity filled walls plus an external wall
insulation.
Cavity wall
insulation
Cavity wall insulation may have been installed within the wall when it
was originally built or it may have been retro-fitted later.
In recent years a cavity wall built with insulation would probably contain
an expanded polystyrene board within the cavity. This will probably be
impossible to see and you will be relying on the date of the building to
enable the software to apply the correct default U-value for the wall.
Left: A cavity wall with insulation.
RDSAP Manual March 2012
RDSAP makes the assumption that all walls built after 1983 contain this
type of insulation and makes no further recommendation to add more
insulation to the cavity. Cavity walls built before 1983 are assumed to
have empty cavities and are able to be retro-filled with insulation in
most cases. Before 1983 some improved thermal values may have been
achieved by the use of thermal blocks. These assumptions are fairly
general and in reality it is entirely possible to find cavity walls built after
1983 that have empty cavities and could be retro-filled. This is a
limitation in the RDSAP methodology.
Modern cavity fill techniques usually use 10-20 mm holes drilled into the
mortar joints between the bricks following a specific drill pattern. The
insulation usually takes the form of blown fibre or expanded polystyrene
beads, injected through the holes under pressure to completely fill the
cavity. The specific drill pattern is used to ensure the complete filling of
the cavity with insulation. The holes are then filled with a matching
mortar and in many cases fairly close inspection is needed to spot the
holes.
Retro-fitted
cavity wall
insulation
Evidence of a cavity wall having been filled could include the following:
Identifying drill hole patterns.
Asking the householder: if the work has been carried out in
the last few years they will probably have a Guarantee
certificate from C.I.G.A.
Peering through any openings in the wall, internally or
externally, such as air-bricks, vents, extractors, cracks,
damaged mortar, meter cupboards, etc.
where the insulation (expanding foam in
particular) can be seen escaping from the cavity in several
possible locations including the top of the walls in the eaves
and either at the top of or between the joints of the blocks in
the gable end wall, where the pointing is poor.
If there is tile-hanging on the external wall, this will prevent drilling for
insulation and in these cases you will need to check the corresponding
wall surface inside the house for drill holes. Your torch, shone across the
wall, will reveal concealed drill holes after decorating.
RDSAP Manual March 2012
RDSAP Manual March 2012
Health and safety rules now prevent in some cases the installation of
cavity wall insulation in first floor walls above garages and
conservatories. The installer may have drilled from inside the house.
If there is an area of wall that has not been insulated owing to a lack of
access for the installer then this must be consider a possible area of
alternative wall. This means all walls must be checked for insulation–don
not rely on just a few drill holes.
There are other means of injecting cavity walls that are under
development and different methods have been used in the past,
including removing whole bricks. The DEA should be aware of advances
in technology and other techniques.
Don‘t rely on just one piece of evidence. Always corroborate your
findings with other evidence. You might think that drill holes would be
conclusive evidence of a cavity wall but installers have been known to
insulate timber framed and system built walls.
Above: Drilling a hole in the mortar and inspecting the cavity.
Above: The first place to check for drill holes (usually 2-3 brick courses
below the windows).
RDSAP Manual March 2012
Internal
insulation
Internal insulation is most often applied to solid brick walls as a retro-fit
improvement measure but may also be found on stone walls, system
built, and very occasionally on a cavity wall. It usually takes the form of
a standard plasterboard panel backed by expanded polystyrene
insulation board, as in the photo below.
The plasterboard and insulation may be mounted on wooden battens and
the whole combination may be between 50 mm-100 mm thickness. This
will reduce the room size slightly and because the plasterboard may then
be decorated over; it may be difficult to detect the insulation.
Installing can be awkward around existing room features, so a close
inspection may reveal places where you can actually see the insulation,
such as in cupboards. Internal insulation on solid walls can be detected
by tapping gently on the internal surface. There is a noticeable
difference in sound between plasterboard on a soft insulation and other
surfaces. This form of insulation will mean that the room will heat up
quickly as there is no need to use energy to heat the mass of the walls.
Remember that when measuring polystyrene or polyurethane insulation
board the convention is to double the measured thickness, to give a rock
wool equivalent.
Dry-lining
Beware the term ‗dry-lining‘ which is a commonly misunderstood term.
Dry lining is a plaster boarding system that does not require wet plaster
to be applied and it does not include any insulation. It is simply a
plaster board applied to either wooden battens or dabs of plaster.
RDSAP Manual March 2012
An air gap is created between the wall and the plaster board, improving
the thermal performance of a solid wall by about 25%. An uninsulated
solid brick wall of 225 mm thickness would have its U-value improved
from 2.1W/m2K to 1.55W/m2K.
The presence of dry-lining is determined by tapping the inside face of
the wall in an attempt to locate the more solid ‗dabs‘ among the hollowtapping parts of the wall. 2cm to 4cm of additional wall thickness will be
created by the dry-lining.
Above: installing internal wall insulation.
Left: Traditional Lathe and Plaster is also
classed as a dry lining by virtue of the air
gap that is created behind the plaster.
RDSAP Manual March 2012
External
insulation
Unlike internal insulation, this insulation system is applied to the exterior
of a wall. It is still fairly rare but has seen some increase in popularity
with local authority housing, including some system built. Most
commonly it is seen as a retro-fit improvement measure to solid brick
walls but can also be found on other wall types.
External insulation does not reduce room size and does not cause
internal disruption. It may also provide weather protection to the
external façade of the property and provide an attractive decorative
finish. The system takes advantage of the thermal mass of the wall by
having that mass on the inside of the insulation, heating up and cooling
down slowly and thus maintaining an even internal environment.
Above: schematic diagram of external wall insulation system.
There are various systems of external insulation that have been used
including an aerated insulation-containing render and insulation boards
covered by render. It is not always possible or desirable to alter the
external appearance of a property in such a drastic manner.
Above: External wall insulation being installed–in this photo the final layer
(render) is being applied.
RDSAP Manual March 2012
Above: Social housing on the Cockhill Estate, Birmingham.
Above: the ‗step‘ that suggests external wall insulation.
Render alone does not constitute insulation. You must be certain that
the wall is insulated. As it is a retro-fit measure there may be a step of
up to 100 mm or more near the base of the wall where the insulation
starts.
RDSAP Manual March 2012
Tile hanging
The photo below shows a solid brick walled cottage that has had the first
floor hung with tiles probably to stop penetrating damp. To recap on this
chapter ask yourself:
Q: Is the first floor a solid brick wall too?
A: Probably in this case but in some cases the upper wall might
be timber framed. Further investigation is required and definitely
an internal inspection.
Q: Is the first floor wall alternative?
Answer: Not if it is a solid brick wall. Just because it is tile hung
does not change the fact that it is solid brick.
Q: Is the first floor externally insulated?
A: There is no evidence to suggest this from the photo and it is
highly unlikely. Tiles alone do not constitute insulation.
Above: Solid brick wall with tiles hung on the first floor.
RDSAP Manual March 2012
Data entry
The screenshot above shows the data entry screen for a solid walled
property with two extensions.
Construction type: The Construction type entry asks for the
basic wall type, in this case solid brick.
Insulation type: Depending on the wall construction, the
insulation type could be internal, external, unknown or as built.
In this case it is As built, i.e., it is as constructed. Insulation
thickness (if there is any) is requested next.
Insulation thickness: A drop down list gives a choice of
insulation thicknesses. In the unlikely event of encountering both
internal and external insulation on a wall the convention is to add
the two thicknesses together and enter them as being external.
Wall thickness: This is usually measured in a window or door
opening and is the dimension taken from the internal finished
surface of the wall to the external finished surface. The
requirement to enter the wall thickness has been incorporated for
a number of reasons:
o To improve the calculation that converts external
measurements to internal measurements
o To improve the ground floor U-value calculation
o To help identify narrow cavities
o To calculate a more accurate u-value for stone walls
Wall thicknesses of between 50 mm and 1500 mm can be
entered.
RDSAP Manual March 2012
Unmeasurable: If the wall thickness is unmeasurable the
option to tick the ‗unmeasurable box‘ exists in the software. This
should be a last resort and this option must be accompanied by
evidence, possibly photographic, of why you could not measure
the wall.
Dry-lined: If the wall is dry-lined there is a tick box to check.
This option is only available with stone and solid brick walls. The
impact of dry-lining is less pronounced with the other wall types.
U-value known? If you have reliable documentary evidence
that justifies entering a U-value directly, then this can be done.
RDSAP Manual March 2012
Floor construction types
introduction
The software uses the floor construction and age to calculate the rate of
heat loss through the floor, which can be in the region of 10% of the
total heat loss from the building fabric. A separate floor entry is required
for the main property and any extensions and the floor type will appear
on the EPC report.
The DEA is not expected to lift carpets and it can be difficult therefore to
make a visual inspection of a covered floor. Some skill is required to
correctly identify a floor in some cases.
There is the option in the software to record unknown for the floor type
but this should only be used in extreme cases. By the end of reading this
section on floors and with a little practice you should be able to identify
floor construction in almost all cases. The default approach to recording
floor insulation is to use As-built unless there is evidence of retrofit
insulation having been installed. However, it may be reasonable in some
cases to record unknown for the floor insulation only where there is
conflict between what you can see and documentary evidence you have
been shown. Your visual inspection would usually override anything you
are told by the occupant.
In RDSAP there are three recognised floor types:
Suspended timber
Suspended–not timber
Solid
Construction and identification
Surveyors use a technique known as the ‗drop heel test‘ to help identify
floor construction. It involves raising the heels off the floor, standing on
the toes and then dropping the heels down on to the floor. The surveyor
will observe whether the resultant sound and impact/flex suggests a
hollow or floor structure.
It may be possible to see the top of the floor structure in cupboards,
under the stairs or where carpet is missing.
RDSAP Manual March 2012
Suspended
timber floors
This is a wooden floor suspended over joists above a void. The floor
could be constructed of wooden (or composite wooden) sheets or
traditional floor boards. A suspended timber floor may feel ‗springy‘ and
may creak when walked upon. Outside the property at the base of the
walls there are likely to be ‗air bricks‘ present to aid ventilation which is
important for timber floors.
Above left : A suspended timber floor; above right: An air brick/vent.
Insulation
For RDSAP, a suspended timber floor will be assumed to be insulated
when built, if built after 1996.
Retro-fit insulation is still uncommon because of the difficulty of
installation. It can take the form of mineral wool or insulation board
suspended beneath or between the floor joists or as an insulation board
laid on top of the floor boards.
These are normally suspended concrete floors, also known as beam and
Suspended, not
block floors. The joists are suspended above a void and are usually
timber floors
concrete with concrete blocks inserted between them. There may be a
concrete ‗screed over the top and/or a boarded surface.
They will feel solid underfoot and will often be more even-surfaced or
level than a suspended timber floor. Unlike solid floors there are likely to
be air bricks present, more in common with a suspended timber floor.
Performing the ‗drop heel test‘ in the centre of a room may reveal some
vibration in the floor and possibly the audible sensation of the void
beneath your feet.
Suspended–not timber floors are more likely to contain insulation from
their original construction because they are a more modern system of
flooring. Again 1996 is the key date from which the software will assume
them to be insulated and whether original or retro-fitted, the insulation
will either be beneath, sandwiched within or on top of the floor.
RDSAP Manual March 2012
Solid floors
These are concrete structural floors that have been ‗poured in‘ at the
time of construction, directly on to the substrate without there being any
void. This type of floor will have no air bricks present and will feel solid
underfoot. A drop heel test will reveal no movement and no sound
associated with a void.
Left: A solid floor being broken up.
1996 is again the date from which the software assumes these floors to
be insulated. This insulation may be beneath the concrete surface
‗screed‘ or laid above the floor in board form. If retro-fitted it is most
likely to be above any concrete and therefore may be visible.
Mixed floor
types
It is common to find properties with more than one floor type. This may
also be true for houses built on sloping plots. Many Victorian properties
have a suspended timber floor through most of the dwelling but a solid
floor in the kitchen. In these cases the dwelling should be divided into
main and extension. This enables the different floor types and their
respective levels of insulation to be represented exactly in the software.
Remember that term ‗extension‘ here is used in its RDSAP sense of a
part of the property that is thermally different.
Floor insulation entries
unknown
insulation
If there is conflicting evidence presented and you simply cannot be sure
enough to use the default As-built option.
As with other elements such as roofs and walls, using unknown has the
effect of suppressing any recommendation.
as-built
insulation
As-built should be recorded where the floor insulation has not changed
since the dwelling was constructed. The software will assume levels of
insulation based on the age of the dwelling and the building regulations
of the time.
RDSAP Manual March 2012
Retro-fitted
This is rare and especially difficult to see, given its location, and if
encountered you may have to rely on the owner‘s documentary evidence
for proof of installation. Photographic evidence may be acceptable.
Remember that floor insulation under one part of the house does not
mean that it extends under the whole house. It may be necessary to
split the house into main and extension if the house floor is only partly
insulated.
Where floor insulation is identified, the insulation thicknesses are 50
mm, 100mm, 150 mm and unknown. Unknown will mean an assumption
in the software of 50 mm.
U-values can be entered for floors if reliable documentary evidence is
available. This is simply a matter of ticking the ‗known box‘ and entering
the value.
You do not need to record floor construction and insulation when
inspecting an upper floor flat.
RDSAP Manual March 2012
Roof construction types
introduction
For RDSAP residential roofs are divided into two basic
categories:
Flat roofs
Pitched roofs
Flat roofs
Flat roofs are defined as being roofs which are laid at an angle
of up to 10 degrees from the horizontal. They may be found
above the main dwelling but are more commonly covering
garages and rear extensions. The insulation is likely to be
sandwiched within the layers of the construction of the roof and
therefore inaccessible.
Above: flat roof above extension.
Flat roof insulation
If the flat roof is inaccessible (usually the case) you can record
unknown and the software will base its insulation assumption on
the age of the property (or extension).
If you are able to see or have evidence of a retro-fit installation
of insulation, the software allows you to enter 50 mm,
100 mm, 150 mm or unknown. Unknown in this case will
mean 50 mm is assumed by the software.
RDSAP Manual March 2012
Pitched roofs
Pitched roofs are defined as being laid at an angle of between
10 and 70 degrees from the horizontal. Less than a 10 degree
angle and it becomes a flat roof, more than 70 degrees and the
roof becomes wall. Roof insulation within a pitched roof can
usually be accessed during the energy assessment and will be
found either laid at ceiling joist level or at the rafters.
Above left: examples of
pitched roofs
right: loft insulation at
Above middle: loft insulation Above
rafters
(less
common).
at
joists level
The software uses the roof type description along with the property age
and loft insulation to assign a suitable rate of heat loss to the roof. The
only requirement is to identify a broad description for the roof
construction, and whether the insulation (if present) is located at rafter
or joist level.
Using the software
roof
construction
The options in the software for roof construction are:
Flat
Pitched, access to loft
Pitched, no access to loft
Pitched (thatch)
Other dwelling above
If the roof is pitched but you cannot access it for the inspection, then
select Pitched, no access. If there is another dwelling above the property
you are inspecting, select Other dwelling above.
RDSAP Manual March 2012
Roof insulation There are further options to record the position of any insulation:
Rafters
Joists
Unknown
None
Flat roof insulation
Insulation
thickness
The thickness of the insulation should be entered by selecting the closest
depth from the options available. If the actual thickness falls between
one of the software insulation depths, err toward the worst case option.
Above: Celotex is a brand of expanded polystyrene insulation board and its
thickness should be measured and doubled.
Expanded polystyrene insulation board is a more effective insulator for
any given depth than mineral wool roll. The convention is to double the
thickness of the insulation board to get a mineral wool equivalent
thickness. Foil backing is not considered to be significant and should be
ignored.
Measuring loft
insulation
thickness in
practice
The thickness of loft insulation significantly affects the energy rating
result, therefore this should be carefully measured when inspecting an
accessible loft space with insulation.
Insulation board thickness should be measured and doubled if found.
RDSAP Manual March 2012
Insulation at
rafters
If insulation is at rafters it is likely to be of an expanded polystyrene
type and may well not be accessible for measurement. In this case you
can select unknown and the software will default to a value appropriate
to the age of the property. If you can measure the rafters insulation–not
forgetting to double any thickness of expanded polystyrene–the options
in the software are 50 mm, 100 mm or 150 mm.
Insulation at
joists
If insulation is at joist level and is the common mineral wool type you
should measure where possible. Assess as best you can whether that
depth is consistent over the whole of the loft area. If it is, you will simply
need to enter that depth–or the closest of the options available in the
software.
If the insulation is inconsistently laid, partially missing or heaped up, you
will have to judge an average depth and enter that.
If the insulation is boarded over or otherwise obscured (perhaps by
stored possessions) to the extent that you cannot see 50% or more of
the insulation, then you can legitimately enter that the insulation is
unknown. This will result in the software defaulting to the level of
insulation that the age of the property would suggest it would have been
built with.
The following table shows the loft insulation depths and U-values in the
various age bands. These are what the software will use if you do not
specify a depth. The table is just for guidance, but note that it assumes
NO insulation in the roofs of all properties pre-1966.
RDSAP Manual March 2012
Age band
RDSAP assumed
thickness1 (at joists)
K: 2007 Onwards
250 mm
U-value
0.16
J: 2003-2006
250 mm
0.16
I: 1996-2002
150 mm
0.262
H: 1991-1995
150 mm
0.29
G: 1983-1990
100 mm
0.40
F: 1976-1982
50 mm
0.68
E: 1967-1975
12 mm
1.5
A, B, C, D: until 1966
0 mm
2.3
Be careful using unknown: firstly, if you can see there is insulation
present and the property is pre-1966, the software will assume there is
NO insulation present; secondly, any recommendation for further
insulation will be suppressed.
There are a number of other less common insulation materials in use
and the number of these is likely to grow. Sheep‘s wool and hemp
matting are two examples. If you encounter anything you cannot
identify, measure and photograph and seek advise.
Thatched roofs Thatched roofs should be entered as pitched (thatch) and any additional
insulation at joists should be recorded. For thatched roofs there will not
be any loft insulation recommendations, therefore if there is no access to
the loft space simply record unknown.
RDSAP Manual March 2012
To recap, study the following two tables:
Roof construction
type
Pitched, loft
access
A pitched roof (slates or tiles etc) where the loft is accessible. A loft that
is boarded or only a head and shoulders inspection is possible due to
boxes around the loft hatch is still accessible.
Pitched, no loft
access
A pitched roof where there is no loft access, this could be no loft hatch,
or an obstruction such that building work would be required to access the
loft. Recording no loft access will prevent erroneous loft insulation
recommendations.
Pitched (thatch)
A pitched roof that is thatched. Note that the current convention for
adding half the thickness of the thatch to the insulation thickness at joists
no longer applies. Additional insulation at joists can be recorded, but
there will be no recommendations for insulation.
Flat
A flat roof.
Another dwelling This is only an option for a flat or maisonette where the floor position and
above
floors in block do NOT denote a top floor flat.
Roof insulation
None
The loft space can be accessed but there is no insulation at either joists or
rafters.
At joists
The loft space can be accessed and the insulation is at joist level. The
thickness of the insulation should be recorded.
At rafters
There is evidence of insulation at rafters, either visually or documentary.
Flat roof insulation Where there has been retro-fit flat roof insulation.
Unknown
This should be used where the insulation cannot be determined. A boarded
loft for example.
RDSAP Manual March 2012
U-values for roofs can be entered where reliable documentary evidence
is available. See screenshot below.
If you feel comfortable with what you have learnt in this Section, then
have a go at the following Self-test Questions and move on to the next
Section.
RDSAP Manual March 2012
self-test:
Section 5
Do you understand all the key points made in this Section? Test your
knowledge here! If you get stuck then note down your best guess, go
and find the answer from the pages of the Section.
Q1 (1 mark)
Look at the pictures, what is the wall construction?
Q2 (5 marks)
Read the following statements and decide if they are true or false…
(a) In general terms, a 1930 solid brick wall has a higher rate of
heat loss than 1930 cavity construction. True/False
(b) Recording roof construction of flats is not necessary. True/False
(c) Insulation thickness should be recorded where there is internal
wall insulation. True/False
(d) ‗Low-e‘ is a coating applied to glass that reduces heat loss
through glazed units. True/False
(e) A house with a tile hung wall should be recorded as externally
insulated. True/False
Q3 (2 marks)
What indicators could be used to recognise a suspended wooden floor?
_____________________________________________________
RDSAP Manual March 2012
Q4 (4 marks)
When would you measure and record an insulation thickness? Answer
true or false to the following questions.
(a) The thickness at joists of any residual loft space, where there is
a room in the roof created by converting the loft space, and
more than 50% of the residual loft space is accessible.
True/false
(b) A room in the roof with documentary evidence of retro-fit
insulation of all elements with a vaulted (cathedral-style) ceiling
True/false
(c) A room in the roof where the flat ceiling is accessible and there
is mineral wool insulation laid at joist level. True/false
(d) A flat roofed extension, with documentary evidence of retro-fit
insulation. True/false
Q5 (2 marks)
Name two places that you could look for evidence of a filled cavity…
1. ________________________________________________________
2. ________________________________________________________
Q6 (2 marks)
What 2 wall types can be assessed as having dry-lining?
1. ________________________________________________________
2. ________________________________________________________
The answers to this self-test can be found on the next page
Section 5 Self-test result: ____ / 16
RDSAP Manual March 2012
self test answers
Q1
Q2
Solid brick
(a) True
(b) False - Roof construction is necessary when the flat is on the top floor. If flat
is not on top floor record ―other dwelling above‖.
(c) True – if it cannot be measured or there is no documentary evidence of the
insulation thickness, record thickness ‗unknown‘.
(d) True
(e) False – unless there is evidence that there is additional insulation, tile hanging
itself is not considered insulation.
Q3
Q4
Air bricks; The floor will be springy underfoot.
(a) True – record insulation thickness in the residual loft space if at least 50% of
the residual loft space is accessible. This is recorded in the roof construction
section.
(b) False – insulation thickness is not applicable for vaulted ceilings. N/A should
be selected for ‗thickness at flat ceiling‘
(c) True – if the flat ceiling above a roof room can be accessed and there is
measureable insulation at joist level this should be recorded.
(d) True - if it cannot be measured or there is no documentary evidence of the
insulation thickness, record thickness ‗unknown‘.
Q5
You should have two correct answers from this list:
Air bricks
Look in the loft – foam or fibre between the skins of brick cavity walls
Meter boxes
Ask the householder if they have documents or guarantee certificates
Pattern of cavity fill drill holes in a cavity wall
Q6
1. Stone walls
2. Solid brick walls
Section 5: Score: ____ / 16
RDSAP Manual March 2012
6. Section six | Space heating
Main and secondary heating
introduction
The topic of heating is one which can cause some confusion when
assessing a property for energy efficiency. There are more errors made
by DEAs in recording the heating correctly than in any other area of
RDSAP.
Take your time working through this Section. You only need to know the
basics and are not expected to understand the complexity of the
systems as a heating engineer would. We start by looking at what the
software requires from you before moving on to look at the range of
heating systems you may encounter.
The heating system and controls have a major impact on the RDSAP
rating and care is needed to ensure that it is correctly identified.
The DEA is required to enter the heating systems that are present in the
property accurately and according to the conventions as described in
this section of the manual. In principle any DEA inspecting any property
should record the heating systems in the same way and arrive at the
same result.
Main and
secondary
Confusion can arise when there is more than one heating system in the
property. The software allows two main heating systems and one
secondary heating system to be entered.
Main heating
1 and 2
The software allows the entry of up to two main heating systems (if two
are present).
Usually the selection of the main heating system is straightforward and
one system is clearly the primary heating system. For example, in a
house with a boiler and radiator system and a focal point fire in the
lounge, it is the boiler and radiators that is the main heating system and
the focal point fire is the secondary system. The focal point fire would
not be classed as main heating 2 as it only supplements the boiler and
radiators when required.
It is generally the case that there will just be one main heating system.
RDSAP Manual March 2012
There is an option to input two main systems to cover the situation of
Conventions for
different systems heating different parts of a dwelling.
two main
heating systems If main system 1 heats all habitable rooms, there is no main system 2
unless it serves DHW only.
Main systems 1 and 2 cannot be room heaters except in the case of the
dwelling‘s heating consisting solely of room heaters.
A main heating system is generally one that would be described as
central heating (i.e., a heat generator providing heat to several rooms
via a heat distribution system); however, the term does also include for
example storage heaters and fixed direct-acting heaters in each room.
When there are two main hating systems, system 1 always heats the
living area and:
Where two systems serve different spaces, the percentage
recorded for each system is in proportion to the heated floor
area served by each system.
Where two systems serve the same heating circuit the default
assumption should be a 50/50 split. A different ratio can only be
used if there is clear documentary evidence to back this up.
When there are two main heating systems and a recommendation is
made for heating system upgrade, include addendum 9.
A second main heating system is not to be confused with a secondary
heater. The latter is a room heater heating an individual room, either as
a supplement to the main heating system in the room (e.g. a wood
burning stove in the main room) or for a room not heated by the main
heating system(s). See Section Five for rules on secondary heaters.
If there is more than one main heating system within a room, select one
of them according to the rules in SAP Appendix A and disregard the
other.
Integrated storage/direct acting in living area, normal storage heating
elsewhere: treat as two main heating systems.
However, if in a large house, you encountered two boilers serving
Example 1:
two main
radiators in different parts of the house, entering two main heating
heating systems
systems enables you to accurately model the combination of heating
systems using the software. If the two systems serve different parts of
the property estimate the proportion (as a percentage to the nearest
10%) of floor area served by each system.
RDSAP Manual March 2012
In this specific example, if the two boilers serve roughly the same floor
area you would apportion 50% to each boiler.
If in this same example the two boilers served the SAME set of
radiators then the proportion would also be 50% main 1 and 50% main
2.
Another example of this: a three-storey house, each storey is 45 m2, a
gas boiler provides heat to radiators on the ground floor and there are
Example 2:
two main
storage heaters on the two upper floors. The % main 1=33% gas boiler
heating systems
heating and % main 2=66% storage heating.
The percentage does not determine which system is which; rather main
heating 1 should be the system that heats the living room (zone 1).
RDSAP Manual March 2012
Example 3:
separate boiler
for DHW
Sometimes there is a separate boiler providing domestic hot water
(DHW) only. A generic boiler can be selected from the water heating
options. If the boiler is located in the database, specify two main
heating systems with:
Main system 1 is the one providing space heating
Main system 2 is the DHW boiler
Percentage of main heat from system 2 is zero
Water heating is from main system 2
Additional notes
to help with
heating
Some general rules that apply to heating:
Bear in mind that storage heaters may not be found in all rooms
because they work by ‗drift heat‘ around the property.
Storage heaters cannot be recorded as a secondary heating
system–only main.
A boiler and radiator heating system cannot be recorded as a
secondary heating system–only main.
Open fires in upstairs rooms are ignored completely when
identifying the heating systems (it is assumed that these are
historic feature fireplaces and will not be used). The exception
to this rule being reverse level houses with the bedrooms
downstairs. Any open fireplace may still be considered open for
ventilation purposes.
If boiler/heating system is present but not working (or
condemned) it should still be entered as the main heating
system
If boiler not present but intended–enter no heating system.
Open fires that remain potentially operational downstairs are still
potentially heating systems. It is not how the present owners use them
that matters, but the fact that they are there.
RDSAP Manual March 2012
Secondary
heating
Secondary heating is a term used to describe additional room heaters
that supplement the main heating system(s). It is important that any
fixed secondary heating system should be entered even if you think the
main heating is sufficient to adequately heat the property on its own.
However, only one secondary heating system can be entered into the
software, so the conventions described below will show you how to deal
with there being more than one secondary system in a property.
The following are some common secondary heating systems:
Traditional open fires.
Gas or electric focal point fires fitted to the fireplace.
Electrical fans in bathrooms.
Heated towel rails or bathroom heaters.
Electrical radiant heaters in bathrooms.
Kitchen plinth heaters.
We will look at these in more detail later but what these have in
common is that they are rarely used as a main heating system. RDSAP
will attribute (in most cases) ten percent of the heat supplied to the
secondary system.
Remember: central heating systems and storage heater systems
cannot be described as secondary heating.
More than one
secondary
system
You may come across dwellings where you have to select from one or
more secondary heating systems. Under these circumstances you
should make your selection on the following basis:
Could the system be counted as main heating 2 rather than
secondary
If not, select that which heats the greatest number of rooms.
Or if the heated room count is the same:
Select that which uses the cheapest fuel.
Rroom heater can only be main heating 2 if main heating 1 is also
room heaters.
RDSAP Manual March 2012
Portable heating Portable heaters are generally ignored. By portable we mean a heater
that is free standing and can be picked up and carried away. If
electrical, it will be plugged into a socket and if gas fuelled, it will have
its own bottled fuel. If a portable heater is mounted on the wall, fitted
to the fireplace or hard-wired, it is no longer portable and must be
considered for RDSAP.
Inadequate
heating
If there are any habitable rooms that are not heated by either the
primary or the secondary heating, then the dwelling is said to be
inadequately heated.
The software asks you to enter the number of habitable rooms AND
the number of heated habitable rooms. If there are unheated
habitable rooms, the software will make the following amendments to
the calculation:
If less than ¾ of the habitable rooms are unheated and no
secondary heating system has already been identified, then the
software will assume portable electric heaters as secondary
heating for the purpose of the calculation.
Note: the software will do this automatically behind the scenes
and the assessor does nothing.
If ¾ or more (but not all) of the habitable rooms are unheated,
no secondary heating system has already been identified and
the main heater type identified is a room heater. Tthe software
will assume portable electric heaters for the main heating and
the room heater entered as the main heating will be used as the
secondary for the purpose of the calculation.
Note: the heating should be entered as it is observed; the
above procedure happens behind the scenes.
RDSAP Manual March 2012
Main heating systems
central heating
introduction
The two most common main heating systems encountered in UK homes
are the boiler and radiator central heating system and the electrical
storage heater system. There are many different systems that are
capable of providing heating. Here the term central heating is used to
describe systems that are generally capable of heating the whole
dwelling. All central heating systems should be entered in the software
as main heating system.
Storage heating is technically not considered as a central heating
system and they are covered separately later in this Section.
Boiler
The typical central heating system consists of a central boiler and a
circuit of pipe work distributing hot water to a number of radiators. A
hot water cylinder can also be fed off the same circuit. There are several
types of central heating boiler with widely differing efficiencies, so it is
important to correctly identify the boiler type. This is covered in detail
under the heading Boiler Type later in this Section. All boilers are
entered by selecting heater type as Boiler.
Above: The essential components of a boiler and radiator system.
Emitters/
radiators
Most commonly these are radiators, but sometimes a boiler provides
heat via an under floor system. Radiators are situated in strategic
locations throughout the house and are sized by the installing engineer
for optimum performance.
RDSAP Manual March 2012
Under floor
heating
There are two main types of under floor heating systems.
‗Wet‘ under floor heating connected to the central heating
Electrical under floor heating–considered later in this Section.
With regard to ‗wet‘ under floor heating systems, the under floor
element runs off the rest of the heating system (normally a boiler), so
will consist of a circuit of small bore pipes that carry hot water from the
boiler beneath the floor.
Inspection note: on inspection these may be tricky to identify but
visual clues could include the presence of a boiler and plumbing, but no
evidence of radiators.
The under floor circuit may extend beneath the entire floor of a
property, or where there has been an extension built, it may be just
beneath the newer part. With houses, you can find a combined system
with under floor heating to the ground floor and radiators upstairs. If
there is one boiler providing heat to both the radiators and the
underfloor circuit, enter radiators as the emitter. If there are two boilers
(one for underfloor and one for radiators) then this can be split into
main heating 1 and main heating 2.
Above: A wet under floor heating system during installation.
‗Wet‘ under floor systems only require the boiler to heat the water to
around 50°C. As there is a low circulation temperature this optimises
the efficiency of a condensing boiler. By comparison, a boiler and
radiator system would contain much hotter water–around 70-80°C,
which requires burning more fuel. The heating of the air in the room is
also more even without so called ‗cold spots‘.
RDSAP Manual March 2012
Electric boilers
Electric direct acting boilers are becoming more common and a typical
electric direct
acting boilers
example is shown below. They are vastly smaller and slimmer than dry
core boiler units. The direct acting boiler (also called electric flow
boilers) can solely use on peak electricity. If there is a dual meter,
RDSAP assumes that some of the heating requirement uses off-peak
electricity. However, the off-peak fraction will only be 10-30 percent
depending on the tariff and therefore it cannot be compared to a
storage system. The direct acting boiler will normally be a tall thin white
unit, about 1 m tall and 0.1 m square. Although it can be a wall hung,
more rectangular unit.
The system can provide hot water as well as heating, if used in
conjunction with an indirect cylinder. The controls for these boilers have
the same options as gas boilers. To enter this boiler into NES one,
choose heater type: boiler, boiler: standard, fuel: electricity and
system: direct acting.
.
The electric core boiler contains bricks that are heated overnight on off
Electric dry core
peak rate (in the same way as storage heaters–explored later in this
boilers
Section). A fan blows hot air from the bricks onto an air-to-water heat
exchanger to provide hot water for the space and water heating. The
boiler requires a dual meter (Economy 7 electricity).
Smaller units suitable for flats or small houses are similar in size to an
under counter fridge or freezer; larger units are the same size as an
upright fridge-freezer. All units are free standing. They were particularly
popular in the 1970s but are now very rare. To enter a dry core boiler
into NES one, choose heater type: boiler, boiler: standard, fuel:
electricity and system: dry core in heated space.
RDSAP Manual March 2012
Above: An under-counter electric Above: Water storage boiler.
drycore boiler.
Water storage
boiler
The water storage boiler is similar to the dry core boiler in that it heats
up using off-peak electricity overnight.
However, rather than thermal bricks, the heat energy is stored in water.
The units are quite large as they incorporate the water store. The main
difference between this and an electric CPSU (combined primary
storage unit discussed below) is that it uses only off-peak electricity and
the domestic hot water is provided directly from the water store. The
CPSU provides water via a heat exchanger within the thermal store.
To enter this boiler into NES one, choose heater type: boiler, boiler:
standard, fuel: electricity and system: water storage in heated space.
electric CPSU
The electric combined primary storage unit differs from its gas
counterpart by the fact that the thermal store for the electric CPSU
must be a minimum of 270 litres (for gas this minimum is 70 litres–this
will be explained in more detail later in this Section).
It uses a dual tariff and the majority of the heating is done at the offpeak rate. The electric CPSU works by using electricity to heat a store
of water that is then piped to the radiators. The hot water is provided
indirectly via a heat exchanger within the store.
In contrast to the small and narrow design of the direct acting boiler,
the electric CPSU will typically be around 1.8 m tall and 0.6 m as it
encompasses a minimum 270 litre thermal store. The units are often
housed in a cupboard. The controls for this system have the same
Above: Electric
CPSU housed in a option as the gas CPSU.
cupboard.
To enter an electric CPSU into NES one, choose heater type: boiler,
boiler: CPSU, fuel: electricity and system: electric CPSU in heated
space.
RDSAP Manual March 2012
warm-air
Warm-air systems produce hot air, which is then distributed around the
property by a combination of ducting and natural air movement. The
systems are generally large, e.g. occupying most of a full height airing
cupboard, and can also provide water heating via a heat exchanger.
They can be fuelled by gas, oil or off peak electricity.
Some systems are fully ducted, from the heat generating equipment to
every room in the house. Others are stub-ducted, where the main unit
is placed quite centrally in the property and a limited number of short
ducts run to the living areas downstairs.
There will often be vents at high level, allowing the warm air to be
returned to the main heater for reheating. These return grilles are not
normally found in wet areas.
Warm air heaters are entered by selecting heater type as Warm air.
Above: Warm air unit and vents that can be seen in walls and ceilings of a
dwelling.
Heat pumps
Heat pumps work by absorbing heat energy from a low-temperature
source and upgrading it to a higher temperature so that it can be used
for heating. There are a number of heat pump techniques to achieve
this. The ratio of heat energy released to the energy consumed (this is
known as the co-efficient of performance or SPF) is always greater than
one–equivalent to an efficiency of more than 100%.
Heat pump systems are slowly becoming more common. Heat pumps
can either be wet systems which feed radiators/underfloor heating or
warm air systems.
RDSAP Manual March 2012
Air source heat
pumps and
ground source
heat pumps
Heat pump systems operate most efficiently when the source
temperature is as high as possible and the heat distribution
temperature is as low as possible. So heat pumps are categorised by
the low-temperature heat source used (e.g. air, water, ground), with
different default efficiencies for each, ranging from 250% to 320%. A
heat pump is more efficient when supplying an underfloor circuit rather
than radiators as a lower flow temperature is required.
Where occupants have installed air conditioning/comfort cooling and
the system is reversible in order to provide heating, this system would
normally be entered as an air-to-air heat pump fuelled by on-peak
electricity.
Heat pumps are entered by selecting heater type as either Heat pump–
wet system or Heat pump–warm air.
Heat pumps can be selected from the product database or if it cannot
be located in the product database by selecting a default system.
Most heat pumps are limited as to the water temperature that they can
provide. Heat pumps that are used to provide domestic hot water often
have an electric immersion heater to deliver hot water over and above
what the heat pump can deliver.
For a default system, RDSAP assumes that when a heat pump provides
the hot water as well as space heating, 50% of the domestic hot water
is delivered by the immersion heater. If the heat pump is selected from
the product database and the product requires an immersion to top up
the water heating, this information will be contained within the product
data and the DHW efficiency reduced if applicable.
To select a heat pump from the product database, you must know the
Heat pumps
make and model (as with a boiler). If the heat pump cannot be located
from the product
in the product database, a default system must be entered.
database
For each heat pump in the product database there are three entries,
one for radiators, one for underfloor heating and one for fan-coil units.
You must choose the correct system and emitter to enable the correct
efficiencies to be retrieved.
RDSAP Manual March 2012
You may find that when you select a heat pump from the product
database you do not get a result and the error message states:
―Error calculating Appendix N: The plant size ratio is too big”.
The plant size ratio is calculated from the size of the heat pump
and the heat loss characteristics of the dwelling. A heat pump
must be correctly sized for a dwelling to work efficiently. If the
plant size ratio is too big, this means the heat pump is oversized
for the property (i.e. a small well insulated flat with a high
output heat pump.) Conversely, a heat pump with a small output
in a large poorly insulated dwelling may be undersized and cause
a calculation error.
If, when selecting a heat pump from the product database, you get a
plant size ratio error, you should use a default system instead.
RDSAP Manual March 2012
Community heating
Community heating schemes, also known as district heating schemes,
are defined by heat being produced in a boiler house or boiler room in a
block of flats (centralised unit), serving a number of dwellings and
communal areas.
old large volume Old style storage heaters are the large volume, deep units (around 9‘
or 23 cm deep) and dark brown in colour, typically installed in the
1960s. They contain a large quantity of bricks with a high thermal mass
to store the heat. They are normally free standing/floor standing rather
than being wall mounted because they are so heavy.
Left: Old style storage heater.
RDSAP Manual March 2012
Modern slimline
Modern heaters are all the slim-line models. They are usually a
cream or beige colour and are not as deep as the older units. They
contain different bricks for storing the heat, which are smaller and
perform better. This means that the heaters are normally secured to
the wall but will still have small floor supports.
Left: Modern slim-line storage heater.
Fan-assisted
Fan assisted heaters incorporate the use of a fan to control and
extract more heat from the appliance and the fan(s) may be linked
to room thermostat control. Fan assisted storage heaters can derive
more heat from the storage heater by blowing air over it, however,
RDSAP still requires a secondary heating system to be specified, or
assumed by the software is none is present.
They can be easily identified because they will have two electric
input cables, one to charge the storage part of the heater, and one
to power fan motor. The fan may be visible if you shine a torch
through the grills and of course it may be heard rotating.
Above: Fan-assisted storage heater with 2 power cables visible.
RDSAP Manual March 2012
Combi-storage
heaters
A combined (combi) storage heater is a modern slim line storage
heater with an un-fanned convector panel bolted to the front of it. If
required, the occupant can switch on the convector panel to gain an
additional boost of heat. The controls are manual and in effect the
appliance is exactly the same as a storage heater and a convector
panel heater that are not attached to each other. It is just
convenience that has caused the design.
These are visually similar to integrated or fanned storage heaters
but shining a torch down through the grills on top will reveal the
simple heating elements of the convector panel.
These are entered to the software as a storage heater with a panel
heater as secondary.
Integrated
storage/direct
acting heaters
These units are more sophisticated versions of the combined units
and incorporate automatic on-peak top-up as and when required.
Consequently they are more responsive but include a higher fraction
of on-peak energy and can be more expensive to run and more
expensive to install than conventional storage heaters. Examples of
this heater type would be the Dimplex DuoHeat and Creda
EcoResponse units.
Electric underfloor heating
introduction
These are based on elements installed under the floor which cannot
be seen and often provide partial heating only. They can run on offpeak or on-peak electricity.
off-peak only
This system uses the floor as a storage facility for the heat in the
same way that storage heaters use bricks. They will usually have
numbered dial on a wall (usually in the lounge), which is usually not
marked with temperature. This heating system requires a dual tariff
and should have a secondary heating system.
on-peak only
This system uses embedded cables quite close to the surface of the
floor and can use solely on-peak electricity.
RDSAP Manual March 2012
Integrated
storage/direct
acting electric
underfloor heating
Room heaters
introduction
In these cases, the heating will consist of embedded electric cables
that can be used with on and off-peak tariffs. It may be a tariff
arrangement, or may include two sets or areas of cables with one
offering a storage component by heating the floor slab and the other
being located nearer the floor surface to offer a top-up facility.
Many identical room heaters placed around a property may provide
all the heating required. This means that room heaters would be
entered as the main heating system. A mixture of different room
heaters could also be entered, with the type serving the living room
(zone 1) being recorded as main heating 1 and the main heating
2 and secondary heating allocated based on proportion of floor
area served. However, with more and more dwellings being fitted
with some form of central heating or storage heating, the room
heaters in this section will be commonly seen as secondary heating
systems, e.g., a boiler and radiator system with a gas flame effect
open fire in the lounge.
Depending on the main system specified, secondary heating systems
provide for up to 10-15% of the total heating demand.
Gas fires
How do you know if a room heater is a gas appliance? One way to
spot a gas fire is to identify the gas supply pipe going into the
appliance, check along the skirting. Another way is to check that the
flames are real, imitation flame effects are used in electric
appliances. There will also be an ignition and control for the level of
flame. These are usually located beneath a cover at the base of the
fire.
Gas fires, like gas boilers, can have different types of flue, and can
be classed as convector or radiant heaters.
Pure gas convector heaters use an internal gas flame to heat air,
which is then pushed out into the room. Convector heaters tend to
have a balanced flue and have no visible flame, but the gas supply
pipe should be visible.
RDSAP Manual March 2012
Radiant heaters have visible flames or glowing elements, which we
feel heat from. They are more easily identified because they look
more like the typical gas fires we are all familiar with. There are
different types of radiant gas fires, and the efficiency of these
appliances can vary with age, style, and flue type. This leads to
more options in the software.
More modern gas fires use a heat exchanger of one form or another
to capture more of the heat from the flames and transfer it into the
room. The heat exchanger could be ceramic grids, coals, wood
effect, or even stones in new appliances.
.
Old gas fires did not have this heat exchanger; they burnt more fuel
because more flame was needed to directly feel the heat. These
units are now rare, and even quite old appliances often fit the
description of modern gas fire.
Condensing gas fires work on the condensing boiler principle, and
require an additional drain or collection tray to deal with the
condensate generated. These fires have a high efficiency but are
also extremely rare.
RDSAP Manual March 2012
The section on secondary heating later in this Section has more
detail on gas room heater types and how they should be entered as
part of the RDSAP data set for either main or secondary heating
systems.
Open fires
Open fires are exactly that: open fires which burn on a grate or
hearth within an open fireplace. They are usually set into the
chimney breast and burn solid fuel.
Left: A solid fuel open fire.
Unless the property is located within a smoke control area, the
RDSAP convention is to record dual fuel for open fires. That means
mineral and wood. In a smoke control area the fuel type should be
recorded as smokeless fuel. This applies unless you have evidence
the fire is designed to burn only a specific fuel type.
Other than open fireplaces in bedrooms, if an open fireplace is
present and is capable of supporting an open fire, it should be
included in the heating assessment, regardless of whether it is in
use.
Important note: don‘t forget that an open fireplace is not the same
as an OPEN chimney. The latter relates to ventilation (see later in
this Section).
RDSAP Manual March 2012
closed fires
(stoves)
Closed fires are enclosed units, with a door on the front. They might
be set into the chimney or can be freestanding in a room, attached
to an open flue. These fires can often burn a variety of solid fuels.
Left: A solid fuel closed fire.
These might be referred to as log burning stoves or something
similar. If there is evidence that it can only burn one type of fuel,
record this as the fuel type. If it can burn more than one type of
fuel, or there is no evidence as to the fuel it is designed for, then
record the fuel type as wood logs unless in a smokeless zone, in
which case record anthracite. Some HETAS approved wood burners
can be used in smokeless fuel zones and further research will be
required to establish if this is the case.
All room heater systems are entered by selecting heater type as
Room heaters.
Other heating systems
ceiling heating
As the name suggests this system provides heating to the room by a
circuit similar to electric under floor heating, except it is mounted at
ceiling level. This type of heating is recorded by selecting the
heating type electric ceiling heating.
These heating systems can be uncomfortable to live with. In simple
terms, the human body requires warm feet and a cool head, and
with ceiling heating the opposite can be achieved.
Above: Electric ceiling heating during installation.
RDSAP Manual March 2012
Heating fuels
mains gas
Is mains gas
available?
This is the normal gas supply that is piped in from a connection
point in the street. It is one of the cheapest and one of the cleanest
fuels (it emits a low amount of CO2). However, the gas network still
does not cover all towns and villages in the UK, so many properties
will not be able to use this fuel supply.
As part of the RDSAP process, there is a requirement to identify
whether mains gas is available. If mains gas is available and the
property does not have mains gas heating, the software will
investigate the benefits of switching the heating to mains gas and
make recommendations appropriately. Mains gas is assumed to be
available in the dwelling only if:
A mains gas meter is present at the dwelling, or
A mains gas appliance is present in the dwelling (the meter
may be inaccessible).
Note: The fact that mains gas is present in the street is not
sufficient to record that mains gas is available. Use of the above
criteria is to avoid making recommendations that may prove to be
prohibitively expensive when investigated.
LPG
This stands for Liquid Petroleum Gas, which is stored in small metal
cylinders or a larger metal tank in the grounds of the property. A
separate entry is required for each type, either:
Bottled gas
LPG
LPG special condition 18
LPG special condition 18 is specific to four towns: Colden, Llanfyllin,
Llanwrtyd, Stornoway where there is an independent LPG network
charged at the same rate as mains gas.
It is unlikely that houses using LPG have access to the gas network,
as the fuel can be quite expensive, even when bulk buying for the
larger size tanks. The tanks may be concealed underground.
If you discover that the property you are assessing has LPG as the
primary fuel, it may be worth pre-warning the owner that the SAP
rating may be low due to the unit cost of LPG which can be as much
RDSAP Manual March 2012
as double that of mains supplied gas.
Above left: bottled gas; Above right: LPG storage tank.
Oil
This is another bulk buy heating fuel, typically delivered to rural
homes off the gas network. Large green or black storage tanks of
plastic or metal are usually sited close to the property.
The same comments apply to oil heating as for LPG and you are
unlikely to find oil heating where mains gas is available unless the oil
systems predates the gas supply.
Left: Oil storage tank.
Coal
Coal can be burnt in solid fuel fires or boilers and open or closed
room heaters. Coal fired boilers can be manual feed or auto feed,
where a hopper on top of the boiler slowly feeds the fuel in via a
screw-feed mechanism.
Smokeless
This is a manufactured smokeless fuel and fuel gives off less soot in
its smoke than other solid fuels, and is still permitted in smokeless
zones of the country where the level of soot in the emissions is
limited. You can find out about local smoke control areas from the
local council or from the following website:
www.smokecontrolareas.co.uk
RDSAP Manual March 2012
Anthracite
Anthracite is a naturally occurring smokeless fuel and is a grade of
coal that has high carbon content. This means that the fuel has a
higher calorific content, and burning this fuel provides more heat for
a given volume when compared with standard coal.
Biomass fuels
The afore mentioned solid fuels are all types of mineral solid fuels.
Biomass fuels are solid fuels produced directly from energy crops,
which if managed appropriately in a closed-cycle, can greatly reduce
the net Carbon emissions.
The following biomass fuels are incorporated as options within
RDSAP and should be included if identified on site:
Wood logs
Bulk wood pellets
Dual fuel (mineral and wood)
Wood chips
Dual fuel
Liquid bio-fuels
Appliances are referred to as ‗dual-fuel‘ if they are capable of
burning both mineral fuel and a biomass fuel, e.g. an open
coal/wood log fire.
These fuels are derived from biomass and include:
B30K (a mix of 30% biodiesel from cooking oil and 70%
kerosene Biodiesel from any biomass source* (for appliances
specifically designed to use biodiesel and fuel is verified as
wholly derived from biomass)
Biodiesel from used cooking oil only* (for appliances
specifically designed to use biodiesel and fuel is verified as
wholly derived from used cooking oil)
Rapeseed oil*
Appliances able to use mineral oil or liquid biofuel*
Bioethanol (secondary heating only).
*These fuels are only available for selection via the product
database.
RDSAP Manual March 2012
In addition to the fuels already identified, there are a number of
Community heating
other fuels associated with community heating:
fuels
B30D
Waste combustion or municipal waste incineration
Biomass
Biogas–from sewerage or landfill.
Waste heat from power stations.
Electricity:
standard tariff
/single meter
Electricity:
dual tariff/meter
This is the standard metered domestic supply of electricity found in
homes with a meter showing only one reading, referred to as ‗single
rate‘ and charged at the same rate throughout the day and night.
A dual-rate tariff offers an off-peak rate and an on-peak rate.
Electricity is described as off-peak when it is charged at a lower rate.
The meter records the electricity used during a set off-peak period
(usually seven hours at night, which is where the term Economy 7
comes from). Off-peak periods are periods of low demand on
national electricity grid so are charged at lower rates than the
standard domestic supply, and this feature is typically taken
advantage of by electric storage heating systems. During the day
the electricity is charged at the on-peak rate which tends to be
higher than the standard tariff. As well as Economy 7, there is also a
10-hour tariff where there are three off-peak heating periods during
each 24-hour period. If you select a dual electricity meter the
software will select the appropriate dual tariff according to the main
heating system.
Electricity:
24-hour tariff
A 24-hour tariff has been available in Scotland for some time and is
now also available in certain parts of Northern England. The 24-hour
tariff is used for storage based systems, and is only available for
certain storage heaters: modern slim-line and fan assisted.
RDSAP Manual March 2012
Boiler type
introduction
The heating system in a dwelling greatly affects the cost of heating
over a year. A more efficient boiler will burn less fuel to heat the
home to the same temperature. This means that the same levels of
comfort can be achieved more affordably.
The description of the boiler (specified on the survey form) is used
by the software to work out the central heating efficiency.
Sometimes there are clues to the type of boiler you are looking at on
the outside of the boiler casing. In many cases there will also be a
pull down/slide out panel with the manufacturer and model
information written inside. The boiler leaflet, if available, will also
have the information needed. If you can identify the precise make
and model of the boiler on site, you can select it from the Product
Database.
Boiler identification Identifying a boiler from its identification plate:
If marked, a gas boiler can also be uniquely identified by its Gas
Council No. (GC number), when also appearing in the Product
Database.
However, identifying the type of boiler by sight alone is actually
quite simple. A later section explains how to identify the different
types of boiler without having to rely on manufacturer labels. You
should always do this, even if you feel confident that you have
identified the boiler from its label, since it is not always possible to
find the boiler in the Product Database
RDSAP Manual March 2012
Product
database
The Product Database (or PCDF: Product Characteristic Database
File) used to be known as the BEDF or SEDBUK. It contains a list of
gas and oil boilers and has recently been expanded to contain some
micro-CHP, solid fuel boilers and heat pumps.
Clicking on Product Database in the RDSAP software enables you to
search for any of these systems and therefore determine an
accurate efficiency value for an appliance. If you can definitely
identify the installed system in this database, its precise details can
be automatically downloaded into the software without having to
select from drop down menus. This is often the easiest way of
identifying a boiler.
Unless you can guarantee identification of a boiler from the
information available, you will also need to identify the boiler
generically so that you can select the default type from the various
options available in the software. The classification is described later
in this Section.
You should always use the Product Database if possible.
Regular boilers
Regular (also known as standard or conventional) boilers use a hot
water cylinder to store hot water for the taps. They can be identified
as having three pipes (if non-condensing). Regular boilers can have
open, balanced or fan-assisted flues (fan-assisted flues are more
common on newer appliances). Flues will be covered in the next
topic of this Section.
Regular boiler with three pipes:
1. Gas/oil (fuel supply).
2. Heating flow (hot water from boiler to radiators and hot
water cylinder)
3. Heating return (colder water from other end of radiator
circuit to boiler for re-heating).
RDSAP Manual March 2012
The hot water supply to the taps comes from the hot water cylinder,
often found in the airing cupboard. The stored hot water is heated
indirectly by the boiler. This means a heat exchanger or coil of
pipework is heated directly by the boiler and transfers that heat to
the stored water in the cylinder.
With a regular boiler, although you have a tank of hot water ready
to use, there are losses associated with the pipework between the
boiler and cylinder (primary pipework) and from the cylinder itself,
even when very well insulated.
Combination boiler Combination boilers (combi boilers) heat domestic hot water on
demand without the use of a hot water storage cylinder. A combi
boiler will be plumbed into the cold mains supply entering the
property, and when a hot tap is turned on, the fall in pressure in the
hot water pipes triggers the boiler to fire.
The boiler heats water from the cold mains supply within the boiler
casing, and circulates it to the hot taps on sinks, bath tubs etc. The
boiler will also be plumbed into the radiator circuit as normal, so a
combination boiler has more pipes entering the casing than the
conventional types. It is not necessary to remember what all these
pipes do, but for completeness the usual five pipes are listed here:
1. Heating flow (hot water from boiler to radiators).
2. Heating return (colder water from other end of radiator
circuit to boiler for re-heating).
3. Gas/oil (fuel supply).
4. Mains cold water (from the supply outside in the street).
5. Hot water supply (hot water from boiler to hot water taps in
the property).
Since the boiler can only heat up a certain amount of water at once,
the hot water flow might be slower than with conventional systems
using a hot water cylinder. Some combi boilers contain small stores
of hot water (usually about enough to fill a kitchen sink) to supply a
limited amount of hot water at a higher flow rate. Electric showers
are also commonly installed with these systems.
RDSAP Manual March 2012
Left: A combi boiler.
A combi boiler can be distinguished by:
More pipes entering the boiler case (count 5 or 6, rather
than the usual 3).
Boiler fires when the hot water is turned on.
Look for a pressure gauge on the front of the boiler.
There is no hot water cylinder.
Combi boilers tend to have fan-assisted flues as these are more
common on newer appliances. Flues will be covered in the next topic
of this Section.
Condensing boilers use a second heat exchanger to recover heat
Condensing regular
from the hot flue gases before they are exhausted through the flue.
boiler
This increases the overall efficiency of the appliance.
Above: A condensing boiler showing the larger diameter condensate drain.
Condensing boilers will have an extra pipe (a plastic pipe as the
acids in the condensate will corrode copper) to allow condensate
from hot flue gases to drain away. This makes four pipes on a
standard condensing boiler.
RDSAP Manual March 2012
1. Gas/oil (fuel supply).
2. Heating flow (hot water from boiler to radiators and hot water
cylinder).
3. Heating return (colder water from other end of radiator circuit to
boiler for re-heating).
4. Condensate drain (plastic pipe).
Other clues to help identify a condensing boiler:
A plastic drainpipe (1¼‘ or ¾‘ diameter) from the boiler to a
suitable drain, internal or external.
Most probably a fan assisted flue.
On a cold day in winter you may notice steam coming out of
the flue terminal.
Condensing combi
boiler
Cpsu–combined
primary storage
unit
Combi boilers can also be condensing, the plastic condensing pipe
should be visible.
This is a single appliance designed to provide both space heating
and domestic hot water, in which there is a burner that heats a
thermal store. The store must be at least 70 litres, if the store is a
different appliance from the boiler i.e. contained within a separate
overall casing, the system should be treated as a boiler with a hot
water cylinder.
CPSUs are entered by selecting heater type as boiler and boiler type
as CPSU. A CPSU is a boiler with an integral thermal store. The
thermal store must be greater than 70 litres (except electric CPSUs);
otherwise the system is simply a storage-combi and in RDSAP would
be entered as a combi boiler.
RDSAP Manual March 2012
A thermal store is a vessel for holding hot water, but unlike the hot
water cylinder that provides domestic hot water with a regular
boiler, the hot water within the store provides the hot water to the
radiator system.
The boiler heats the water in the thermal store directly and within
the store is a heat exchanger (coil of pipe) that provides the hot
water.
Sometimes a CPSU will have the thermal store separated from the
boiler unit. In these cases the RDSAP convention is to enter the
heating system as a regular boiler with cylinder. The volume and
insulation of the thermal store should be recorded against the hot
water cylinder details.
An electric CPSU must be a minimum of 270 litres.
Back boiler
A back boiler will usually be located out of sight within the chimney
breast. For gas-fired or solid fuel-fired room heaters with a back
boiler, the back boiler can be identified by water pipes entering the
appliance (or chimney breast) and sometimes by radiators in the
property with no separate boiler. For a gas or solid fuel fire with a
back boiler that feeds radiators you should enter the system as
Boiler in Main Heating, and then enter Back-boiler in the Boiler type.
The heating fuel should be specified appropriately.
For a gas or solid fuel fire with a back boiler that only provides hot
water (i.e. there are no radiators), then specify the heating type as
Room Heaters and choose the appropriate system, with (no rads)
.For a gas fire with a back boiler that provides space heating, the
back boiler should be entered as the main heating and the gas fire
should be recorded as secondary heating
For oil or solid fuel fires with back boilers, the fire should not be
entered as secondary heating.
Where the main heating incorporates a back boiler for water
heating, the water heating type should be referenced as being from
the main heating system.
RDSAP Manual March 2012
Range cooker
boilers
Kitchen ranges incorporate a boiler that delivers space heating,
space and water heating or just water heating.
To enter a kitchen range cooker boiler, choose Heater type Boiler
and Boiler type range cooker. If you have the make and model and
can locate the range cooker in the Product Database, you can select
from here. If not choose a default system. If the range cooker
provides hot water only, it should be selected from the water
heating page (see Section Seven) or enter it as main system 2 if it
can be located in the PCDF.
micro-CHP
Micro-CHP stands for micro combined heat and power. This refers to
a heating technology which generates heat and electricity
simultaneously, from the same energy source, in individual homes
or buildings. The main output of a micro-CHP system is heat with
some electricity generation, at a typical ratio of about 6:1 for
domestic appliances.
Any electricity generated and not used in the home can be exported
back to the grid. Micro-CHP systems are comparable in size and
shape to an ordinary, modern, domestic boiler and can be wall hung
like most boilers, or floor standing. Servicing costs and maintenance
are estimated to be similar to a standard boiler–although a specialist
will be required.
RDSAP Manual March 2012
PCDF
Micro-CHP units must be correctly sized for the dwelling, in order to
use the data from the PCDF. If you choose the micro-CHP unit from
the PCDF and get an error message about the plant size ratio:
―Error calculating Appendix N: The plant size ratio is too
big”.
The plant size ratio is calculated from the size of the micro-CHP unit
and the heat loss characteristics of the dwelling. A micro-CHP unit
must be correctly sized for a dwelling to work efficiently. If the plant
size ratio is too big, this means the micro-CHP unit is oversized for
the property (i.e. a small well insulated flat with a high output
micro-CHP unit.) Conversely, a micro-CHP with a small output in a
large poorly insulated dwelling may be undersized and cause a
calculation error.
If, when selecting a micro-CHP from the product database, you get a
plant size ratio error, you should enter a condensing boiler and add
addendum 5
Above: Baxi Ecogen Micro-CHP in appearance much like a standard boiler.
RDSAP Manual March 2012
There are no default micro-CHP systems. If you cannot locate the
micro-CHP unit in the product database, it should be entered as a
condensing boiler and include addendum 5.
Flue type
introduction
Spotting a flue on the outside of a house can help you locate and
identify the heating system within. It can provide you with useful
clues that can help you decide on the primary and secondary heating
systems within a property. With a little practice you will find yourself
automatically taking a mental note of the flues as you approach and
explore a property.
The flue type has an impact on the efficiency of the heating system.
The software uses the information to return a more accurate energy
rating. It is necessary to identify the presence of a fan-assisted flue,
as well as whether it is balanced or open as these will affect
calculating the SAP. For clarity, the typical flue types are described
in the following pages.
open flue
Open flues act just like a narrow chimney, and have a diameter of
around 200 mm (about 8‘). They rely on the drawing effect of
outside air to suck air from the appliance up the flue.
Open flues are predominantly vertical, with the minimum of bends
as these interfere with the airflow. Appliances with open flues are
not ‗room sealed‘ as they take air from inside a room, use it in the
combustion process and then exhaust the waste gases through the
flue to the outside. Appliances with open flues require ventilation
within the room; you may find an air brick or grille in the outside
wall of a room with an open flued appliance.
This type of flue tends to be found on older floor mounted boilers,
and these boilers are still very common. Other appliances that
typically use open flues are the solid fuel/wood-burning stoves and
gas fires.
RDSAP Manual March 2012
Left: Open flue schematic.
.
open flue–fan
assisted
It is unlikely but possible that you may come across a fan-assisted
open-flued appliance. In these circumstances it would be categorised
as open and fan-assisted.
RDSAP Manual March 2012
Balanced flues
Balanced flues are the larger, square flues that appear on the
outside walls of a property. They are about the size of a cake/biscuit
tin, and need to be this size as they rely on natural air movement
(rather than air being forced by a fan).
These flues are always found exactly on the other side of an external
wall to where the boiler/room heater is mounted. The flues run
horizontally through an external wall (as the natural air movement
only works over a short distance) and so will be mounted low down
on external walls for gas fires, and might be higher on the wall when
used with a wall mounted boiler.
Boilers and room heaters that use this type of flue are described as
‗room sealed‘. Outside air enters the boiler through the flue, is used
in the combustion process, and then is exhausted through the flue to
the outside once more, i.e., the combustion process is sealed from
the room itself.
.
.
Balanced flue schematic
RDSAP Manual March 2012
Fan assisted room
sealed
As the name suggests, these flues use a fan to ensure that the right
mix of air and fuel is supplied to the appliance.
As with balanced flues, they are room-sealed so only use air from
outside of the property, and exhaust air back outside. They are
therefore not classed as open flues.
This type of flue can accommodate more bends than other types, so
boilers need not be fixed to external walls, or have space for a
vertical flue directly above them (as with open flue appliances).
.
Above: Examples of fan-assisted flues.
Certain types of boiler may incorporate the use of fan assistance on
an open flue, rather than in conjunction with a room sealed
appliance. For boilers, both the flue type and whether it is fan
assisted need to be separately identified.
Flue gas heat recovery
introduction
A flue gas heat recovery system (FGHRS) recovers heat from the hot
flue gases and uses this to pre-heat the cold water going to a hot
water cylinder or combi boiler.
Flue gas heat recovery can only be used in conjunction with a gas
(LPG or mains gas) or oil condensing boiler.
There are no ‗default‘ FGHRS, it can only be selected from the
product database.
The system can be integral/specific to a certain boiler (Passive Flue
Gas Heat Recovery Device (PFGHRD) or generic/compatible with a
range of boilers (FGHRS).
RDSAP Manual March 2012
PFGHRD
If the flue gas recovery system is integral within the boiler or specific
to a particular boiler, this will be automatically identified when
selecting the boiler from the product database. For a PFGHRD you do
not need to select the flue gas recovery system from the product
database, the software will complete the relevant flue gas recovery
details from the information about the boiler.
FGHRS
A flue gas heat recovery that is separate from the boiler (normally
installed on top) must be selected from the product database. There
are different FGHRS are suitable for various boiler types, i.e. some
FGHSR are only compatible with combi boilers.
.
Heat store
PV
Some flue gas heat recovery systems for combi boilers incorporate a
small thermal store. This store uses heat transferred from the space
heating circuit to additonally pre-heat the hot water. The store will
be small and may be integral to the FGHRS. If the FGHRS has a
store these details will be held with the information in the product
database, you do not need to enter any store details.
Some FGHRS use PV to provide energy to am immersion within a
heat store. If this is the case the PV details will open up on the heat
recovery screen and you should enter the PV specification. The PV
system is likely to be small in comparison to a normal domestic
installation, 1 or 2 panels at most.
RDSAP Manual March 2012
Remember: flue gas heat recovery is only compatible with
condensing boilers.
RDSAP Manual March 2012
Main heating controls
introduction
The controls for the main heating system will differ with the type of
system. This section describes the different controls and how to
identify them and then describes the various options within the
software. Boiler controls are covered first and then the different
controls associated with other heating systems.
Types of control
room thermostats In most dwellings the room thermostat will be situated in the lounge
or hallway. The purpose of this heating control is to measure the
internal air temperature, and depending on the set temperature will
turn the heating system on or off.
In some cases you will come across dwellings with zoned heating
with more than one room thermostat. This allows the warmer living
areas of the house (e.g. lounge) to be assessed independently of
say, the bedrooms, which could be kept cooler. (See Full Zone
Control, later in this section.)
Above: This room thermostat also has a delayed start button. When pressed
it stops the thermostat calling for the heating to come on, usually delaying
the heating by an hour for each press.
A programmable room thermostat allows the heating times and
temperature to be set from the one unit. This means it counts both
as a room thermostat and a programmer on the survey form.
RDSAP Manual March 2012
Programmer
The programmer is nearly always found near to the boiler or the hot
water tank. It is basically a timer that only allows the heating and
hot water systems to operate for certain times of day. Most
programmers will allow for independently timed operation of the
space and water heating.
Most central heating systems have a programmer (or time clock)
otherwise the boiler/heating unit would be on continuously.
Above: Analogue and digital programmers with separate times for water and
space heating.
Sometimes on an inspection it may appear a programmer is not
present (despite there being other heating controls; thermostat,
TRVs). Note that sometimes programming (timer) control is provided
integrally within a boiler.
TRVs
Thermostatic radiator valves (TRVs) are used to control heat locally
i.e. on each radiator. The hot water flow rate through the radiator is
adjusted in line with the setting on the TRV, thereby altering the
heat output from the radiator and allowing different temperatures to
be obtained. A TRV differs from a cut off (or on/off) valve on a
radiator in that it has numbers usually 0 or * to 6 or 7.
Above left: A radiator cut off valve; above right: A typical TRV.
RDSAP Manual March 2012
Time and
temperature zone
control
This allows both the heating times and temperatures of two or more
zones to be set independently of each other, for example one
upstairs and one downstairs. This involves separate plumbing
circuits, either with their own programmers, or separate channels in
the same programmer. (By contrast TRVs provide only independent
temperature control).
Boiler interlock
Where there is a boiler interlock, the wiring of the boiler controls is
such that the boiler runs only when there is a demand for either
heating or hot water. The pump is also controlled by the interlock so
that both boiler and pump turn off. Usually missing from older
systems, the lack of this control arrangement causes wasteful ‗boiler
cycling‘. Without an interlock, the boiler keeps running (turning on
and off at brief intervals) even though no heat is required. This
results in a 5% reduction in operating efficiency.
For the purpose of the SAP, an interlocked system is one in which
both the space and water heating are interlocked. For solid-fuel
boilers and dry-core electric boilers the question of boiler interlock is
irrelevant. It is not usually possible to assess the presence of a boiler
interlock in a short inspection, so the software deduces whether a
boiler interlock is present based on the controls identified–there is no
need for the Assessor to look for this feature.
Flow switch/bypass This device switches the boiler off when flow stops in the boiler flow
line, because the TRVs are all closed. It is situated close to the boiler
or cylinder with an electrical connection. A flow switch may be
installed as an alternative to a room stat. Flow switches are not
included in RDSAP because they are difficult to identify in a site
inspection. In the unlikely event of your finding one in an
Inspection, you should enter it as a bypass.
RDSAP Manual March 2012
A Boiler Energy Manager is a device used in conjunction with TRVs,
which controls the water temperature to suit the external
temperature. It also senses the return water temperature and
Boiler energy
manager
switches off the boiler when this rises above a certain level. For the
purposes of the SAP, the latter function is equivalent to a hard-wired
interlock.
15 RESPON
SE
5
BOILER TEMPERATURE C0
1
HEATINGSAVING
5 7 9 11
3
13
WATE
R
1
15
RESPONSE RATE
OFF ON
C OM PENSATOR
An exte rna l
tem p era ture
Sensor
BEM 5000
0
OUTSIDE TEMPERATURE C
There are numerous products on the market claiming to be Boiler
Energy Managers but which in fact only delay boiler firing, similar to
a delayed start thermostat. These do not count as Boiler Energy
Managers for the SAP.
Delayed start
thermostat
This is a room thermostat that delays the initial switch-on at the
start of a heating period if the room temperature has not fallen as
much as usual during the off-period. It does not advance the switchon in cold weather.
Delayed start thermostats are not included in RDSAP because they
are difficult to identify in a site inspection. In the unlikely event of
your finding one in an Inspection, you should enter it as a normal
room thermostat.
RDSAP Manual March 2012
Options for control types
controls for boilers
no time or
Where there is no timing or temperature control for the heating
temperature control system. The thermostat that controls the temperature of the water
leaving the boiler (the boiler thermostat) can be used to (crudely)
control the room temperature. However, this is not recognised as an
option for control types.
Programmer only
Where the heating system can be set to come on and turn off on
certain parts of the day. There is usually separate timing for water
and space heating. As there are no thermostat heating controls in
the dwelling the temperature cannot be adjusted, the controls relate
simply to when the heating occurs.
Room thermostat only Where there is temperature control only and the times for the
heating to be activated cannot be specified. This relates solely to
space heating. It works by sensing the air temperature that has been
specified, e.g. 21°C. When the temperature rises above the setting,
the thermostat tells the central heating system to switch off
(normally the pump)–in turn this stops the boiler firing.
programmer and
room thermostat
Where there is both a programmer and room thermostat present.
This can also relate to programmable room thermostats (a
thermostat and programmer in the same unit). The timing of space
heating and water heating can be specified independently from one
another.
TRVs and bypass
Where you identify TRVs but no room thermostat or programmer,
there will normally be a bypass, as this is simply a loop of pipe or an
open radiator (radiator without a TRV). It allows the hot water to
continue to circulate when all the TRVs have closed down; this
ensures the correct temperature information is received by the
control unit for it to adjust the boiler output accordingly. This is
wasteful compared to having a room stat, because it allows the
boiler to continue firing even when no heat is needed. There is no
need to search for the bypass if there are TRVs and no programmer
or no room stat, this is the controls that should be entered.
TRVs, programmer
Where you identify TRVs and a programmer, but no room
RDSAP Manual March 2012
and bypass
thermostat, there will normally be a bypass.
No boiler interlock is possible since there is no room stat to turn off
the boiler when there is no need for heat. A bypass is often located
as close to the boiler as possible.
There is no need to search for the bypass if there are TRVs and a
programmer but no room thermostat; this is the controls that should
be entered. A flow switch may form part of this arrangement but this
is ignored for RDSAP.
programmer room
stat and TRVss
Where there is a programmer, a room thermostat and over 50% of
the radiators in a dwelling contain TRVs. If less than 50% of
radiators have a TRV, the dwelling should not be assessed as having
TRVs. TRVs should not, ideally, be located in the same room where
the room thermostat is fitted as it could make the thermostat
sensing inaccurate.
programmer and at Where there is a programmer and two thermostats located within a
least two room
dwelling. As there is only one programmer there is no zone timing
thermostats
and therefore separate temperatures can be specified in different
zones but they turn on and off at the same time. This is NOT time
and temperature zone control.
TRVs, programmer
and boiler energy
manager
Where there is a programmer, more than 50% of the radiators
containing TRVs, and a boiler energy manager. A boiler energy
manager is an intelligent boiler/burner management control that
reduces the unnecessary firing of burners and aids tighter control on
temperatures. It works by sensing the water flow and return
temperatures in conjunction with the TRVs (there are sensors on
both flow and return pipes).
The return temperature is used to determine when to reduce the
boiler setting and when to extend the firing cycle. This allows the
boiler to determine the optimum firing pattern by automatically
matching hot water temperatures on demand. When the
temperature is reached the boiler switches off, similarly the boiler.
RDSAP Manual March 2012
time and
temperature
zone control
A control system which can independently control the temperature
and heating time in each zone. This will require separate heating
circuits, each with its own programmer or a single multi-channel
programmer (TRVs do not constitute zone control). This means that
different parts of the house can be maintained at different
temperatures for different periods of time.
There are three types of control that can be used with electric
controls for storage
storage heaters: manual charge; automatic charge; and CELECTheaters
type. Celect controls are not included in RDSAP and are treated as
automatic charge. Determining if the storage heaters have manual
or automatic charge control can be difficult. The best way to check is
to take the model number and check on the manufacturer‘s website.
manual charge
control
As the name suggests this is a simple hand operated control on the
storage heater. With manual charge control the user must set the
input (normally a dial with a choice of 1-9, 9 being the highest
charge used in winter). Of course this means that if the night is
unusually warm the storage heater will still draw the same charge as
if it was very cold. The user is then left with lots of unwanted heat
the next day.
automatic charge
controls
An automatic charge system has a thermostatic sensor either
external to the heater itself or on the wall. This sensor determines
the amount of charge drawn based on the ambient temperature. If it
is warmer less charge is drawn overnight. Therefore the storage
heater is ‗in tune‘ with the ambient temperature and according to
manufacturers this can lead to cost savings of up to 15 per cent. If in
doubt as to whether the storage heater is automatically charged or
not you should take the model name and number and search for it
online.
controls for warm
air systems
Similar to the options for boilers, but there are fewer options as
TRVs are not relevant for warm air systems:
(including warm air
heat pumps)
No stat control of room temperature.
Room stat only.
Programmer only.
Programmer and room stat.
Programmer and at least 2 room stats.
Time and temperature zone control.
RDSAP Manual March 2012
Note the temperature zone control option. If there are room
controls for electric thermostats in each zone (possible each room) but no programmer,
ceiling heating
select this option.
No stat control of room temperature.
Room stat only.
Programmer only.
Programmer and room stat.
Temperature zone control
Time and temperature zone control.
The options are mostly self-explanatory:
controls for room
heaters
No stat control of room temperature should be used when
there are no controls, or a simple on-off control.
Appliance stat only.
Room thermostats only.
Appliance stat and programmer
Programmer and room stat.
For wet heat pump systems the control options are as follows:
controls for heat
pumps with
radiators or
underfloor heating
No stat control of room temperature.
Room stat only.
Programmer only.
Programmer, TRVs and bypass.
Programmer and room stat.
Programmer and at least 2 room stats.
Time and temperature zone control
RDSAP Manual March 2012
Community heating controls
There are six types of heating controls for community heating
systems that are split into two categories. These are categorised as
either flat-rate charging or from a charging system linked to the use
of the community heating system:
Flat rate charging: where households pay for the heat
according to a fixed monthly or annual amount, not related
to the amount of heat actually used. This applies even if the
charges vary within a scheme for other reasons, e.g.
dwelling size.
Charging system: where the charges are substantially
related to the amount of heat used, usually linked to the use
of heat meters.
The options are then self explanatory:
Flat rate charging, no thermostatic control of room
temperature.
Flat rate charging, programmer no room thermostat
Flat rate charging, room thermostat only.
Flat rate charging and TRVs.
Flat rate charging, programmer and TRVs.
Charging system linked to use and room thermostat only.
Charging system linked to use, programmer and room
thermostat only.
Charging system linked to use and TRVs.
Charging system linked to use, programmer and TRVs.
RDSAP Manual March 2012
Types of secondary heating
mains gas room
heaters
Some of the most common room heater types are mains gas units.
These are available in a range of types but for RDSAP purposes are
categorised as follows:
Gas (including LPG) room heaters:
Flue Type
Gas fire, open flue, pre-1980 (open fronted)
Open flue
Gas fire, open flue, 1980 or later (open fronted), sitting
proud of, and sealed to, fireplace opening
Open flue
Gas fire or wall heater, balanced flue
Balanced flue
Gas fire, closed fronted, fan assisted
Balanced flue
Condensing gas fire
Flush fitting Live Fuel Effect gas fire (open fronted),
sealed to fireplace opening
Balanced flue
Open flue
Efficiency
50%
63%
58%
72%
85%
40%
Flush fitting Live Fuel Effect gas fire (open fronted), fan
assisted, sealed to fireplace opening
Open flue
45%
Decorative Fuel Effect gas fire, open to chimney
20%
Gas fire, flueless
Open fireplace
No flue
90%
This refers to an ‗open‘ flame effect gas fire underneath an open
Decorative fuel
chimney. The energy calculations assume that these heaters are only
effect gas fire open
20% efficient as most of the heat escapes up the chimney.
to chimney
Above: Examples of decorative fuel effect gas fires.
RDSAP Manual March 2012
Left: Cross section illustrating a decorative
fuel effect fire open to the chimney.
Flush fitting live
fuel effect gas fire
(open fronted),
sealed to fireplace
opening
Whilst still an open flame-effect gas fire, these units are more
efficient than the above as they are sealed to the fireplace opening
and therefore provide a more restrictive and controlled flow of
combustion ventilation. Overall efficiency is increased from 20% to
40% and these appliances may also be fitted with a back boiler.
Note: The fact that they are sealed to the fireplace opening will
mean that the fireplace is no longer open for ventilation purposes
and will not be included in the open fireplace count.
Above: Examples of inset fuel effect gas fires.
RDSAP Manual March 2012
Above: Cross-section illustrating an inset Live Fuel Effect gas fire which is
sealed to the fireplace opening
flush fitting live
fuel effect gas fire
(open fronted), fan
assisted, sealed to
fireplace opening
As for ‗flush fitting live fuel effect gas fire (open fronted), sealed to
fireplace opening‘ but with fan assistance improves the assumed
efficiency by 5% to 45%.
gas fire, open flue,
pre-1980
(open fronted)
Above: Example of a pre-1980 gas fire; assumed efficiency of 50%.
RDSAP Manual March 2012
gas fire or wall
heater, balanced
flue
Above: Examples of a gas fire and wall heater, both with balanced flues.
Assumed efficiency of 58%. Gas fires with balanced flues must be closed
fronted.
gas fire, open flue,
1980 or later:
(open-fronted),
sitting proud of and
sealed to fireplace
opening
Above: Example of post-1980 open flue gas fire. Assumed efficiency of 63%.
Gas fires can be open-or closed-fronted. Open-fronted means that
the fuel bed and combustion gases are not sealed from the room in
which the gas fire is fitted. Such an open fire may or may not have
a glass panel in front of the fuel bed but the panel will not be sealed
to the front of the fire. Closed-fronted means the fuel bed and
combustion gases are sealed (generally with a glass panel sealed to
the front of the fire) from the room in which the gas fire is fitted. Any
openings around the glass panel mean that the fire is not closedfronted.
RDSAP Manual March 2012
gas fire, closedfronted, fan
assisted
Above: Example of a closed fronted fan assisted gas fire, Assumed efficiency
of 72% . This fire will have a glass front and has an integral fan which blows
the convected heat back into the room.
condensing gas fire It is extremely rare to come across one of these types. Assumed
efficiency of 85%.
flueless gas fires
As their name suggests these gas fires require no flue and therefore
need not be mounted on an external wall. The heat loss normally
associated with the flue is removed, resulting in a highly efficient
appliance.
Left: cross-section shows the operation of a
flueless gas fire. The assumed efficiency is 90%.
When attempting to identify a gas fire type, first identify whether it
is as live fuel effect fire or otherwise, which will immediately narrow
down the options for selection. When in doubt always opt for the fire
with the lower efficiency.
RDSAP Manual March 2012
solid fuel open fire These are true solid fuel open fires: open to the chimney with real
flames. If used regularly they will tend to have a guard in front to
prevent hot coals escaping into the room. Expect to see ash and the
tools for stoking the fire near the hearth.
Above: Example of a solid fuel, open fire.
solid fuel closed
fire/closed room
heater
Here the flames are enclosed behind a door. These closed fires tend
not to have guards in front of them. Flames can normally be viewed
through a glazed window in the door(s). There is usually an open
flue, which may feed into the chimney if the unit sits in a fireplace.
Above: Example of a solid fuel, closed fire.
Electric room
heaters
Fixed electric room heaters providing secondary heating can take the
form of panel convector heaters, fan heaters and radiant heaters.
Modern electric fires often look quite like their gas equivalents, but
even though they try to mimic the flame effect they are easy to
distinguish from gas units when ‗lit‘.
They are more difficult to tell apart when not switched on, but there
will be no gas supply pipe present, and on closer inspection you
might be able to spot an on- switch or decorative bulb. Electric fires
may incorporate a radiant bar heating component or a fan heater.
RDSAP Manual March 2012
Electric room heaters can also consist of wall mounted panel
convector or fan convector heaters and radiant bar fires mounted at
high or low level.
bio-ethanol room
heater
A bioethanol fire uses liquid or gel alcohol based fuel. Rather than
burning the actual fuel, they burn the vapours given off by the fuel.
It requires no flue and therefore can be placed anywhere in a room,
not just against a wall. These types of fire are becoming more
popular in flats and apartments where there is no chimney or place
for a flue. A bioethanol fire will have no gas supply.
These are expensive to run so the SAP rating will go down but they
are environmentally friendly so the Environmental Impact (EI) rating
will go up.
summary
In this Section you have learnt how to:
Categorise the heating systems present in a property into the
main and secondary systems
Complete the details for main and secondary systems
Identify different heating fuels
Understand the difference between boiler types and flue
options
Describe relevant main heating controls
If you feel comfortable with what you have learnt in this Section,
then have a go at the following Self-Test Questions and move on to
the next Section.
RDSAP Manual March 2012
self-test:
Section six
Do you understand all the key points made in this Section? Test your
knowledge here! If you get stuck then note down your best guess, go
and find the answer from the pages of the Section.
Q1 (1 mark)
What type of boiler is this?
_________________________
_________________________
Q2 (1 mark)
What type of flue is this?
_________________________
_________________________
Q3 (1 mark)
Which appliance has the higher efficiency, (a) or (b)? ____________
(a) a gas flame effect fire, open to chimney
or
(b) a gas flame effect fire, sealed to fireplace opening
Q4 (2 marks)
Name two heating controls typically found with a boiler and radiator
system?
1. _________________________________________________
2. _________________________________________________
RDSAP Manual March 2012
Q5 (1 mark)
Choose the correct answer to the following.
Where would you expect to find a room thermostat control?________
(a) in the airing cupboard
(b) in the kitchen
(c) in the hallway
Q6 (2 marks)
(a) What type of appliance is this?
_________________________
_________________________
(b) Would you record it on the survey form? Yes / No
Q7 (1 mark)
What type of storage heater is this?
_________________________
_________________________
Q8 (3 marks)
Can these heating systems be described as secondary
heating?
(a) storage heaters
Yes / No
(b) gas room heater
Yes / No
(c) electric portable heaters
Yes / No
RDSAP Manual March 2012
Q9 (1 mark)
What fuel does this appliance use?
_________________________
_________________________
Q10 (2 marks)
Can the following systems be recorded in RDSAP?
(a) electric under floor heating
Yes / No
(b) electric ceiling heating
Yes / No
Q11 (3 marks)
For each boiler type below, how many pipes would you usually
count entering the boiler casing?
(a) regular condensing boiler
(b) regular boiler
(c) combination boiler
________________
________________
________________
Q12 (2 marks)
Which of the following boilers are compatible with a flue gas
heat recovery system?
(a) regular condensing oil boiler
Yes / No
(b) solid fuel boiler
Yes / No
(c) LPG condensing combi
Yes / No
The answers to this self-test can be found on the next page
Section 6 Self-test result: ________ /21
RDSAP Manual March 2012
self-test answers
Q1
Combination boiler
Q2
Fanned flue/ fan-assisted flue
Q3
(b) The ―gas flame effect fire, sealed to fireplace opening‖ has the higher efficiency.
Q4
Two typical boiler and radiator heating controls:
1. programmer/timer
2. room thermostat
3. thermostatic radiator valves – ‗TRVs‘
Q5
(c) in the hallway.
This is not the ideal location though. Room thermostats should be located in the
warmest living area i.e. the lounge/living room, and away from draughts. Thermostats
in hallways usually need to be set to a lower level, because otherwise by the time the
hallway gets up to temperature, the rest of the dwelling is overheating and becomes
uncomfortable. On the other hand, if the hallway is heated by solar gains and the rest
of the house is north facing, the hall thermostat may switch the heating off too soon,
leaving the lounge a bit chilly!
Q6
(a) The appliance is a form of portable electric heating – an oil filled radiator.
Don‘t make the mistake of recording it on the form under Heat emitter:
Radiator; this refers to a wet heating system radiator.
(b) No, it should not be recorded on the form.
Q7
Q8
Q9
Q10
The appliance is a modern, slim line storage heater.
(a) No (b) Yes (c) No
Electricity
(a) Yes as either on or off peak depending on the system (b) Yes
Q11 (a)
A regular condensing boiler will have 4 pipes
Q11 (b)
A regular boiler will have 3 pipes
Q11 (c)
A combination boiler will have 5 or 6 pipes
Q12
(a) yes (b) No - FGHR is only compatible with condensing boilers (c) yes
Score:
/21
RDSAP Manual March 2012
Section seven | water heating
Water heating
introduction
The method of water heating must be specified for every property. In
most cases the water heating will be from the main/primary heating
system or by immersion heater(s). In reality, hot water demand varies
with the number and habits of the occupants. In RDSAP it is the hot
water demand is calculated from an assumed number of occupants
derived from the floor area of the dwelling. The hot water energy
requirement takes into account losses in heating, storage and
distributing the water around the house. For most systems, the losses
are due to the heat released into the dwelling from storage cylinders
and the distribution pipe work.
When water heating is supplied by a system using off-peak electricity,
the calculation assumes that a proportion (determined by the floor area
and cylinder size) of the water heating will take place at on-peak times.
water heating type
How you enter the hot water system will depend to some extent on the
heating systems that are present. Clearly, a gas boiler will usually
provide the hot water as well as the heating, whereas a storage heater
system will not.
none
Use this option when there is no water heating system installed. The
software will use electric immersion for the purpose of the calculation.
The DEA is not expected to ascertain if a water heating system is
working or not, so if there is a water heating system present this should
be recorded, regardless of whether the DEA thinks that it is working or
not.
Regular
The term regular simply refers to standard water heating system.
Range cooker
This should be selected if the range cooker heats the hot water. You will
then need to select the relevant system.
RDSAP Manual March 2012
Hot water only
community
scheme
This option applies if the property does not have its own independent
hot water system but shares a system with one or more other
properties. This should only be selected where the community scheme
provides hot water only. If the community scheme provides space
heating as well, the community heating should be entered for the main
heating with water heating type ‗regular‟ and water heating system
from main.
You will then need to select whether the community heating is from
boilers, CHP or Heat pump, and also the relevant fuel.
water heating system
This should be selected if either of the two possible main heating
from main
systems also heats the hot
heating 1 or 2
water for a property.
From secondary
system
RDSAP Manual March 2012
Electric
immersion
Immersion heaters are essentially just a larger version of the heating
element found in normal jug kettles. They protrude from the side of the
cylinder and contain a built-in thermostat which is usually factory-set to
60 degrees Celsius.
If you select electric immersion, you will need to identify whether this is
a single or dual immersion.
There are two common circumstances for identifying a single
immersion:
Where a dwelling has older style electric storage heaters there
will often be a poorly insulated hot water cylinder with a single
immersion
Single immersion heaters are very often found in cylinders that
are connected up to a boiler and radiator system. However, in
this case the immersion heater will be an emergency backup for
use when the boiler is being serviced, or has broken down.
These back up immersion heaters should be ignored when
completing the survey form.
If the immersion heater is a backup, the cylinder will be an indirect
cylinder (you will see extra pipes carrying the hot water from the
boiler); this is a clue that the immersion heater is not the main hot
water system.
To identify a single immersion heater, first select electric immersion for
the water heating system then choose single in the immersion section.
If a hot water cylinder is heated from the main heating system, e.g. the
boiler, then do not record the single backup immersion on the survey
form (this will indicate to the software that all the water heating is from
electricity). This will make the energy rating of the property worse than
it should be. The correct water heating entry is from boiler/main
heating.
RDSAP Manual March 2012
RDSAP Manual March 2012
Dual immersion True dual immersion hot water cylinders are normally only found with
electric heating systems that operate on a dual meter*, usually charged
on the Economy 7 or Economy 10 tariffs.
*Records two sets of numbers, one for the on-peak electricity and the other, offpeak, charged at the cheaper rate.
Dual immersion cylinders have two immersion heaters. For larger
cylinders (typically 210 litres) this will consist of a bottom entry
immersion for heating the whole of the water overnight on the off-peak
rate and a top entry immersion, normally located about one-third down
from the top of the cylinder, to provide faster top-up as and when
required on the on-peak rate. Alternatively, some smaller cylinders will
have a two-in-one immersion heater with two elements (one long and
one short), with the longer element heating the whole of the cylinder
during off-peak periods and the shorter immersion providing a partial
top-up during the day. The two-in-one type can be distinguished by two
supply wires entering a single immersion heater end-cap and there will
often be a local timer controlling the two heaters.
There is one other type of two-in-one immersion heater occasionally
found in older properties. These are usually attached to a switch with a
sink/bath option. They operate in a similar way to the system described
above, with the bath option heating the whole cylinder and the sink
option only heating a smaller volume at the top of the tank. However,
this is still classified as a single immersion heater since the electricity
used is the same for both elements for these particular systems.
Dual immersion systems usually use a large hot water cylinder, since
this way they gain most benefit from the cheaper, off-peak rate. To
identify a dual immersion heater in the software, first select electric
immersion as the water heating system and then choose dual in the
immersion section.
Water heating via single or dual immersion is charged at a mix of offpeak and on-peak, depending on what time of day the water is heated.
There are tariff plans available that link the water heating directly to the
off-peak meter, so that the cheaper price is always applied to the water
heating regardless of the time of day. These tariffs are fairly rare in
England and Wales, and tend to be termed ‗24-hour space and water
heating tariffs‘. It is far more likely that a property operates on the
usual Economy 7 or Economy 10 tariffs, in which case you will find the
single and dual immersion options more applicable.
RDSAP Manual March 2012
Electric
instantaneous
Electric instantaneous water heaters are often wall mounted and placed
over or under each sink outlet. They can be used to feed single outlets
or one unit may be sized and plumbed to provide several hot water
outlets. Instantaneous electric water heaters are expensive to run
because they use on-peak electricity.
Instantaneous electric water heaters require much higher power ratings
than small direct storage units and would normally only be used for
items such as electric showers. In the unlikely event that the only hot
water available is via an electric shower, record this as the water
heating option.
single-point gas Similar to instantaneous electric water heating, single-point heaters can
only supply hot water to one basin. They are normally wall mounted by
each basin and can be identified by the visible gas supply pipe. There
will often be a visible pilot light through a window in the unit and can
incorporate a small store of hot water or may be fully instantaneous in
operation.
Multi-point gas Gas multi-point water heaters can provide hot water to a number of
outlets. One multi-point unit can supply hot water to the kitchen and
bathroom within a property. They are often found in the bathroom.
Both single-point and multi-point gas heaters work like a combination
boiler, heating cold water directly from the mains supply. The important
difference is that they only use this supply for domestic hot water, not
to feed a heating/radiator circuit.
For both multi-point and single-point gas water heaters, you need to
choose the fuel type from mains gas, LPG, LPG special condition 18 and
bottled LPG.
Boiler/circulator
(water heating
If there is a boiler or circulator that provides water heating only, and
the boiler could not be located in the product database (in which case
only)
use main heating 2), select this option. A circulator is a small boiler that
provides hot water direct to the cylinder (rather than indirectly as a
regular boiler does). You will then need to select the relevant fuel.
RDSAP Manual March 2012
Hot water cylinder size
introduction
The size of the hot water cylinder changes depending on the size of the
property and the type of system it is part of. Individual properties may
differ, but listed below is what you would typically expect to see.
Electric cylinders tend to be oversized for the property. Gas/oil cylinders
will be normal in size for small properties and increase with size of
dwelling.
Solid fuel cylinders will tend to be large. They need to be big to avoid
the water overheating, as the heating appliances can produce very large
amounts of heat and are not as controllable as other systems.
The DEA must measure each cylinder where possible to do so. It may
be that there will be a label that gives a volume in litres or alternatively
the height and diameter of the cylinder. Make a note of these and refer
measuring
cylinders in
practice
to the chart on page 8.
This is the most common size of cylinder; you will probably find this size
cylinder in average sized terraces and semi-detached houses that use a
boiler and radiator system. Flats and maisonettes with boilers and
normal
(90–130 litres)
radiators will tend to have a cylinder this size too.
This is more likely for larger houses, up to four bedrooms, running a
boiler and radiator system. Solid fuel boilers are likely to have a
medium cylinder and this is also the most likely option for small
medium
(131–170 litres)
properties using off-peak electric water heating (cylinders tend to be
larger with electric immersions to charge a good store of water on the
cheaper overnight tariff).
large
(over 170 litres)
This option is commonly found in slightly larger properties with electric
water heating (e.g., three-and four-bedroom properties) and large
properties with radiator systems (typically four double-bedrooms and
over).
no cylinder
You should tick this option where there is community heating and hot
water with no individual cylinders within the dwellings.
no access
Use this option when you know that there is a cylinder present, but it is
impossible to identify the size, perhaps due to it being boxed in. In this
case the software will use the most appropriate default for the size and
insulation, based upon the heating system and age of the dwelling.
RDSAP Manual March 2012
RDSAP Manual March 2012
If you select no access, there will be no recommendations made for
cylinder insulation. This is because what is being recommended might
already be installed.
cylinder sizing chart
Water content (litres) for different size cylinders:
Height in mm without insulation
Cylinder diameter in mm without insulation
300
350
375
400
425
450
600
35
48
55
60
70
77
750
45
62
70
80
90
98
825
50
69
78
89
100
109
900
55
74
87
96
110
120
150
975
60
83
95
107
120
135
164
1050
65
90
103
115
130
144
178
257
1200
75
103
118
134
150
166
200
290
1350
85
116
133
152
170
194
234
339
1500
95
130
148
170
190
218
255
370
180
206
230
265
320
450
1800
500
600
Some common cylinder size
825 x 450
110 litres
900 x 400
96
900 x 450
120
1050 x 400
115
1050 x 450
144
1500 x 450
218
Hot water cylinder insulation
Insulation
Insulation is entered in the software in two sections, insulation and thickness.
none
This option should be used where a hot water cylinder has no jacket
or spray foam insulation, or occasionally where there is a jacket in
such poor condition that it might as well not be there.
Jacket
Hot water cylinder jackets only provide good insulation if they are
RDSAP Manual March 2012
thick, and are a snug fit.
Spray foam
Spray foam cylinder insulation is a better insulation material than
glass-fibre in a jacket. E even though it may appear thinner, it
provides a more uniform layer of insulation and is factory fitted as
standard on most new cylinders.
Above: spray foam cylinder insulation.
Thickness
Gaps in the jacket where you can see the cylinder dramatically
reduce the overall effect of the insulation. Therefore, if the jacket is
in poor condition you should downgrade to a thickness that is
actually less than your measurement.
If a customer has a badly fitting jacket they will then receive advice
in their EPC to fit an additional thick jacket snugly over the top of
the original. Otherwise, choose the closest option in the list to the
thickness you have measured. The list options are: 12, 25, 38, 50,
80, 120, 160 mm.
The thicknesses are appropriate to both spray foam and cylinder
jacket insulation types.
RDSAP Manual March 2012
Pre-insulated
encapsulated
cylinders
In some cases cylinders will be supplied insulated and encapsulated
in metal or plastic covering and will often be of unvented design.
Whilst the unvented function is of no consequence as far as RDSAP is
concerned, these cylinders should be assumed to incorporate 50 mm
of spray foam insulation.
Left: Insulated and encapsulated.
Thermal stores
Some modern systems incorporate the use of a thermal store for
heating and hot water supply. Thermal stores effectively reverse the
primary and secondary functions of a standard cylinder, thereby
using the stored reservoir of hot water for the space heating and an
indirect heating coil for the water heating to provide mains pressure
hot water.
Thermal stores should be input as cylinders of the same volume as
the thermal store, with insulation again defaulted to spray foam of
50 mm thickness. Ignore any back up electric heating that may be
present with a thermal store.
Left: Thermal store.
non-cylindrical
water storage
Some older systems incorporate the use of a square tank for hot
water storage rather than a cylinder. In these circumstances the
store will be entered into RDSAP as a cylinder of equivalent volume
to the actual store, with jacket insulation of a thickness equivalent to
the thickness of the walls of the square tank if this insulation can be
seen and potentially measured.
RDSAP Manual March 2012
Hot water controls
programmer
cylinder
thermostat
Heating programmers normally allow the householder to set the
space and water heating times independently, but for RDSAP there
is no need to specify independent space and water heating control.
Reducing the temperature of the water in the hot water cylinder has
a large impact on the cost of water heating within the home. As
water gets hotter, it also loses heat more rapidly, so to keep the
temperature rising, more and more energy is required.
Keeping this in mind, it is well worth reducing the target
temperature of the hot water cylinder, even by 5 or 10 degrees as
this can quickly produce real savings.
A cylinder thermostat is a cheap way of providing these savings.
Without one, the water in the hot water cylinder will be heated to far
higher temperatures than required, typically in excess of 80oC. This
is the water temperature required for radiators, and is far too hot for
running baths etc.
A cylinder thermostat should be set to an ideal temperature of 60oC.
This is high enough to minimise the level of harmful bacteria whilst
still producing improvements in energy efficiency. It also knocks a
typical 15oC off the water-heating target. Remember this top-end
temperature reduction removes the really expensive last bit of water
heating.
Above: Cylinder thermostats, both these examples are fitted to spray foam
insulated cylinders.
Electric immersion heaters normally incorporate a thermostat in
their construction. Whilst the adjustment can normally be made
under the cap of the immersion heater, which may also expose live
electrical connections, there is no need to identify its presence as
the ‗built-in‘ thermostatic control within the immersion heater is
automatically assumed within RDSAP.
RDSAP Manual March 2012
You may occasionally come across a valve that looks like a TRV
attached to one of the pipes entering the cylinder. These are known
as cytrol valves and are not recognised in RDSAP. Whilst they can
regulate the temperature within the cylinder, they are not wired to
the boiler and therefore do not prevent the boiler cycling when the
temperature in the cylinder is reached.
Above: A cytrol
valve.
Bath and shower details
introduction
The details of the bathrooms and showers present need to be
collected to inform the recommendation for waste water heat
recovery.
You will need to collect the total number of rooms with a bath and/or
shower, this includes electric instantaneous showers. Include any
en-suites that contain either a bath or a shower. A downstairs
cloakroom with only a toilet and a sink should not be included in the
count.
The number of mixer showers need to be assessed, as waste water
heat recovery is only applicable to mixer showers. This includes
power mixer showers but not electric instantaneous showers. In
RDSAP a mixer shower is defined as:
“A shower where the hot water is provided by a boiler (combi
or regular), heat pump or immersion heater. A mixer shower
attached to bath taps is recorded as a mixer shower only if
there is a permanent bracket over the bath and there is a
Above: Mixer
shower.
shower curtain or screen “
You should record separately mixer showers in rooms with a bath
and those in rooms with no bath.
Remember: an electric instantaneous shower (IES) is not a mixer
shower.
RDSAP Manual March 2012
Waste water heat recovery
introduction
A waste water heat recovery system (WWHRS) is a device that
recovers the heat from the warm waste water of a shower and uses
it to pre-heat the cold feed to a hot water cylinder or combi boiler
and shower.
Waste water heat recovery is only compatible with mixer showers.
There is no default system and it can only be recorded if it is located
in the product database.
An installed WWHRS would not be visible to an DEA, so you will need
evidence to record the presence of one. This evidence should include
the make and model.
Left: a typical WWHRS installation
Data entry
RDSAP can accommodate up to two WWHRS, you will should collect
the make and model of the system to enable location in the product
database as well as the following for each WWHRS:
The number of mixer showers connected to the WWHRS in
rooms with a bath
The number of mixer showers connected to the WWHRS in
rooms without a bath
RDSAP Manual March 2012
Self-test:
Section seven
Do you understand all the key points made in this Section? Test your
knowledge here! If you get stuck then note down your best guess, go
and find the answer from the pages of the Section.
Q1 (1 mark)
What size of hot water cylinder would you expect to find in a 2 bed
semi with standard gas and radiator heating system?
(a) Normal 90-130 L
(b) Medium 131-170L
(c) Large >170L
Q2 (1 marks)
How would you record the immersion type for a house with electric
storage heating and a hot water cylinder with two immersion caps
visible.
(a) single
(b) dual
Q3 (1 marks)
What is the control used to limit the water temperature in a hot
water cylinder?
___________________________
Q4 (4 marks)
Answer true or false to the following statements
(a) The ideal temperature to set a hot water cylinder thermostat
is 60oC.
(b) Gas single point water heaters are so called because they
provide all the domestic hot water from a central appliance.
(c) When recording the thickness of a very loose cylinder jacket,
you should choose the option that is smaller than your actual
measurement
(d) Spray foam insulation is a better form of insulation than a
jacket of the same thickness.
RDSAP Manual March 2012
Q5 (1 mark)
Name a main heating system that cannot supply domestic hot water,
i.e. one where you cannot use Hot Water ―from main heating‖.
_______________________________________________________
Q6 (1 mark)
What insulation would you record for a pre-encapsulated cylinder?
(a) None
(b) 50mm spray foam
(c) 50mm jacket
Q7 (1 mark)
When would you record the water heating type as ‗none‘?
(a) When there is no water heating system installed
(b) When the water heating system is not working
The answers to this self-test are on the next page.
Section 7 Self-test result: ____ / 10
RDSAP Manual March 2012
self-test answers
Q1
(a) Normal 90-130 litres
Q2
(b) Dual immersion
Q3 (a)
True
Q3 (b)
Hot water cylinder thermostat
Q4 (a)
True
Q4 (b)
False
Q4 (c)
True
Q4 (d)
True
Q5
Pick one from the list below:
1. Storage heaters
2. Room heaters without back boilers
3. Electric ceiling heating
Q6
(c) 50 mm spray foam
Q7
(a) When there is no water heating system installed
Section 7: Score:
RDSAP Manual March 2012
/10
RDSAP Manual March 2012
8.
RDSAP Manual March 2012
Section eight | Renewables
Renewables
introduction
Renewable energy is energy produced from natural resources such as
sunlight, wind, rain, geothermal heat, which are renewable (naturally
replenished.
The introduction of government initiatives to increase the number of
domestic renewable installations has led to these becoming more
common. RDSAP caters for wind turbines, photovoltaic panels and solar
thermal panels (for hot water).
The energy costs on the EPC do not include any benefit from microgeneration (wind or PV).
photovoltaic
panels
Solar electricity systems capture the sun's energy using PV cells. The
cells convert the sunlight into electricity, which can be used to run
household appliances and lighting. The panels are often mounted on the
roof but can also be located in other suitable positions. Each cell is
made from one or two layers of semiconducting material, usually
silicon. When light shines on the cell it creates an electric field across
the layers. The stronger the sunshine, the more electricity is produced.
PV cells come in a variety of shapes and colours, from grey solar tiles
that look like roof tiles to panels and transparent cells that you can use
on conservatories and glass.
The strength of a PV cell is measured in kilowatt peak (kWp). That is
the amount of energy the cell generates in full sunlight.
Above left: roof-mounted PV panels; above right: PV roof tiles.
In terms of recognition, PV roof panels may have a glassy surface, often
with a grid pattern of squares or diamonds. The owner will be keen to
tell you about this system and data about it may be found by the
electricity meter in the house. The panels may be located elsewhere,
such as in the garden; or if the house has PV roof tiles they may be less
RDSAP Manual March 2012
obvious.
If documentary evidence (there is normally information or a schematic
of the system, adjacent to the meter)of the kWp of the PV system is
available then the following information is required:
The kilo Watt peak (KWp) rating, which may be found on a data
panel, often located close to the electric meter.
The pitch of the PVs (horizontal, 30°, 45°, 60°, vertical). If in
doubt select 30°.
The orientation of the panel if it is not horizontal (N, NE, E, SE,
S, SW, W, NW). South facing PV will benefit from most direct
sunlight.
Any over-shading from trees or other buildings should be
selected from the software‘s options of none or very little,
modest, significant or heavy.
If the kWp of the system cannot be ascertained:
Enter an estimate of the percentage of the total roof area which
the array covers to the nearest 5%. Here the total roof area
includes the main roof and any extension roofs.
Multiple PV
systems
If there are PV panels on different planes of the roof, enter as different
systems. If a single kWp figure is provided, estimate the relative area of
each and apportion the kWp accordingly. Up to three different PV
systems can be entered.
RDSAP Manual March 2012
wind turbines
introduction
40% of all the wind in Europe blows over the UK, making it an ideal
country for small domestic turbines. Wind turbines harness the power of
the wind and use it to generate electricity. Small systems known as
micro-wind or small-wind turbines can produce electricity to help power
the lights and electrical appliances in a typical home.
Data entry
If there is documentary evidence of the hub height and rotor diameter
this can be entered into the software.
If the wind turbine details are known, up to five wind turbines with the
same specification can be entered.
If there are multiple wind turbines with varying hub heights or rotor
diameters, contact Technical Support who will provide a spreadsheet to
work out the equivalent data entry the multiple turbines.
The hub height is the height of the hub of the turbine above the roof
ridge line. The rotor diameter is the diameter of the area swept by the
rotor blades.
Left: wind turbine.
If there is no evidence of the specification of the wind turbine, tick the
‗has wind turbines‟ check box and the software will assume a default
system of 2 m hub height with 2 m rotor diameter.
Documentary evidence is required to overwrite default values for wind
turbines.
RDSAP Manual March 2012
Feed-in-tariff
The Feed-in-Tariff (FIT) is a government initiative introduced to help
increase the level of renewable energy in the UK. The FIT applies to
energy from Wind and PV that have been installed in accordance with
the Microgeneration Certification Scheme (MCS).
The recipient of the FIT is not always the owner of the house it is
installed on. Some companies will ‗Rent a roof‘, i.e., they will pay for
the system and benefit from the FIT payments, whilst the occupant
receives some free electricity. The recipient of the FIT will receive a
payment for every kWh of energy produced and also a payment for
every kWh exported (currently assumed to be 50%).
The FIT is only applicable in England & Wales and Scotland.
The FIT payments are not included in the SAP rating, nor the estimated
energy costs of the dwelling. Therefore if your survey includes PV or
wind you should add addenda 8:
“The assessment does not include any feed-in tariffs that may be
applicable to this property.”
Solar thermal panels
introduction
Solar water heating systems use free heat from the sun to warm
domestic hot water. A conventional boiler or immersion heater is then
used to make the water hotter, or to provide hot water when solar
energy is unavailable. Solar panels called collectors are usually fitted to
your roof. These collect heat from the sun and use it to warm water
which is stored in a hot water cylinder.
There are three types of solar water heating panels: evacuated tubes,
flat plate collectors and unglazed panels. Unglazed panels are less
efficient than evacuated tube or flat plate panels and are typically used
to heat water for swimming pools.
Above left: Evacuated tubes; above right: Flat plate collectors.
RDSAP Manual March 2012
With either type, a boiler or immersion heater can be used as a back up
to heat the water further in order for it to reach the temperature set by
the cylinders thermostat when the solar water heating system does not
reach that temperature. (The cylinder thermostat should be set at 60
degrees centigrade.)
Larger solar panels can also provide energy to heat your home as well,
though usually only in the summer months when home heating is
unnecessary. Despite the fact that the UK weather is unpredictable,
solar thermal systems can cut water heating bills significantly.
In terms of identification, solar thermal should not be confused with
photovoltaic systems (PV). The home owner will usually be keen to
tell you about the heating system and visually you may see water pipes
entering and leaving the panels. There will be a control unit somewhere
in the house, probably with the water cylinder.
Data Entry
The data entry for solar thermal panels can be divided into three
sections:
1. Roof information
Pitch
Orientation
Overshading
2. Solar panel details
Collector type
Area of the panel (s)
Zero loss efficiency
Heat loss coefficient
Solar circulating pump
3. Solar store details
Solar store combined
Dedicated solar volume
Total cylinder volume
RDSAP Manual March 2012
RDSAP Manual March 2012
Roof information The roof information can be entered from visual evidence, even if the
specification of the actual system is not known.
The pitch of the panels (horizontal, 30°, 45°, 60°, vertical).
The orientation of the panel if it is not horizontal (N, NE, E, SE,
S, SW, W, NW).
Any over-shading from trees or other buildings should be
selected from the software‘s options of none or very little,
modest, significant or heavy.
solar panel
details
Documentary evidence is required to overwrite the default solar panel
details. This information is often found on a specification sheet.
Collector type (unglazed, flat panel, evacuated tube).
Area of the panel (s) (between 0.5 m2 and 10 m2).
Zero loss efficiency (η0)–a measure of the proportion of
radiation falling on the panel that is absorbed. (Values between
0.3 and 0.9.)
Heat loss coefficient–a measure of the ability of a panel to retain
heat (values between 0.5 and 20.0 W/m2K).
Solar circulating pump (electrically powered, PV powered or
unknown).
solar store
details
If there is documentary evidence of the solar hot water store, this can
be entered. If details of the panel are known but not the store, enter
the panel details and default store details will be used in the calculation.
Solar store combined: is the dedicated solar hot water storage in
the same vessel as the domestic hot water?
Dedicated solar volume: the volume of the combined or separate
solar store (values between 0 and 500L).
Total cylinder volume: the volume of the hot water cylinder
(values between 100 and 1000L).
If no panel details are available tick solar water heating and the RDSAP
default values will be used for the calculation.
Documentary evidence is required to over-write collector or solar store
values except that orientation, tilt and overshading can be overwritten
with visual evidence.
RDSAP Manual March 2012
self-test: Section 8
Q1 (1 mark)
Which of the three solar panel collector types is likely to be uised to
heat water for a swimming pool?
(d) unglazed
(e) flat plate glazed
(f) evacuated tube
Q2 (2 marks)
Which of the following data items regarding solar panels can be
overwritten without documentary evidence?
(c) Orientation
(d) Area of solar panel(s)
(e) Solar circulating pump
(f) Overshading
(g) Zero loss collector efficiency
Q3 (1 mark)
How many different PV systems can be entered into RDSAP?
_______________________________________________________
Q4 (3 marks)
Answer true or false to the following statements
(e) Solar thermal hot water systems can only be entered into
RDSAP if there is documentary evidence of the specification
(f) Solar PV systems can only be entered into RDSAP if there is
documentary evidence of the specification
(g) Wind turbines can only be entered into RDSAP if there is
documentary evidence of the specification
Q5 (1 mark)
How would you estimate the size of a PV system if there were no
evidence of its output?
_______________________________________________________
RDSAP Manual March 2012
Q6 (1 mark)
What does FIT stand for?
_______________________________________________________
Q7 (2 marks)
What are the two items of data that can be entered into RDSAP when
the wind turbine specification is known?
_____________________________________________________
_____________________________________________________
The answers to this self-test can be found on the next page.
Section 8 Self-test result: ____ / 11
RDSAP Manual March 2012
Self test answers
Q1
(a) Unglazed
Q2
(a) orientation (d) overshading
Q3
Three
Q4
(a) false-a default system can be used if details are not known
(b) false-a default system can be used if details are not known
(c) false-a default system can be used if details are not known
Q5
Q6
Q7
Estimate and enter the % of the total roof area covered by PV panels.
Feed In Tariff–a government initiative that provided payments for energy
produced using micro-generation such as Wind or PV.
Hub height: the height of the hub of the turbine above the roof ridge line.
Rotor diameter: the diameter of the area swept out by the rotor blades.
Section 8: Score_____ / 11
RDSAP Manual March 2012
RDSAP Manual March 2012
Section nine | Recommendations
Recommendations
introduction
Recommendations are an important element of the EPC. One of the
main purposes for introducing the EPC was to assess where
improvements could be made and reduce running costs and carbon
dioxide emissions.
The recommendations produced by the RDSAP software for inclusion
in the EPC are selected from a standard set of energy efficiency
improvement measures available to residential dwellings. The EPC
displays the recommendation together with the potential SAP rating
and cost saving, if installed.
General criteria
Energy efficiency improvement measures become recommendations
for a particular dwelling if they fulfil the following criteria:
Are relevant to the property in question (i.e. cavity fill where
a cavity wall is present)
Produce the required increase in the SAP rating
The minimum SAP increase for each of the recommendations is in
most cases 1 SAP point, less for low energy lighting, draught
proofing and waste water heat recovery. The minimum SAP point
difference required is set in the product database and is changed
periodically. For this reason, recommendations which you might
expect to appear in the report sometimes do not.
The measures are applied in prescribed order, with fabric
improvements coming first. The savings calculated are cumulative,
so applying individual measures will get a different saving. For
example if the recommendations and savings on the EPC were:
Loft insulation £100
Heating controls £57
The heating controls saving is the saving AFTER insulating the loft, if
you suppressed the loft insulation recommendation, you will see
that the savings for the heating controls will change.
RDSAP Manual March 2012
Removing a
recommendation
from the EPC
A recommendation should not be suppressed unless there is
evidence, visual or documentary, showing that a specific
recommendation is not appropriate. For example a letter from
English Heritage stating that double glazing is prohibited as part of
the listing.
A listed building or property in a conservation area is not sufficient
grounds in its own right to suppress a recommendation.
If a recommendation is removed, this must be recorded in the site
notes, together with the evidence.
As the EPC lasts for 10 years, it is important to leave
recommendations in whenever possible. It may be that a
recommendation that is not appropriate now, may become so in the
future.
Unknown vs.
As-built
Entering a building element as insulation unknown or no access will
also have the effect of suppressing any recommendation for further
insulation. For example, using pitched roof–no access will prevent
any recommendation being made on the EPC, as no inspection of
the roof space has been made to ascertain suitability. There may
already be insulation present in sufficient depth. This applies to
insulation recorded as unknown for walls/floors/roofs and roof
rooms.
Unknown should only be used in exceptional circumstances e.g.
when there is conflicting evidence (inspection and/or documentary)
of added insulation whose presence cannot be ascertained
conclusively. If there is no evidence to suggest a cavity wall has
been insulated, do not use unknown–use As-built and allow the
recommendation to be made.
RDSAP Manual March 2012
The recommendations
The recommendations are applied in the order described here; they
can also be accessed in their entirety in Appendix T of the SAP 2009
Specification document.
Note that the savings associated with each measure are cumulative.
The savings associated with a boiler replacement assume the
preceding insulation measures have already been installed.
Loft insulation
This refers to increasing the depth of insulation at joist level.
Loft insulation will be assessed by the software if the main
property or any extensions have a pitched roof (not
thatched) with an accessible loft space and insulation at joist
level. If the insulation thickness is less than or equal to
150 mm or the entered U-value is greater than 0.35, the
recommendation is to increase the insulation at joists to a
thickness of 270 mm, provided that this makes the requisite
SAP point increase.
Note that the specification for the measure in the calculation engine
is to increase to 250 mm, as there is no RDSAP option for 270 mm
The EPC states 270 mm as this is the accepted best practice.
Entering insulation as ‗unknown‟ will suppress the
recommendation.
Entering the roof construction as „pitch, no access‟ will
suppress the recommendation.
Most insulation benefit is gained from the first 150 mm of the
insulation; adding more may not always make much difference to
the rating, so this recommendation may not always appear where
you might expect.
Rafter insulation
There is no recommendation for insulating, or upgrading existing
insulation at rafters.
RDSAP Manual March 2012
Flat roof
Insulation can be retro-fitted to either the inside or outside of a flat
roof. Flat roofs often need replacing and this is a good opportunity
to add insulation.
If the property has a flat roof with less than 100 mm of
insulation or a U-value greater than 0.5 (entered or
assumed) the impact of insulating the flat roof to a U-value
of 0.18 will be assessed.
A flat roof with As-built insulation in age bands A-F
(pre-1983) will have an assumed U-value greater
than 0.5.
Entering insulation as ‗unknown‟ will suppress the
recommendation.
Room in roof
insulation
This recommendation refers to insulating all parts of a roof room,
including the flat ceiling.
If the property has a roof room with any part
(slope/stud/gable/flat ceiling) having less than 100 mm of
insulation or a U-value greater than 0.5* (entered or
assumed) the impact of insulating all parts of the roof rooms
to a U-value of 0.25 will be assessed.
A roof room with As-built insulation in age bands A-F
(pre-1983) will have an assumed U-value greater
than 0.5.
Entering the insulation as „unknown‟ will suppress the
recommendation.
Cavity wall
insulation
Cavity wall insulation involves drilling small holes in the external
brick work and pumping insulation into the cavity:
The impact of cavity wall insulation will be assessed where
there are unfilled cavity walls with a U-value greater than
0.6* (entered or assumed).
An As-built cavity wall in age bands A-F (pre 1983)
has a U-value greater than 0.6.
RDSAP Manual March 2012
RDSAP Manual March 2012
RDSAP assumes that cavity walls built after 1983 were
constructed with insulation already within the cavity.
The energy assessor must have entered the wall insulation as
‗As–built‟ for the recommendation to be generated. Using
‗unknown‟ will have the effect of suppressing any
recommendation.
The measure will assess the impact of ‗filling the cavity‘, the
U-value of the improved wall will range from 0.50 to 0.35
depending on the age of the wall
Some cavity walls are not suitable for standard cavity fill insulation
Hard to treat cavity
and may require specialist treatment that may be more expensive.
walls
Also, some stone walls and system build walls could be suitable for
cavity fill. RDSAP does not recommend cavity fill for stone or system
built walls, but addenda are automatically added to the EPC if uninsulated stone or system built walls are identified. If there is a
cavity fill recommendation an addendum can be added to the EPC to
pre-warn that the cavity fill may not be straightforward should be
added.
These ‗tick box‘ options are available on the Results page on EPC
online.
Access issues: would there be problems for an installer reaching
the walls of the upper storeys, such as a conservatory or narrow
passage? If there are, the ‗Property has access issues‘ should be
ticked.
High exposure: is the dwelling in Zone 3 or 4 (the blue and green
areas) of the exposure map. If so, tick the ‗Property has high
exposure‘ box. If in doubt record as high exposure.
RDSAP Manual March 2012
Narrow cavities: a narrow cavity is a cavity less than 50 mm wide.
They are indicated by a stretcher bond brick pattern and wall
thickness of 220-250 mm. If you wall ‗may‘ have narrow cavities
tick the „Property has narrow cavities‟ to add an appropriate
addendum.
The table shows when the ‗tick boxes‘ are available and the wall
further assessed.
Wall
System build with insulation
Age band
A-F
‗As-built‘ or ‗unknown
Stone walls with insulation
Addenda options
Access issues
High exposure
Access issues
A-F
‗As-built‘ or ‗unknown
Narrow cavities
High exposure
Access issues*
Cavity
A-J
Narrow cavities*
High exposure*
*if there is a cavity fill recommendation
RDSAP Manual March 2012
Solid wall
insulation
Solid wall insulation refers to either internal insulation or external
insulation. The measure is only assessed for solid brick or stone
walls that are ‗As-built‘.
The impact of solid insulation will be assessed where there
are As-built stone or brick walls with a U-value greater than
0.6 (entered or assumed).
An As-built solid brick wall in age bands A-F (pre1983) has a U-value greater than 0.6. The U-value
of stone walls is dependent on the thickness of the
wall, so you could find a very old (but thick) stone
wall has no recommendation for insulation.
The energy assessor must have entered the wall insulation as
‗As–built‟ for the recommendation to be generated. Using
‗unknown‟ will have the effect of suppressing any
recommendation.
The measure will assess the impact of insulating to the wall to
achieve a U-value of 0.30.
Floor insulation
Insulation can be retro-fitted to floors, for suspended wooden floors
this can be relatively simple, by laying insulation between the joists.
The measure applies to ground floors and exposed upper floors
(exposed floor and semi-exposed to unheated space).
Note there is no floor insulation measure for semi-exposed floors to
partially heated spaces.
If the property has a ground floor (As-built) in age bands A-J
(pre 2007) the impact of adding 150 mm of insulation will be
assessed.
If the property has an exposed floor or semi-exposed floor to
an unheated space the impact of adding retro fit insulation
will be assessed (see SAP Appendix S Table S12 for the Uvalues of retro insulated exposed/semi exposed floors).
If the property has a ground floor with retro-fit insulation of
50 mm or an entered U-value greater than 0.5, the impact of
adding 150 mm will be assessed.
Entering insulation as ‗unknown‘ will suppress the recommendation.
RDSAP Manual March 2012
Cylinder insulation The software will recommend additional cylinder insulation as
described below, where the existing cylinder is accessible as follows:
No insulation present: install 80 mm jacket.
Spray foam insulation (factory applied), less than or equal to
25 mm–add 80 mm jacket.
Jacket insulation, less than 80 mm: add 80 mm jacket.
Note that if the cylinder has insulation that is poorly fitting
or partially missing, you should downgrade the thickness to
the point at which the software recommends a new jacket. In
addition to facilitating a new jacket the impaired function of
the insulation is better represented in the software.
Draught proofing
The impact of draught proofing is assessed where less than 100% of
the windows and doors are draught proofed.
Low energy lights
Where the existing proportion of low energy lights in the dwelling is
less than 100%, the impact of increasing this proportion to 100%
will be assessed.
Cylinder thermostat Where there is a hot water cylinder that is present and accessible
but has no cylinder thermostat, the impact of adding a cylinder
thermostat will be assessed.
Note that for electric immersion heaters, the software automatically
assumes that a cylinder thermostat is present. Immersion heaters
are equipped with thermostats within the appliance itself, adjustable
but usually factory set to 600 C.
RDSAP Manual March 2012
Heating controls
for wet central
heating systems
A wet central heating system is one supplying heat to radiators or a
wet underfloor system such as boilers, micro-CHP and heat pumps.
If the main heating is a boiler or micro-CHP supplying
radiators and the controls are anything less than
‗programmer, room thermostat and TRVs‘, then upgrading to
these controls will be assessed.
If the main heating is a boiler or micro-CHP supplying
radiators and the controls are ‗programmer, room thermostat
and TRVs‘, the impact of upgrading to ‗time and temperature
control‘ will be assessed.
If the main heating is a boiler of micro-CHP supplying heat
via a wet underfloor system and the controls are anything
other than ‗time and temperature control‘, then the impact of
upgrading to ‗time and temperature control‘ will be assessed.
If the main heating is from a heat pump (radiators or
underfloor) and the controls are anything other than ‗time
and temperature control‘, then the impact of upgrading to
‗time and temperature control‘ will be assessed.
Heating controls
for warm air
systems
Install biomass
boiler
Install biomass
room heater with
back boiler
Where the main heating is by mains gas or LPG warm air systems
(including heat pumps), the impact of upgrading to ‗programmer
and room stat‘ control will be assessed and recommended.
Where the existing main heating is by an independent solid fuel
boiler that is not biomass or dual fuel and mains gas is not available,
the impact of installing a manual feed biomass boiler (wood logs),
HETAS approved.
Where the existing main heating is by a solid fuel open fire or solid
fuel room heater (with or without back boiler) and is not biomass or
dual fuel and mains gas is not available, the impact of installing a
HETAS approved wood pellet stove with radiator and water heating
(with summer immersion heater) will be assessed and
recommended accordingly.
RDSAP Manual March 2012
Upgrade boiler—
same fuel
Where the main heating is by a mains gas boiler (including range
cooker boiler) or CPSU, or by an LPG or oil boiler (including range
cooker boiler) and mains gas is not available, the impact of
upgrading the boiler will be assessed as follows:
Existing boiler to a condensing boiler. Recommended boiler
will be either standard or combination boiler, depending on
whether a cylinder is present.
Non-condensing CPSU upgraded to condensing CPSU.
Range cooker boiler upgraded to either standard boiler or
combi boiler, depending on presence of existing cylinder.
The specification for the boilers is held in the Products
Database (PCDF) and may be updated periodically.
Condensing oil
boiler
Gas condensing
boiler installation
(no fuel switch)
If the main heating is currently from an oil warm air system and
mains gas is not available, the impact of upgrading to a condensing
oil boiler will be assessed. The boiler will be standard or combi
depending on the presence of an existing cylinder.
Where existing main heating is by mains gas fires, the impact of
installing a mains gas condensing boiler with radiator heating will be
assessed and recommended accordingly. Recommended boiler will
be either standard or combination boiler depending on whether
there is a cylinder present.
RDSAP Manual March 2012
Gas condensing
boiler installation
Where existing main heating is by one of the following:
Solid fuel boiler
LPG boiler
LPG fires
Oil boiler (non-condensing)
incorporating fuel
switch to mains
gas
Oil warm air
Solid fuel room heaters
Electric storage heaters
Electric under floor heating
Electric room heaters
Electric ceiling heating
No space heating system present
And mains gas is available; the impact of installing a condensing
mains gas boiler to radiator heating will be assessed and
recommended accordingly. Recommended boiler will be either
standard or combination boiler, depending on whether there is a
cylinder present.
Note that where the original system is off-peak, storage heaters or
electric underfloor, the measure includes changing the meter to a
single tariff.
FGHRS
Installing new or
replacement
storage heaters
Where there has been a recommendation for a new condensing gas
boiler (mains gas or LPG), the impact of also installing a flue gas
heat recovery system will be assessed.
Where the existing main heating is by storage heaters other than
fan-assisted storage heaters, or by electric room heaters or electric
ceiling heating and mains gas is not available, the impact of
installing fan assisted storage heaters with automatic charge control
is assessed and recommended accordingly.
Where the water heating is via a single immersion or from solid fuel
secondary heating, this is also upgraded to a large pre-insulated (50
mm spray foam) dual immersion hot water cylinder as part of this
assessment.
If there is no secondary heating present, then on-peak electric
heating is assumed as secondary heating as part of this assessment.
RDSAP Manual March 2012
Upgrade warm air
unit
Where the existing main heating is by mains gas or LPG warm air
and the system is pre-1998, the impact of installing a new (noncondensing) warm air unit (same fuel as original) is assessed and
recommended accordingly.
Solar water heating Where the dwelling in question is a house or bungalow and there is
no existing solar water heating present, the impact of installing a
3m2 solar water heating system will be assessed and recommended
accordingly.
This does not apply for dwellings with thatched roofs.
WWHRS
Where the dwelling has at least one mixer shower and no waste
water heat recovery, the impact of installing a WWHRS will be
assessed.
Double-glazing
Where the existing proportion of windows that is multiple-glazed is
less than 80%, the impact of replacing existing single-glazed
windows with double-glazing will be assessed and recommended
accordingly.
The specification for the double glazing is U-value 1.5 and
g-value 0.63.
Secondary glazing
Where double-glazing has been recommended as above but deselected by the assessor, the secondary glazing of existing singleglazed windows will be assessed and recommended accordingly as
an alternative.
Insulated doors
Where there is a flat/maisonette with no corridor or a
house/bungalow with any un-insulated doors directly to the outside,
the impact of changing the doors to insulated doors with a U-value
of 1.5 is assessed.
For flats and maisonettes with a corridor there must be more than
one door for the measure to be assessed. This is to avoid
recommending an insulated door to a corridor, which is already
sheltered.
RDSAP Manual March 2012
Photovoltaics
Where the existing dwelling is a house or bungalow, which does not
have a photovoltaic system, or which has a PV array of less than
1kW at peak output, then the impact of installing a 2.5 kWp PV
system will be assessed and recommended accordingly. This
recommendation does not apply to dwellings with thatched roofs.
Wind turbine
Where the existing dwelling is a house or bungalow, which does not
have a wind turbine, the impact of installing a micro wind turbine
will be assessed and recommended accordingly. The wind turbine
measure has a 2m hub height and 2m rotor diameter.
Alternative measures
introduction
Alternative measures are a set of additional measures that do not
appear in the main recommendations list. There are no savings
displayed, but the measure must make at least a £10 to appear on
the EPC.
The purpose of these alternative measures is to advice the
householder that there are other measures that they could consider
which would improve the energy efficiency of their home.
External wall
insulation with
cavity fill
When there is a recommendation for cavity wall insulation,
this additional measure is also assessed.
The cavity wall insulation measure ‗fills the cavity‘. The
associated U-value used in the calculation is taken from table
S6 (E&W) and is dependent on the age band. The assumed
U-values for a filled cavity in RDSAP range from 0.50-0.30.
The alternative measure assesses the impact, after applying
the cavity fill, of changing the wall U-value to 0.30.
If the impact produces a saving of more than £10, external
insulation with cavity insulation will appear on the EPC in the
Alternative measures section.
RDSAP Manual March 2012
Biomass boiler
This will be assessed if both the following criteria are met:
o The original heating is not solid fuel or community
o There is a heating system recommendation
The improvement is to a wood logs boiler with the
specification from the Product Database (PCDF).
This is the same as improvement ‗J-biomass boiler‘ and this
is why it is not assessed as an alternative measure if the
original heating is solid fuel. It will have been assessed
already.
If the impact produces a saving of more than £10, biomass
boiler will appear on the EPC in the Alternative measures
section
Heat pump
This will be assessed if both the following criteria are met :
o The original heating is not a heat pump or community or
a wet underfloor system
o There is a heating system recommendation
The improvement is to an air source heat pump (ASHP) with
radiators and the specification from the Product Database
(PCDF).
The alternative measure is displayed on the EPC as ‗air or
ground source heat pump‘. As the efficiency of a ground
source heat pump will be higher than an ASHP the impact is
assessed using an ASHP.
If the impact produces a saving of more than £10, heat pump
will appear on the EPC in the Alternative measures section.
Heat pump with
underfloor heating
This will be assessed if both the following criteria are met :
The original heating is not a heat pump or community:
o and there is a wet underfloor system and the heat
pump (radiators) alternative measure does not apply
o There is a heating system recommendation
The improvement is to an air source heat pump (ASHP)with
underfloor heating and the specification from the Product
Database (PCDF).
The efficiency of a heat pump is higher with underfloor
heating as the flow temperature can be lower.
If the impact produces a saving of more than £10, heat pump
RDSAP Manual March 2012
with underfloor heating will appear on the EPC in the
Alternative measures section.
micro-CHP
This will be assessed if both the following criteria are met :
o The original heating is not from micro-CHP or
community
o There is a heating system recommendation
The improvement is to a mains gas Micro-CHP unit with the
specification from the Product Database (PCDF).
Mains gas does not need to be present for this measure to be
assessed.
If the impact produces a saving of more than £10, micro-CHP
will appear on the EPC in the Alternative measures section.
Green deal
introduction
Golden rule
The RDSAP EPC will be used to flag to which recommendations on
the EPC will be eligible for Green Deal finance. This will be indicated
by a tick (or lack of) next to the recommendation.
The Green Deal finance assessment is based upon meeting the
Golden Rule. The Golden Rule calculation uses the estimated
savings, life time and indicative cost of the measure to calculate if
the annual savings are more than the annual repayment over the
lifetime of the measure. If the annual savings are greater than the
annual repayment, the Golden Rule has been met.
Green tick
If the Golden Rule has been met, the recommendation will have a
green tick next to it. The only exception to this is Solid Wall
insulation. There will be grants available via the Energy Companies
Obligation (ECO) for solid wall insulation, so whenever this
RDSAP Manual March 2012
recommendation appears, it always has a green tick.
Orange tick
If the measure is available with the Green Deal but has not met the
Golden Rule, an orange tick will be displayed. This means the Green
Deal can be used to finance some of the cost of the measure, but
additional finance will be required. This could be the householders
own finance, or a grant may be available.
no tick
If the measure is not available with the Green Deal there will be no
tick. The only RDSAP measure that this currently applies to is low
energy lighting.
Green deal package All of the measures that have a green tick are combined to form the
Green Deal Package.
RDSAP Manual March 2012
RDSAP Manual March 2012
RDSAP Manual March 2012