Ventilation in
historic buildings
CONTENTS
s. 2 Foreword
3 Ventilation history, domestic buildings
6 Ventilation history, non- domestic buildings
9 Swedish regulations regarding ventilation
12 Swedish legislative protection for historic buildings
14 Ventilation principles
16 Good advice
23 Eight examples in Sweden:
24 1. Amiralitetshuset, Skeppsholmen, Stockholm
29 2. Sjöreservens kasern, Skeppsholmen, Stockholm
32 3. Dekanhuset, Uppsala
36 4. Gamla gymnasiet, Karlstad
42 5. Ladugården, Biskops Arnö
46 6. Landshövdingens stall, Uppsala
49 7. Södra Banco, Gamla Stan, Stockholm
54 8. Thielska galleriet, Djurgården, Stockholm
58 Glossary
Ventilation in historic buildings
The building is unique and the art at
Thielska galleriet, ­on Djurgården in
Stockholm, requires a certain climate to
prevent damage. The ambition has been
to maintain the old ventilation system
and complement it with installations
that do not affect the architecture of the
building.
1 ( 60)
Foreword
Ventilation in a building is a fundamental function. Preserving a culturally historic and valuable environment at the same time as providing
accepta­ble ventilation for the tenant requires a
great deal of experience and knowledge. This document has been drawn up to compile and share
the knowledge regarding ventilation in historic
buildings, which is currently held by the National
Property Board Sweden (SFV). This knowledge is
exemplified by general chapters on the history of
ventilation, provisions and legislative protection,
ventilation principles and good advice on main-
tenance and the design stage. In addition, eight
examples are presented of venti­lation solutions
implemented in historically valuable environments.
Through common understanding and competence improvement measures, SFV´s internal work
with maintenance and renovation of culturally
historical valuable buildings is facilitated and
made more effective. These guidelines shall be
able to function as a tool and inspiration for SFV
as a property manager and building owner and for
those consultants that SFV engages.
In preparing this document we have had the
support of a reference group compiled of property
managers, technical and operational managers
and building conservation officers within SFV ­
as well as the cultural heritage unit with all its
specialist competences.
Property managers, project managers, and
­operation technicians have contributed with
factual documentation and experiences from reference objects. In addition, consulting engineer
HVAC, Göran Stålbom, has parti­cipated in the
chapter Swedish regulations regarding ventilation
and the chapter Ventilation history.
Stockholm, 20090429
Carl Gösta Hellgren, HVAC specialist, SFV
Helena Adolphson, architect
Ventilation – a conservation concern!
In modern times, ventilation has often only been
seen as a technical function. The effort to create
the perfect indoor climate, which will function
with a minimum of effort by the users, has led to
increasingly bulky installations and technically
complicated systems. Making use of the design of
the building, which is a part of the ventilation system in historic buildings, has been neglected.
The original ventilation system is not only a
function but also an expression of the building’s
authenticity and character worthy of preservation.
Stairway with heating column in the Gamla riksarkivet on
Riddarholmen in Stockholm.
Ventilation in historic buildings
2 ( 60)
Ventilation history
Domestic buildings
Open fireplaces
Ventilation and heating are often connected.
Fires in ovens, tiled stoves and iron stoves create
negative pressure in the building and an upward
air stream in the flue – the stack effect. Replacement air is drawn in through leaks in walls, doors
and windows and creates background ventilation.
The hearth and its smoke flues have therefore,
in older times, been sufficient during the winter
to create the natural ventilation that is required.
With open fireplaces and unsealed windows and
doors, draughts were the major problem, not
the actual ventilation. During summer, when the
buildings were not heated by fire, the stack effect
decreased. Ventilation was then done by opening
windows.
In the 1700s and 1800s, windows were fitted
with fixed inner casements in the winter. One pane
in every room was able to be opened; a moveable
pane. When coupled window casements were
introduced at the end of the 1800s, the windows
were often designed with transoms and separate
upper casements for ventilation.
In order to improve the stack effect it was possible to fit chimneys with a cowl. It moves according to wind direction and
creates negative ­pressure in the flue.
Ventilation in historic buildings
Moveable panes in both the outer and inner window casement. By making a small casement within the casement you
could easily obtain ventilation without needing to open the
entire window. Oxenstiernska palatset.
3 ( 60)
Radiator heat and stack ventilation
From the 1920s, new buildings had radiator
systems and bathrooms. Older buildings were
restored with bathrooms and central heating.­
At this time, the majority of buildings were deep,
as opposed to the narrow buildings that were
­constructed later on with modernism. Therefore,
bathrooms were situated in the dark cores of
the buildings. To ventilate these, a form of stack
ventilation, so called Stockholm ventilation, was
developed. The principle is that the bathroom has
separate ducts for intake air and exhaust air. The
air from the bathroom rises thermally, due to the
stack effect, out through exhaust air vents near
the ceiling via a brick flue in a chimney and out
of the building. The intake air (replacement air)
is drawn from the ground floor on the shady side
of the building into the bathroom via a duct or a
brick flue. In the winter, the stack effect is easiest
to achieve, but this form of ventilation also works
in the summer. During summer, the top of flue
in the chimney stack is warmer than the duct for
the intake air on the shady side of the building.
This creates negative pressure in the flue, which
speeds up the air flow out of the building and cool
replacement air is drawn into the bathroom. The
From the 1920s, open fires were replaced by radiator systems
with radiators below the windows. Areas near the external
walls, which had previously been draughty and cold and had
been used as passageways, now became warmer and were
used as social areas. For intake air via windows, people have
to be aware when placing furniture that there is a risk for
draughts in areas close to the windows, even if it is heated.
Oxenstiernska palatset, Stockholm.
Ventilation in historic buildings
Flap vent from Ahsell
& Bernström’s catalogue no. 32. This
type of vent located
in the external wall
was often used during the 1800s and
early 1900s to take in
outside air.
Disc valve Disco from
Rylander & Asplund’s
catalogue no. 36.
Commonly used as an
intake vent in so-called
Stockholm ventilation.
4 ( 60)
apartment’s kitchens and living areas had their
own exhaust air flues and intake air via windows
and vents in the external walls.
Low pressure systems
In the 1930s, ceiling heights were reduced at the
same time that fan ventilation was established.
These early exhaust air systems existed parallel
with stack ventilation up to the 1960s. The air was
normally drawn in through slotted vents below
windows. In 1931, the so-called overflow method
was launched and has been used since then. This
involves the air streaming in the “right way”: from
bedrooms and the living room to the bathroom
and kitchen. In that way a more efficient use of air
was achieved. The ducts were often constructed
of sheet metal but could also be made of mortar,
concrete or asbestos cement. After the 1960s,
sheet metal ducts dominated.
Controlled ventilation
Older fan systems had axial fans and disc valves
with low pressure. In the early 1940´s, Svenska
fläktfabriken launched a system with radial fans
with higher pressure and so-called control valves
that made possible a higher fall of pressure without sound problems. The advantage was that the
ductwork could be made simpler and you could
­adjust the airflow with a higher degree of precision. The outside air was drawn in via slotted
vents beneath windows.
Supply and exhaust air systems
Systems with both supply air and exhaust air were
installed in a number of apartment buildings in
the early 1970s. However, it was first with the energy provisions of the 1975 and 1980, a result of
the oil crisis in the 1970s, that this had an impact.
Through the supply and exhaust air systems with
heat exchange the standard requirements for heat
recovery could easily be attained. But as early as
the 1980s there were objections to the systems
Ventilation in historic buildings
Slotted vents beneath a window seat; common from the 1930´s.
Control valve KGD with attachment frame. From Svenska
fläktfabriken’s Catalogue from 1963.
(based on maintenance problems and high operating costs), and a search for alternatives started.
Return to the exhaust air system
At the end of the 1980s, it was recommended by
housing companies to only use exhaust air
systems in newly constructed housing. For recovery, a heat pump was used to heat hot water.
Intake-air radiators, where the air was filtered and
pre-heated, were often used for intake air.
5 ( 60)
Ventilation history
Non-domestic buildings
Open fireplaces
Offices, schools, hospitals, etc., were heated and
ventilated in ways similar to residential housing.
In prisons and mental institutions a central heating system was desired to avoid dealing with fire
in the premises.
Iron stove ventilation
In the 1860s a new system for ventilation was
launched where the driving forces of the fireplace
was utilized to get pre-heated air and increased
ventilation. The manufacturers marketed special
iron stoves and tiled stoves for this purpose.
Cool outdoor air was conveyed from an insulated
duct and let in at the bottom of the iron stove.
The air was warmed and let out the top of the iron
stove. The room’s exhaust air vent, located near
the floor, was connected to a flue that ran next to
the smoke flue. In this way, the exhaust air flue
was heated for efficient air-flow.
Calorifère systems
Calorifère systems made their appearance in the
latter part of the 1800s up through around 1910.
They were central systems for both ventilation and
heating and primarily used in school buildings,
churches, barracks and hospitals. The outdoor air
was drawn into a heat chamber in the cellar and
then forwarded through separate ducts to each
room. Sometimes the Calorifère systems had a
complicated network of mortared ducts in order
to make possible different oper­ation scenarios.
When central heating, in the form of radiator
systems from the 1920s, became a standard solution for new construction, the Calorifère systems
Before radiators were introduced in the form that we are now
familiar with, they were designed in different styles. Here in
Gamla riksarkivet on Riddarholmen they are designed as columns. In addition, some of these columns were provided with
external air, conveyed via the joisted floors into the bottom
of the radiator. The heated air rose upward and out the top of
the radiator. Gamla riks­arkivet, Stockholm
Ventilation in historic buildings
6 ( 60)
disappeared along with their double function for
heating and ventilation. Individual Calorifère systems can still be found, for example, in Thielska
galleriet on Djurgården. They can also be found in
new constructions with systems with heat chambers for the warming of intake air for example in
Ladugården, Biskops Arnö and the exhibition pavilion at Birka.
Radiator heating and stack ventilation
When central heating became predominant,
exhaust air ventilation was solved with the help
of the stack effect in brick flues. Intake air was
drawn in via flap-vents in the external walls and
through leaks in doors and windows.
Low pressure systems and early supply and
exhaust air systems
In the 1930s, a system was developed with separate supply and exhaust air ducts. Supply air
devices were often located in the false ceiling in
the middle of office spaces or in the “back corner” by the ceiling in the wall facing the corridor.
There was also a system where the air was supplied through a perforated false ceiling. From the
1960s, the system with supply air became much
more common in offices, schools, etc.
Climate systems
After 1975, climate systems were often provided
with comfort cooling. The function of the systems
was to remove surplus heat. Sometimes the heating system was integrated into the ventilation
system; heating was done using air. The systems
became increasingly advanced. One system that
was developed in the 1960s was the dual-duct
system: two supply air systems distributed air at
different temperatures and the air was mixed to
a suitable blast air injection temperature in each
room. During the 1980s, the low-flow system with
fan convectors (fan coils) placed in rooms became
common. ­During the 1990s, the cooling-baffle
(chilled beam) system was developed, first as
Ventilation in historic buildings
Thielska galleriet, in Stockholm, has an original Calorifère system. The radiators in the heat chamber pre-heat the intake air.
These fan convectors, so-called fan coils, have a single fan
assisted batteries providing either chilled or heated air, as
­required by the room temperature controls.
7 ( 60)
separate cooling batteries with their own convection, but relatively soon as integrated devices with
both cooling batteries and supply air devices. In
the early 2000s, interest for Variable Air Volume
(VAV) systems has increased, in other words, systems that utilize a varying air flow to govern the
cooling effect.
Cooling baffles located near the ceiling. The air is cooled and
falls down into the room.
Simpler systems
At the end of the 1980s, protests were raised by
those who considered that the systems had become increasingly space intensive and complex.
A return to simpler systems was proposed and
from the end of the 1990s a great many systems
were installed that combined stack ventilation
and fan ventilation, so-called hybrid ventilation.
Solutions with automatic window opening systems were also tested.
As an alternative or complement to stack ventilation there are
automatic window opening systems. These are computer-controlled and regulated based on ventilation needs. Vaxholms kastell.
Ventilation in historic buildings
8 ( 60)
Swedish regulations regarding ventilation
Building legislation
All construction is governed by building legislation. For new construction there are detailed provisions in the Building regulations (BBR) formulated by the National Board of Housing, Building and
Planning (Boverket). For alterations (renovations)
there are no provisions. The alteration recommendations (BÄR), formulated by Boverket, only contain general recommendations. BÄR emphasizes a
“careful comprehensive view” and leaves openings for ventilation solutions other than those required by BBR. In works to older buildings it is
wrong to routinely comply with BBR.
As a complement to the provisions, Boverket
gives guidelines in the handbook Stack ventilation
from 1994 and the Swedish Building Centre (Svensk
Differences between provisions and general recommendations
The Swedish Parliament
Laws
The Government
Ordinances
Central
government
authorities
Provisions
Statutes
Mandatory
Issued by:
Regulations
Requirement or recommendation?
Society makes requirements through laws, ordinances and provisions. The professional primarily
comes into contact with provisions and general
recommendations, in which the authorities have
clarified the legal requirements.
The provisions are mandatory, but the requirements are often formulated in words as “necessary air exchange”, “good air quality” and
“sufficient airflow”. As guidelines for the regulations, the authorities therefore issue general
recommendations and handbooks with specific
values. The general recommendations provide
recommendations about what you can or should
do, but naturally do not exclude other measures.
In individual cases an individual professional assessment must be made of what the provisions´
requirements on air exchange, air quality and
comfort actually entail in practice.
Not mandatory
What laws apply?
The Planning and Building Act (PBL) and the
Act on Technical Requirements for Construction
Works (BVL) are usually jointly referred to as
building legislation. They apply to all construction. Requirements are normally made on the
property owner and apply to the building’s technical characteristics.
The Environmental Code and Work Environment
Act place no requirements on the actual building.
Instead, requirements are placed on the environment or work environment, which exists in the
building. The requirements are primarily directed
towards “persons operating a business” and the
“employer”, normally the tenant. However, certain
requirements are directed towards the property
owner.
The laws make demands on ventilation, but
this does not mean that you can carry out any
measures or additions you wish. PBL requires
that care shall be taken in the alteration of all
buildings. The Environmental Code requires that
valuable cultural environments are protected and
preserved. Certain buildings are also protected ­
by the Heritage Conservation Act.
Therefore, in every individual case a solution
must be found that fulfils both the requirements
for ventilation and the requirements for the preservation of cultural value.
General recommendations
Source: Göran Stålbom
Ventilation in historic buildings
9 ( 60)
byggtjänst) publishes Construction guidelines 15 –
Renovation, 2000 and Construction guidelines 7 –
Ventilation, 2008. Here, there are a number of
guidelines regarding stack ventilation and fanassisted stack ventilation.
For building alterations, BÄR applies. For on­
going management you go directly to BVL, which
says that facilities for ventilation shall “be maintained”. To ensure that this is done, this is regularly
checked through function inspections of the ventilation system, (OVK). The professional assessment in individual cases is thus the responsibility
of the function inspector.
Function inspection of ventilation
systems (OVK)
The ordinance regarding function inspections
(1991:1273) shall ensure that all buildings, both
new and old, shall have a satisfactory indoor
­climate.
The function inspection shall occur before a
new ventilation system is put into operation the
first time (first inspection). Existing systems shall
be inspected regularly in accordance with the
­prescribed time interval.
Work Environment Act
The requirements in the Work Environment Act
primarily relate to workplaces and schools. ­
The Swedish Work Environment Authority issues
regulations and general recommendations in
order to clarify the requirements, and regulations
regarding ventilation can be found mainly in Workplace design (Arbetsplatsens utformning – AFS
2000:42). In these general recommendations
there are several guidelines for air exchange.
It is often difficult to complement older buildings with the same type of fan ventilation as new
buildings. Therefore, there is a special provision
Skridskopaviljongen at Kastellholmen in Stockholm is being
converted into a conference facility and is getting a ventilation system that is adapted to the building’s historic value.
Ventilation in historic buildings
10 ( 60)
for “older buildings with historic value” in AFS
2000:42. It states, among other things that:
To avoid unnecessary measures to the building,
special care should be given to the selection of
technical solutions in the application of the provisions. When measures are necessary in order
to achieve an acceptable work environment a
measure should be chosen that involves the
least possible damage to the historic value.
Therefore, in individual cases, a thorough balance
must be made. As an alternative to increased air
flow, for example, the general recommendations
state “shorter work sessions with intermittent
opening of windows”.
Environmental Code
The Environmental Code mainly applies to
residences, preschools and premises where the
public has access. The Environmental Code’s requirement for ventilation is primarily detailed in
the general recommendations that are issued by
the National Board of Health and Welfare. There
you can find guidelines for air exchange (similar
to those of the Work Environment Authority). But
the recommendations also emphasize ventilation
possibilities, length of stay and procedures for
ventilation.
The National Board of Health and Welfare’s
general recommendations call for a comprehensive assessment of the conditions of the buildings or premises for the operation concerned.
The National Board of Health and Welfare does
not state anything about buildings of cultural
value, but one of the principles in the Environmental Code is the protection and preservation
of valuable natural and cultural environments.
The Environmental Code’s requirement for
­protection and preservation of valuable cultural
environments shall be assessed on a case by case
basis in accordance with its requirements for indoor environments.
Ventilation in historic buildings
The official residences, “Långa raden”, on Skeppsholmen in
Stockholm, originally built as barracks for Karl XII’s bodyguards, is now being renovated into a hotel. A modern ventilation system adapted to the building is being installed.
Laws
•
•
•
•
•
Planning and Building Act (PBL).
Act on Technical Requirements for Construction Works (BVL).
Work Environment Act.
Environmental code.
Heritage Conservation Act.
Other regulations and regulatory frameworks
•
•
•
•
General recommendations regarding alterations
to buildings, BÄR, the National Board of Housing, Building and Planning, 2006.
Regulations for function inspections of ventilation systems, OVK, the National Board of
Housing, Building and Planning, 2008.
Workplace design, Swedish Work Environment
Authority, 2000.
The National Board of Health and Welfare’s general recommendations regarding supervision in accordance with the Environmental code – ventilation, 1999.
11 ( 60)
Swedish legislative protection for historic buildings
Protected buildings and building areas
Buildings, parks and other facilities, land areas,
city centres and other cultural environments that
are a part of our Swedish cultural heritage are protected through a series of different provisions at
the governmental and municipal level. Those that
are particularly significant can become listed historic buildings. Buildings that are not significant
in themselves can also be included in this protection if the entire building area, where they are located, is classified as a conservation area.
Ordinance (1988:1229) regarding historic state-owned listed buildings, FSBM
The Government decides if a state-owned building shall be listed, SBM, after proposals from the
Swedish­National Heritage Board (RAÄ), which is
the super­visory authority that establishes protection orders for the building. A somewhat lower
protection class is valuable building and valuable
property in accordance with FSBM § 12–16. Consultation takes place with the Swedish National
Heritage Board for these in the case of measures
that may threaten the historic value.
Heritage Conservation Act (1988:950), KLM
Buildings of cultural-historical importance that are
not listed in accordance with FSBM may be listed
by the county administrative boards, which are
responsible for formulating protection orders for
the listed buildings in cooperation with the owner.
Chapter 2 of the KML legislation addresses questions regarding ancient and historic monuments
and sites. In many older cities, entire city centres
are designated as conservation areas where
measures may require authorization by the county
administrative boards.
Planning and Building Act (1987:10), PBL
The Planning and Building Act, chapter 3 § 10–12
states that all alter­ations to buildings should always be carried out carefully so that, for example,
architectonic and historic values are safeguarded.
Especially valuable buildings are protected in
­detailed plans and area provisions. The municipality is the supervisory authority in accordance
with the Planning and Building Act.
Environmental Code (1998:808), MB
The Environmental Code covers areas that are of
nationwide interest from a cultural perspective.
Major measures may require an Environmental
­Impact Assessment.
Protection orders and authorization
The protection orders for state-owned listed buildings, formulated by the Swedish National Heritage
Board and determined by the Government, define
the values that are protected. In the protection
orders it is stated what parts of the building that
are specially protected. Authorization always
must be obtained from the Swedish National
­Heritage Board for alterations that conflict with
protection orders before any alterations may be
made. Drilling in walls and joisted floors for ventilation ducts or the mounting of new fans on roofs
are examples of meaures that require authoriza-
Authorization from the Swedish National Heritage Board is
required for drilling in existing brickwork.
Skridskopaviljongen, Kastellholmen in Stockholm.
Ventilation in historic buildings
12 ( 60)
tion. Authorization for alterations to all other
­listed buildings must be obtained from the county
administrative boards.
Conservation plan
SFV has decided that every state-owned listed
building shall have its own conservation plan.
It describes the building’s value and SFV’s longterm goal for the conservation and development
of the building. The conservation plan gives
­recommendations and guidelines for the building’s future management.
There is no legislation requiring conservation
plans for other listed buildings. Nevertheless,
the county administrative boards actively work
to ensure that such plans are drawn up and grant
subsidies to property owners for this.
Installation projects
Consequently, for installation projects, measures
to protected parts must be approved by the
Swedish National Heritage Board or the county
administrative boards. Consideration must also
be given to the legal text in the Planning and
Building Act, which states that alterations shall
be carried out carefully so that the building’s
characteristics are taken into consideration. It
can be very useful to let a conservation officer do
a conservation assessment early in the design
stage.
Measures to building foundations, for example
when constructing new lift shafts, reinforcing
foundations or laying new sewage pipes, may
in some cases, especially in older city districts,
require an excavation permit in accordance with
provisions regarding conservation areas that
are included in KML, chapter 2 (1988:950). In
addition, shafts in the ground, for example for
the installation of radon wells, can also require
authorization.
Ventilation in historic buildings
Concrete casting under the threshold is not a solution that
the Swedish National Heritage Board recommends in ­a building with wooden beams. The measure was, however, considered necessary in this case and required an authorization.
Skridskopaviljongen, Kastellholmen.
Remains from the original facility for air heating shall be left
untouched. Damaged wooden beams in the double flooring are
replaced­and a new wood floor has been installed.
Skridskopaviljongen, Kastellholmen.
13 ( 60)
Ventilation principles
Stack ventilation system
Exhaust air
Intake air
Exhaust air system
Fan
Exhaust air
Exhaust air systems
With the help of exhaust air fans, the exhaust
air flow is regulated and ensured year-round. ­
In older buildings, existing brick flues can often
be used for exhaust air. Outdoor air is drawn in
via openings and leaks in windows and walls,
exactly as with stack ventilation.
Intake air
Supply and exhaust air system
Intake air
Ventilation unit
Supply air com­
ponents:
Damper, filter,
heat exchanger,
heat battery
and fan
enkel systemskiss.
Exhaust air com­
ponents:
filter, heat
exchanger, fan
and damper
Ventilation in historic buildings
Stack ventilation system
Stack ventilated buildings are constructed in
such a way that the ventilation is promoted by
the design of the building. In older buildings,
which were originally constructed with this system, the exhaust air ducts were made of brick
and served as both exhaust air flues and smoke
flues for fireplaces. Due to the stack effect – warm
air is lighter than cold air – the exhaust air rises
thermally up and out of the building. The greater
the difference in temperature between indoor
and outdoor air, the more effective the stack
­effect. Outdoor air (replacement air) is drawn in
through openings and leakage in windows and
walls. The building’s design, for example large
room volumes and rooms opening into one another in an enfilade, also contributes to good air
exchange. In summer, when the stack effect decreases, it is possible to create cross-ventilation
by opening windows.
Exhaust air
Supply and exhaust air systems
These systems have fans for intake air and exhaust air. Through that, the volume of supply and
exhaust air is regulated (balanced) and the risk
for draught is reduced. These systems require
advanced control equipment. Heat recovery can
be arranged with the help of a heat exchanger that
transfers the exhaust air’s heat to the supply air.
For conservation reasons, the possibilities might
be limited to running new ductwork. Existing brick
flues can often be used for exhaust air and sometimes even for supply air. Stairways and corridors
14 ( 60)
can sometimes be utilized as supply air ducts if
the building’s layout and openness allows. Transferred air to rooms with closed doors can be
arranged with a transfer air device or recessing in
thresholds.
Calorifères
The calorifère system is an older system intended
for both ventilation and heating, based on stack
ventilation. Outdoor air is drawn, through the
stack effect, into a heat chamber situated on
the lower level of the building. There, the air is
pre-heated during the winter. To regulate the air
flow and temperature to the different rooms on
the floors above, there are hatches at different
heights in the brick ducts through which air is
­allocated. The rooms have intake and exhaust
air vents at different heights. In the winter, the
air is fed to the ceiling and drawn out by the floor.
In this way the entire room is heated. In summer,
the top of the chimney is heated by the sun. The
flues therefore become warmer at the top than at
the bottom, which increases the stack effect. The
exhaust air rises out near the ceiling and the cool
outdoor air from the heat chamber is carried along
the floor. These systems are not automated and
therefore require a great deal of knowledge and
commitment from the property caretaker.
Hybrid ventilation
When you combine different ventilation principles
and create a unique combination, this is usually
called hybrid ventilation. It is common to combine
mechanical ventilation and natural ventilation and
utilize the best of both systems. In summer when
the stack effect is insufficient, fans are used for
ventilation. When the outdoor temperature falls,
the exhaust air fans can be shut down and stack
ventilation functions. This is conditional upon
the selected fans have very little resistance when
Ventilation in historic buildings
Calorifères
Exhaust air
Intake air
Heat chamber
Exhaust air
Hybrid ventilation
Fan
Ventilating via
automatic window opening
systems
Intake air
turned off. The system requires thorough adjustment. There are also developed systems with
automatic opening of windows, controlled by the
room climate and weather conditions. Here, the
outdoor temperature and wind conditions are utilized to create a good indoor climate.
15 ( 60)
Good advice
Design stage
Gamla Riksarkivet in Stockholm has an interesting ventilation
and heating system. Room air is heated through circulation
in heating columns. The air is taken in at the bottom and
released as heated air from the top. The building’s exhaust
air grilles are located near the floor. In this way, the cooler air
is drawn out and warm air close to the ceiling is drawn
downwards in the room.
Survey of the building’s design and existing ventilation system
A survey of the existing ventilation system must
be carried out; is it original? Does the building´s
design (layout, function, fabric etc.) constitute a
part of the system? Can the system be restored?
Will cleaning be sufficient? Can new technology
that does not require visible installations complement the system to improve performance? What
are the brief requirements? Is the present tenant
satisfied with the current ventilation? Can the
ventilation meet the proposed tenant’s breif requirements? Cooling requirements, increased air
flow? If needed, is there a possibility to run ducts
and install a ventilation plant? Perhaps the building already has a false ceiling and sufficient shaft
areas. A conservation officer must be consulted.
Studying the conservation plan to see what is permitted and doing a conservation assessment can
be of great help.
Locating of existing brick flues
If the building’s cultural value is so great that the
possibility of running ducts is restricted, this
­affects the system choice and also the achievable
indoor climate. If the system selection includes
existing brick flues, these must be found and
surveyed at an early stage, perhaps in occupied
office spaces. Old drawings can sometimes give
an indication of where the flues are. With the help
of these, the survey can be done on-site. Smoke
cartridges can be used to identify the flues in the
chimney. The survey can then normally continue
with the help of plumb lines. Radio detectors can
also be used to find the flues in the walls. It is important that flue survey is carried out at an early
stage in order to avoid surprises in the construction stage.
Original drawings showing chimney placement can be of help
in locating the flues. Here, we see a part of the floor plan for
Hårleman´s extension to Södra Banco from the 1700s.
Ventilation in historic buildings
16 ( 60)
CCTV-survey (filming) of brick flues from
the roof of the Skridskopaviljongen,
Kastellholmen, prior to a renovation of
the building and its ventilation system.
Measures in existing brick flues
To assess the status of the flues, possible air flow
as well as tightness to maintain fire compartmentation in the building, CCTV-survey (filming) and
gastightness test may be options. The flues must
often be sealed with mortar or ceramic compound.
There are different types of ceramic compounds
and some of these contain chamotte (grog) as
ballast with fibreglass reinforcement. Other compounds have pumice stone as ballast. Insertion
of a rigid or flexible flue liner can sometimes be
an alternative. Another technique is to insert a
soft flexible tube of composite material into the
flue from the top down. By inflating steam it gets
its final form following that of the flue and heat
treatment makes it irreversibly hardened. The advantage of this method is that damaged flues are
made tight and can be used as smoke flues at the
same time as the maximum flue dimensions are
maintained. The disadvantage is that you add new
materials into the building that are not authentic.
Sealing flues with mortar is totally in accordance
with conservation thinking. Insertion of a rigid or
flexible flue liner is a reversible solution. However,
you must remember that the flue dimensions will
reduce. When fitting old chimneys with axial fans,
it is important to renovate the entire length of the
flue, including above the fan. Otherwise, there is
a risk that decayed mortar will fall down and stop
the fan. Chimney tops must be equipped with a
net to hinder birds from nesting in them.
Choice of consultant
The consultant must have understanding for and
knowledge about the building’s character and
qualities. He must have a sensitivity and desire
to preserve older buildings. Provisions shall be
followed but not over-interpreted. In addition,
creativity is required in order to take into consideration the building’s design and characteristics
in the choice of system. References from similar
assignments must be shown.
Ventilation in historic buildings
Renovation of the brick flues was only done up to the height of
the new axial fans at Södra Banco. No renovation was done
from the flues upward and sometimes old mortar falls down
into the fans and causes stops in the operation.
Things to remember
during the design stage
•
•
•
•
•
Survey
Consultation with a conservation officer
Climate calculation
Tenant requirements
LCC-calculation
17 ( 60)
Relationship between the building´s design
and the operational requirements
Prospective tenants should be informed about
the special characteristics of the building and
its role in the Swedish cultural heritage. Indoor
climate calculations must often be carried out on
alternative systems and compared with the brief
requirement; sometimes a discussion must take
place with the tenant in order to modify the requirement. Information must be given as to what
will be required of the tenant so that the ventilation will function optimally. It may even be so that
the climate that can be achieved in the building
restricts the choice of operations.
Norra Banco’s windows do not have connected casements.
Therefore, the trickle ventilators are fitted to the inner casements. The outer casements have no draught strips.
Intake air via windows
If mechanical supply air is not an option, the
choice for the supply of outdoor air is often via
trickle ventilators in the window casement or
frame. A simpler solution that provides more
intake air and does not damage the window is
to avoid draught strips on the upper member of
the casement-frame. The tolerance that a window
must have between casement and frame in order
to be opened properly often provides sufficient air
flow. In selecting the method of supplying outdoor
air, consideration must be given to the outdoor
air’s level of purity and the risk of soiling.
Another principle is to utilize the space between
the inner and outer window casements for the intake of replacement air, which is then pre-heated.
This requires constant negative pressure, in other
words, mechanical exhaust air. In stack ventilated
buildings there is a risk that the air will go out
the wrong way between the panes and create
condensation.
Flow measurements that have been carried out show that
the natural gap between the upper casement and frame
provides more intake air than trickle ventilators. Draught
strips can be placed on other parts of the window to reduce
draughts. Skridskopaviljongen, Kastellholmen.
Ventilation in historic buildings
18 ( 60)
Making a survey of the presence of ground
radon and carrying out the necessary measures is
important. In buildings with mechanical exhaust
air or stack ventilation, negative pressure is created that can result in ground radon being drawn
in via air intakes and unsealed foundations.
To avoid intake air via windows being experienced as an unpleasant draught, it is important
to inform the tenant that the furniture should
not be placed too close to the windows. In older
buildings there were often enfilade of rooms with
passage areas close to the external walls and furnishing areas inside the rooms where iron stoves
and tiled stoves were located.
One cause of condensation between the casements can be
that the gap between the outer and inner casements has been
painted shut. Another cause can be that the room is not ventilated in the right way and instead, air is drawn out via the
closed windows.
Intake air via external walls
It is an advantage if you can pre-heat the intake air
upon entry. One way is to convey outside air via an
intake air radiator. The air is drawn in through the
external wall, filtered and pre-heated when passing out through the rear of the radiator to be dispersed over the radiator. Another way is to use an
intake air convector that consists of a heat battery
where outside air is pre-heated. It also contains ­
a filter. In order for service to be carried out, the
arrangement of furniture must be adapted to this.
Taking in outdoor air via grilles in the facade below the window ledges into the radiators is a technically good solution.
The air is pre-heated and also purified if you have filters in
the folding radiators. Whether the solution is possible to
carry out is mainly a conservation issue.
Vent convectors can provide pre-heated outdoor air when
needed.
Ventilation in historic buildings
19 ( 60)
Energy efficiency
The consulting group must ensure that the heat
load and energy needs are the lowest possible.
With exhaust air or stack ventilation it is often
difficult to arrange for heat recovery since the
possibilities to transfer the heat are limited. The
heat that can be recovered from exhaust air is not
sufficiently high-tempered to have any benefits in
the radiator system. Exhaust air heat pumps are a
possible solution but finding a location for them
can be difficult in older buildings. In addition, they
make conservation considerations more difficult
in regard to the necessary pipe and duct runs.
One way to limit the energy need is to control
operating times in consideration of working hours.
It is also possible to govern the air flow when
needed with the help of CO2-transmitters. With
low-flow alternatives (stack ventilation or exhaust
air systems) it must be remembered that the ventilating of emissions and odours from new furniture
and paint layers takes time. A separate ventilation
period without tenants may be necessary.
Indoor climate cooling
We impact buildings with higher heat emission
than before. The cause is lighting, computers and
other technical equipment as well as more staff
than the buildings were originally intended for.
Many of our historical buildings are actually old
residences intended for a small number of people.
The primary task is to work with reducing the
When installing plant rooms in attics in older buildings,
­special solutions are often necessary to reconcile the work
environment requirements with the building’s design.
Instead of installing climate cooling, it is possible to reduce
solar heat gains by using external sun-screens. Automatically
controlled awnings protect Södra Banco’s rooms from the
heat of the sun. In this way, the sun’s rays are obstructed both
before and after office hours.
Ventilation in historic buildings
20 ( 60)
heat load. If cooling is still needed in accordance
with the climate calculation, sun-shading should
be investigated as an alternative: automatically
controlled awnings can often be the solution.
From the 1800s onward, awnings were a common
resource to lower the indoor temperature in the
summer. Sometimes, for various reasons, it can
be difficult to get people to consider this alternative. Studies in old photo archives often show
that buildings have had awnings during an earlier
period. This is especially true of buildings in a city
environment. In addition, modern awnings are
more reliable than older models. Another way to
cool a building is to ventilate it at night via natural or mechanical ventilation. If the fabric of the
building has sufficient thermal capacity, cooling
prior to the forthcoming warm working day can be
very effective. When fitting out a previously unfitted attic, it should be remembered that in such
an environment air-conditioning is almost always
required, which results in a larger plant space
requirement and increased installation and operating costs.
Re-utilisation
It can be difficult to find details, ventilation grilles,
etc., that fit into the historical environment. Such
The contractor must understand the principles for ventilation
facilities. If you are going to achieve stack ventilation in a
duct, it must be installed at a rising angle. The photo shows a
new duct that was installed horizontally, which was noted by
the inspector.
things are no longer manufactured. The far-sighted
manager can save details from demolitions and
renovations for later use. When complicated ventilation systems are installed in older buildings,
there is usually a surplus of needless details,
which often are thrown away. You have to keep
your eyes open.
Procurement and construction stage
Choice of contractor
The choice of contractor is especially important
for installations in listed buildings. For measures
involving brick flues, survey, sealing, etc., a contractor who understands this type of work must
Things to remember
during the procurement and construction stage
•
•
•
•
Choice of contractor
Inspector
As-built drawings
Documentation entered into the conservation plan
Old ventilation grilles from demolitions should be saved for
re-use.
Ventilation in historic buildings
21 ( 60)
contractors involved. Ventilation facilities must
be documented in the conservation plan.
Management stage
User instructions
User instructions shall be formulated prior to the
tenant moving in; the project manager can easily
understand how ceiling fans and intake air radiators shall function and work together, but there
are examples of staff sitting all summer sweating
without understanding that it is allowed to open
the windows. User instructions shall be posted
in a suitable location and an inventory should be
taken each year to ensure that all affected personnel have knowledge of how the ventilation system
works.
In the conference rooms in older buildings there is not always enough ventilation for long sittings. Breaks and the
opening of doors and windows may be needed. Södra Banco.
be engaged. Ventilation contractors can often
only run ducts and put together fan systems.
Chimney sweeps and bricklayers often have to
be hired. For unconventional ventilation systems
this involves choosing a contractor who is used to
finding unconventional solutions so that the entire
concept of the system is not lost. One piece of advice is to engage the ventilation consultant as inspector since that is the person who understands
the system best.
Documentation of the contract
Documentation of the completed contract must be
carried out. Certificates of selected materials and
the film of the flue inspection etc. must be saved.
Since the location of the flues in reality seldom
is in accordance with drawings, making as-built
drawings after measurement are especially important. This is often forgotten since there are many
Ventilation in historic buildings
Follow-up
When a renovation of a property has been carried
out and the tenant has experienced the indoor climate during a year (summer and winter weather),
it is valuable to monitor the indoor climate. Does
the ventilation system function as it should? Are
the personnel satisfied? A performance inspection and a user survey will provide the answers.
There is probably no subject that can be perceived
so differently by people as ventilation. In certain
cases the solution can be simple: the climate in a
room may be perfect for one person but not for another. Such problems can sometimes be solved by
having people change rooms with each other.
Things to remember
during the management stage
• User instructions
• Review of system user knowledge
• Performance inspection
22 ( 60)
Eight examples in Sweden:
Eight buildings in SFV’s property holdings have
been selected here since they illustrate the different ways to improve ventilation in buildings that
are historically valuable. The ventilation solutions
represent different principles for air distribution.
The solutions have been possible to implement
while complying with conservation requirements.
The buildings’ design, which is a part of the
original ventilation system, has been utilized and
consequently the buildings’ authenticity has been
preserved.
early 2000s and was fitted with exhaust air fans
and an automatic window opening system.
1. Amiralitetshuset page 24–28
Amiralitetshuset is located on Skeppsholmen in
Stockholm. The building was constructed in the
1600s and has undergone several renovations
over the centuries. During the latest renovation at
the end of the 1990s, the building was fitted with
a new exhaust air system.
6. Landshövdingens stall page 46–48
Today, the fairyland museum, Pelle Svanslös
Hus, is housed in a building in Uppsala, which
was originally constructed in the early 1800s as
a guest stable for the county governor’s visitors.
The building underwent a renovation prior to
being turned into a museum and was fitted with
exhaust air fans that are in operation during the
summer. Other seasons of the year, the building is
stack ventilated.
2. Sjöreservens kasern
page 29–31
This building, from the early 1900s, is located
on Skeppsholmen in Stockholm. It was used by
the naval reserve, which was responsible for the
mooring of military ships and the island’s fire department operation. The building was renovated
in the late 1990s and was fitted with a new supply
and exhaust air system for the conference rooms.
The other rooms were fitted with an exhaust air
system.
3. Dekanhuset page 32–35
Dekanhuset in Uppsala traces its roots back to
medieval times. The building has been remodelled
and renovated on several occasions. In the latest renovation in the early 2000s, a new supply
and exhaust air system with heat recovery was
installed.
4. Gamla gymnasiet page 36–41
Gamla Gymnasiet in Karlstad is one of only a few
high schools that existed in Sweden in the mid1700s. The building underwent a renovation in the
Ventilation in historic buildings
5. Ladugården page 42–45
From the middle ages and forward, the island
Arnö in Lake Mälaren, has been a strategic location for the church and Sweden’s sovereigns. The
barn (Ladugården) is from the 1800s and was
renovated in the late 1990s. The building is stack
ventilated and fitted with exhaust air fans, utilized
during summer.
7. Södra Banco page 49–53
Södra Bancohuset in Stockholm is Europe’s oldest
bank building. Since the mid-1600s, office operations have been carried out here. In connection
with the building’s foundation needing reinforcement, an interior renovation was carried out and
the building’s ventilation system was renovated.
The building’s original ventilation system and its
design have been taken into consideration and
complemented with new technology that does
not affect the building’s authenticity. The result is
a supply and exhaust air system combined with
stack ventilation.
8. Thielska galleriet page 54–57
On the eastern part of Djurgården in Stockholm,
the financier Ernest Thiel erected a palace. It became an impressive building with a, at that time,
modern ventilation system. The Calorifère system
not only ventilated the building’s exhibition halls,
but also contributed to heating during the winter.
23 ( 60)
1. Amiralitetshuset
Skeppsholmen, Stockholm
History
Construction of Amiralitetshuset, which is located
on Skeppsholmen in Stockholm, began in 1647
and the building was first used in 1650. The architect was most likely the Dutchman, Louis Gillis.
Originally, the building housed the admiralty’s
offices and meeting rooms, as well as a sail store
on the top floor. Amiralitetshuset has undergone
several renovations but the sandstone portal is
original. In 1680, the Royal Swedish Navy relocated
to Karlskrona and from the late 1600s, Amiralitets­
huset was used as an archives. The archives
were relocated in the 1750s and the building was
converted into a granary and the exterior drastically altered. From 1794, parts of the building were
used as a barracks. Between 1844 and 1846, a
major renovation and restoration were carried
out by architect Fredrik Blom. The building was
converted into a barracks and acquired its current external design, which reflects the building’s
original appearance. However, the corner towers
are new additions. In 1952, the building was refurbished by architect Rudolf Cronstedt to serve as
the offices for the East Coast Naval District Staff,
Owner
• The Royal Swedish Navy
• Swedish Fortifications Agency
• National Property Board Sweden
Tenants
•
•
•
•
The Royal Swedish Navy and state have used
the building for many different activities over the years such as:
Barracks
Offices
Sail store
Granary
• Accommodation for sick soldiers
Amiralitetshuset on Skeppsholmen has undergone several
renovations. The latest was carried out at the end of the 1990s.
Ventilation in historic buildings
24 ( 60)
becoming once again Amiralitetshuset. It has
been listed as a historic building since 1935.
Renovation
Over the years, the building has had many different tenants and was in need of external renovation. The building also needed internal renovation
in order to be leased for modern office operations.
The renovation was carried out from 1996–98 and
included the restoration of the facades to their
1850s appearance. Internally, a lift, an emergency
stairway and modern services were installed. A
new underground ventilation and heating plant
room was built to the building’s western side on
the slope facing the water.
Amiralitetshuset is located on the western side of Skeppsholmen, in the center of Stockholm.
Ventilation before the renovation
The building had stack ventilation with intake air
via windows and vents in the external walls and
exhaust air via brick flues in chimneys. During the
1950s, the building’s bathrooms had been fitted
with mechanical exhaust air. The ventilation system did not work since the old brick flues were not
tight and also partially clogged.
Conditions for renovation of the
ventilation system
The building has thick external walls made of
stone and brick. The room volumes are spacious.
Therefore the air exchange can be low compared
with modern buildings, which often have lower
ceiling heights and therefore, smaller room volumes. Installing air conditioning systems are not
necessary in these kinds of buildings. By cooling
the fabric of the building by night ventilation, the
mean radiant temperature of the space is reduced,
improving the thermal comfort the following day.
Providing all floors with a traditional, mechanical
supply and exhaust air system was not possible
due to the building’s protection orders. I­nstead
the existing brick flues were renovated and connected to an exhaust air fan.
Ventilation in historic buildings
The building with its enfilade of rooms have generous room
volumes. The tiled stoves that remain in the building have
been plugged. The flues are used for exhaust air.
State-owned listed building
The building has been listed as a state-owned
historic building since 1935 and is subject to
protection orders, which state that alterations
to the building’s structure may not be carried out without the authorization of the Swedish
National Heritage Board.
25 ( 60)
Conservation principles
In the renovation, the ambition was to restore the
building’s room volumes and room relationships.
Many modern, lighter internal walls, which were
added to the building in the 1950s, were demolished and previously closed door openings in
load-bearing walls were opened up. This recreated
the enfilade of rooms and provides important air
movements. The parts of the buildning that are
most worthy of preservation are the external brick
walls, the portal, stairway and the joisted floors.
Despite the fact that the facade may not be altered, the Swedish National Heritage Board gave
an exemption for drilling below the window ledges
for intake air. The building’s old flues could be
renovated and used for mechanical exhaust air.
Authorization was granted to fit out the unfitted
attic level for new meeting rooms.
The Swedish National Heritage Board gave authorization to
drill air holes through the facade and install intake air grilles
so outdoor air can flow in behind the rooms’ radiators.
Ventilation after renovation
During the renovation, mechanical exhaust air
ventilation was installed, serving all floors. In
addition, mechanical supply and exhaust air ventilation was installed in the attic, with provision
for a supplementary increase in the ventilation
flow rate.
Intake air
Behind every window radiator there are two
holes with a diameter of 7 cm drilled diagonally
through the external wall. On the facade, below
the window ledges, discreet ventilation grilles
are mounted. In that way, the outdoor air is preheated. The radiators are fitted with filters. To
change these it is easy to fold out the radiators
from the wall. The supply air unit for the attic level
with meeting rooms is located in the heating plant
room, which is located outside the building. The
former boiler chimney is used as a supply air duct
serving attic level.
When a radiator is folded away from the wall for a filter change,
it is possible to see the intake air holes in the external wall.
Ventilation in historic buildings
26 ( 60)
Exhaust air
The existing flues have been cleaned and tightened with plaster. Control valves have been
mounted in the brick flues in each room. All brick
flues are connected at the ridges in the attic with
sheet metal ductwork that directs air down to the
exhaust air fan, which is located in the attic. The
exhaust air exits via the existing chimney.
Experiences
A survey of the flues must be done at an early
stage, preferably in the design stage. For this
project, no survey was done; the work with the
existing brick flues was started much too late;
the offices were already renovated and painted.
The old drawings that the project planning was
based on were incorrect, which meant that new
Outdoor air is drawn in via holes in the facade behind the
­radiator, which pre-heates the air. The small photo shows the
intake air grilles in the radiator in the closed ­position.
The exhaust air fan is located in the attic. The flues in the existing The supply air devices in the meeting rooms in the attic get
chimneys are connected in the ridged attic with horizontal sheet
their air via a flue that was previously a boiler chimney.
metal ducts that lead down to the exhaust air fan.
Ventilation in historic buildings
27 ( 60)
holes had to be drilled for vents. Consequently,
the rooms had to be repainted. After the tenant had moved in there were complaints about
draughts from the windows. The workplaces were
positioned close to intake air radiators and this,
in combination with the fact that the radiator
temperature, for energy-saving reasons, had been
lowered, made the incoming air feel cold. The tenant would then close the intake air vents in the radiators, which in turn caused the ventilation to be
inadequate. In addition, the number of workplaces
in every room had increased relative to what was
planned for. With the right information to the
tenant and operating staff, these problems have
been rectified. Informing the tenant about how the
ventilation functions is essential.
Outline diagram, flows in Amiralitetshuset
The exhaust air fan on the top floor draws out the air
through existing brick ducts
Outdoor air is drawn
in through grilles in
the facade, is filtered
and pre-heated in the
radiator
The supply air unit,
which only serves the
conference rooms in the
attic, contains damper,
filter, heat battery
and fan
Ventilation in historic buildings
28 ( 60)
2. Sjöreservens kasern
Skeppsholmen, Stockholm
History
This building was constructed in 1907 on the
southeast side of the island Skeppsholmen as a
barracks for the naval reserve, which was responsible for the mooring and dry-docking of military
ships and for dealing with any fires that occurred
on the docks.
Renovation
The barracks were renovated in 1997 for the
National Property Board Sweden, which since that
time has had one of its management offices there.
The building, which is made of timber, had poorly
insulated external walls. The suspended floor
had rotted. This was rectified in the renovation.
The external walls were further insulated and the
joisted floors were renovated. A lift and a new
cellar area containing a new heating plant and
storage area were installed. The attic was fitted
out as a staff room and conference room.
Ventilation before the renovation
The building was stack ventilated and had never
had acceptable heating. Outdoor air was drawn
into the building via slotted vents, from the mid1930s, located below the window seats. The ventilation did not function well.
Owner
• The Royal Swedish Navy
• Swedish Fortifications Agancy
• National Property Board Sweden
Tenants
The building has been used as a barracks, art
studio and currently serves as an office for the
National Property Board Sweden.
Sjöreservens kasern on Skeppsholmen, currently a local
­office for the National Property Board Sweden.
Ventilation in historic buildings
29 ( 60)
Conditions for renovation of the
ventilation system
The building’s rooms had large volumes and the
ventilation was designed accordingly. When a
new operation was coming in, this required a new
room layout in order to have many office spaces.
This required enhanced air exchange. The high
ceilings allowed false ceilings in the corridors.
In connection with the additional insulation
of the facade, it was easy to mount air intakes
below the window ledges.
Conservation principles
The entire island is a state-owned listed conservation area. The exterior of Sjöreservens kasern
is subject to protection orders. This meant that
Air intake below the window ledge.
there was no problem in renovating the building
to a modern standard and installing a new ventilation system.
Ventilation after renovation
The building was fitted with mechanical exhaust
air and air intake using intake air radiators. Since
the building has a light timber frame, cooling was
necessary. The meeting rooms, therefore, have
mechanical supply air with cooling. The ­offices
have been fitted with cooling baffles and ceiling
fans that are controlled manually ­according to
needs. In the summer, the ceiling fans, so-called
Casablanca fans, help to disperse the cool air in
the rooms. In the winter they force the warm air
down, which would otherwise stay near the ceiling.
Intake air
Under every window there is an intake-air radiator;
behind this the air is drawn in through slits in the
facade. On the outside, the slits are covered by
grilles placed just below the window ledges. The
radiators are fitted with filters. To change these
you can simply fold out the radiator from the wall.
The large meeting room on the ground floor and
the meeting room in the attic are provided with
supply air via a unit placed in the attic. The supply air unit has a rotating heat exchanger for heat
recovery from the exhaust air. The air intake is located on the northern gable in order to obtain the
coolest air possible.
State-owned listed historical building
The entire island Skeppsholmen is a state-
owned listed conservation area in accordance with the Ordinance regarding state-owned listed buildings since 1935 with a change in conserva-
tion status in 1993 and 1998. The exterior of the building is subject to protection orders.
External air is drawn into the radiator, which is foldable and
has a filter.
Ventilation in historic buildings
30 ( 60)
Exhaust air
The building has been fitted with mechanical exhaust air via ducts connected to a unit located in
the attic. Heat in the exhaust air is recovered and
added to the intake air via the heat exchanger. The
air emission vent is located on the southern gable.
Experiences
The radiator temperature must be sufficiently
high in order to be able to heat the intake air. User
instructions are important for instructing people
how to operate ceiling fans, cooling baffles, increased air flow and intake air radiators. Tenants
should also be made aware that placing furniture
near windows is not recommended. This is because some people might experience draughts
and also because the property caretaker must be
able to easily change the filters in the radiators.
Here, you can see the exhaust air grille on the southern gable.
The air intake is located on the northern gable for cooler air.
Outline diagram, flows in Sjöreservens kasern
Air handling unit containing supply and
­e xhaust air fans,
filter, heat exchanger,
heating and cooling batteries
Ceiling fans help to even
out room temperatures
Outdoor air is drawn in
via grilles in the facade,
filtered and pre-heated in
each radiator
The offices have been fitted with ceiling fans. The fan has different speed settings and reversible rotation settings. In the
winter the fans help to push down the warm pillow of air near
the ceiling. All workrooms and conference rooms have cooling
baffles. In the summer, the ceiling fans circulate the cooled
air in the rooms.
Ventilation in historic buildings
31 ( 60)
3. Dekanhuset
Uppsala
History
The building, called Dekanhuset, was given by
the Bishop of Skara during his term of office as
dean in Uppsala in the beginning of the 1300s to
the Uppsala Free Deanery, now called diocese.
The building is believed to have been destroyed
in 1447 by fire, but a new building was erected
on the old foundation five years later by the
­arch­bishop at that time. In the mid-1700s the ­
property was purchased by university treasurer,
P. Julinskiöld. He rebuilt it to be the largest palatial
residence in Uppsala. At the end of the 1700s, the
property was transferred to Uppsala University
where it was used as both an apartment building
and school. Today, elements from all epochs can
be seen in Dekanhuset. A part of the cellar, from
medieval times with its brick cross-vaults, is intact. Certain rooms still have interior decorations
from the Julinskiöld Palace. The design of the
facade and windows is from the early 1800s when
the building was converted into a school. The
formal hall with a double storey ceiling height is
also from this time. The building is a state-owned
listed building.
Renovation
When SFV´s tenant, the Faculty of Theology,
moved out, a renovation was necessary. During an
earlier renovation of the building, the old formal
hall with a double storey ceiling height had been
rebuilt as two stories. For this renovation it was
decided to restore the double storey ceiling height
of the formal hall.
Owner
•
•
•
•
•
•
Dean and Bishop of Skara, 1300s
Uppsala Free Deanery, 1326
University treasurer, P. Juhlinskiöld, 1746–
1768
Uppsala University, 1768–1830
Swedish Church
National Property Board Sweden
Tenants
The building was initially used by the church but was converted in the 1700s to a private palace. After that, the building was used as an apartment building and then renovated to house various schools. Today, the building is used for offices.
Dekanhuset, Uppsala. Presently the district office for SFV,
division NO.
Ventilation in historic buildings
32 ( 60)
Ventilation before the renovation
The ventilation was adapted to the church´s education premises, the Faculty of Theology. They
had a mechanical supply and exhaust air unit that
served the large teaching rooms. The small rooms
had a poorly functioning stack ventilation.
Conditions for renovation of the
ventilation system
SFV wanted to design the new ventilation system
so that every floor could be able to be separated
for different tenants if needed. When the formal
hall was restored into its original double storey
ceiling height, this resulted, however, in floors
3 and 4 becoming one fire compartment. It was
also important that the new ventilation system
should be modern and adapted to the building for
preserving its unique character. Holes that were
already made in the walls for the old mechanical
ventilation system could be reused when installing the new system.
During this renovation of the old formal hall the original
double storey ceiling height was restored.
Conservation principles
The building´s medieval cellar, exterior, frame,
room layout and purpose-built interior decorations
are protected by the protection orders and must
be left untouched to the greatest extent p
­ ossible.
Unavoidable holes have therefore, to the extent
possible, been located to existing or previously
filled holes. All installations have been carried out in such a way that they are reversible
and easy to maintain and replace. A large new
State-owned listed building
The building has been listed as a state-owned
historic building since 1935 and is since 1993 subject to protection orders, which state that alterations to the building’s structure may not
be carried out without the authorization of the Swedish National Heritage Board.
Openable windows are still an appreciated complement to the
mechanical ventilation in summer.
Ventilation in historic buildings
33 ( 60)
opening was required in the joisted floors for
the installation of a lift. At that time, a services
shaft was constructed adjacent to the lift beside
the stairway in the newest part of the building.
Consequently, all the room volumes remained
unaltered. Supply air is distributed through purpose-built wood gratings, designed to fit in with the carpentry of the building.
Ventilation after the renovation
A mechanical supply and exhaust air system with
heat recovery, which was adapted as much as
possible to the building, was chosen. Water batteries in the exhaust air unit in the attic recover
the heat in the exhaust air. The heated water is
distributed via the services shaft to the supply
air unit in the cellar. The supply air can also be
cooled when needed by the use of groundwater.
During summer the fabric of the building is cooled
by night ventilation, i.e. night cooling. Fan coolers
are located in several areas in the building and
are placed in purpose-built benches or covers
designed to look like tiled stoves.
Supply air
The space under the building consists of three
parts. There is the original cellar from medieval
times with cross-vaults that cannot be altered.
Then there is an 18th century cellar that has
been used as a heating plant room for some time.
Between these there is an unexcavated area.
A new supply air unit has been located in the 18th
century cellar. The outside air comes from a newly
built air inlet outside the building at ground level.
The unit can distribute pre-heated or cooled air.
Cold water is pumped in via a borehole and after
the cooling is utilized, the heated water is pumped
back into the ground via two other boreholes. The
supply air ductwork is run through the unexcavated part of the ground floor beneath the joists to a
vertical services shaft located alongside the new
toilet groups and storage areas.
The conference rooms and certain offices and corridors are
­fitted with purpose-built benches with fan coils. They ­provide
either chilled or heated air, as required by the room temperature controls.
Ventilation in historic buildings
34 ( 60)
Exhaust air
The building had very good conditions for hidden
exhaust air. All rooms had separate clay brick
flues. They were cleaned and sealed. In the un­
fitted attic, these flues could be connected by
ducts to an exhaust air unit. The air is let out via
previously built chimney-like exhaust air hoods on
the roof. The exhaust air unit has a water battery
for heat recovery that is connected to the supply
air unit in the cellar for pre-heating the supply air
when needed.
Experiences
Through the renovation, SFV´s wish to get a
ventilation system that could function for many
different tenants was fulfilled. Utilizing the un­
excavated area underneath the double flooring
for running ductwork has been very successful.
The entire building has a very effective and
­aesthetically appealing ventilation solution that
offers the property owners the maximum flexibility when leasing of premises. The current tenant
is very satisfied with the system.
This new fan air-cooler has been designed to look like a tiled
stove to fit in with the environment.
Outline diagram, flows in Dekanhuset
Exhaust air fan in the attic with heat recovery battery
Exhaust air via existing
brick flues
Air intake via a hood
located on the ground at
the rear of the building
Supply air via a centrally located shaft
Supply air unit with cooling
and heating of air
Air inlet through a new hood at the rear of the building.
Locating air inlets high up is best, but was not possible
due to aesthetic reasons.
Ventilation in historic buildings
35 ( 60)
4. Gamla gymnasiet
Karlstad
History
In the middle of the 1700s there were only a few
high schools in Sweden. In the Karlstad diocese
there was an elementary school with education
for high school proficiency. The school was made
of timber and when it burned down in 1752 the
church decided to construct a new high school
with an observatory on the roof. The assignment
was given to architect Carl Hårleman. He died in
1753 but left behind his signed drawings. When
the construction of the building started, his colleague and successor, architect and director Carl
Johan Cronstedt had revised and adapted the
drawings. In 1754, construction of the high school
was started. The building was completed in 1759.
Architect Johan Eberhard Carlberg was responsible for the construction together with senior
master, Johan Fryxell. Carlberg is named as the
architect that designed Karlstad High School.
The special stepped gables are attributed to him.
The building has been a state-owned listed building since 1935.
Renovation
The building has been renovated and altered on
several occasions due to wear and tear, neglected
maintenance and poor masonry. All major changes
to the building were carried out before it was
listed as a state-owned historic building. The most
recent renovation was carried out in 2005–2006.
Owner The Swedish Church owned the property
until 1929 when it became the property of
the state. Since 1993 it has been owned by the National Property Board Sweden. Tenants Over the years the building has housed
various operations and has been used as a
high school, field hospital, pharmacy, for storing cultural and historical museum collections, and administration for cathedral chapters and the County Administrative Board. Currently, the premises are used for offices and museum and association operations. Gamla gymnasiet in Karlstad, with the observatory on the roof.
Ventilation in historic buildings
36 ( 60)
Ventilation before the renovation
The building was stack ventilated. The exhaust
air rose out via tiled stoves with the help of temperature differences, the stack effect. Replacement air, (outdoor air), was drawn in through
leakage between window frames and window
casements. However, the ventilation did not
function. The brick flues had not been cleaned
and had cracks due to settlement damage. Some
parts of the flues had disintegrated.
Conditions for renovation of the
ventilation system
The building was constructed using the building techniques of the period, with thick stone
and brick external walls and with large ceiling
heights, which provide good conditions for stack
ventilation during the part of the year when the
outdoor air is cooler than the indoor air. During
the summer months the stack effect decreases
and with that, the exhaust air. The intention was
to create a ventilation system that could function
year-round. The attic and cellar have always been
storage areas and would remain so, and therefore did not require extra ventilation and cooling,
which would otherwise be necessary in order to
have workplaces there.
Outdoor air is drawn in via the gaps between the upper part
of the window-casement and the window-frame, where there
are no draught strips. The rest of the window has strips to
prevent draught.
State-owned listed building
The building has been listed as a state-owned
historic building since 1935 and is subject to protection orders, which state that alterations to the building’s structure may not be carried out without the authorization of the Swedish National Heritage Board. Prästsalen (Priest´s hall) with an automatic window opening
system.
Ventilation in historic buildings
37 ( 60)
Conservation principles
As a listed building, it is required that all walls
remain intact. This means that new installations
can not be hidden in the walls. The technical additions must then be designed so that the rooms
retain their architectural character. SFV´s cultural
heritage unit proposed, at a very early stage in
the design process, that the building´s original exhaust air flues should be restored. This, together
with the engaged ventilation consultant proposing
an automatic window opening system, made the
conservation principles quite simple. The only
internal ventilation additions were the motors controlling the automatic opening of certain window
Since it was too costly to rebuild all the disintegrated brick flues casements and the visible electrical and computer
some of them were repaired and fitted with flexible flue liners. connections to these. The location of the motors,
was an aesthetic conservation issue. The fact that
this automatic window opening system actually
was able to be used was due to the window casements having been replaced in the 1920s with
coupled window casements, which were suitable
for this solution. If the casements had been original from the 1700s things would have been different. 18th century casements can be very fragile
and are not suited for this motorized window
opening system.
Since the old chimney stacks are not used anymore for fire,
exhaust air grilles have been mounted directly in the flues
above the tiled stoves.
Ventilation in historic buildings
Ventilation after the renovation
The natural ventilation system has been retained and developed. Air still comes in via gaps
in the windows but certain rooms on the second
floor have an automatic window opening system.
Exhaust air still rises thermally through the old
brick flues. Propeller fans were installed in the
flues and are turned on when the stack effect
ceases during the warm part of the year. In this
way the building has a functioning ­exhaust air
system year-round.
38 ( 60)
Intake air
Replacement air is drawn in via gaps between
the upper part of the window-casement and the
window-frame, where there are no draught strips.
Exhaust air
All exhaust air flues were made of brick (in chimney stacks) and in a very poor condition before the
renovation. During the survey it was discovered
that the flues had very restricted cross sectional
areas. This meant that they could not provide the
required air exchange for a good indoor climate.
Since the brick flues were to be used for exhaust
air they had to be renovated. It was possible to
seal some flues with plaster. Other brick flues had
partially disintegrated and were too costly to rebuild. Therefore flexible flue liners were inserted,
even though this results in a reduced cross sectional area. Initially, many exhaust air flues served
more than just one room; sometimes rooms on
other floors. This problem was unable to be solved
and instead, attempts were made to minimize
the number of shared flues and also ensure that
no rooms on different floors were served by the
same flue. Fire compartmentalizing in accordance
with today´s requirements could not be achieved
and the entire building is one fire compartment.
Axial fans (propeller fans) are installed on top of
the chimneys. The fans ensure that the building
has a background ventilation during the warmer
part of the year (March through September), when
the stack effect ceases. The fans are turned off in
winter. They provide virtually no resistance when
turned off and therefore, do not counteract the
stack effect. The original exhaust air grilles have
been kept to the extent possible but new ones
were manufactured. Behind these grilles control
valves are mounted. They are adjusted to provide
the correct exhaust air flow since one fan serves
all the flues in each chimney. Since the exhaust
air flues only provide background ventilation, the
exhaust air in certain rooms must be increased by
cross-ventilation via an automatic window opening system.
Ventilation in historic buildings
Control valves which are adjusted to provide the ­correct exhaust air flow are located behind the exhaust air grilles.
The wet areas have separate exhaust air fans.
39 ( 60)
A motor for opening the window automatically is placed on
the window’s transom. The electrical cord is visible along the
window frame.
Intake and exhaust air via automatic
window opening systems
In some parts of the building the possible rate of
exhaust air via flues can not provide the acquired
air exchange for the operation being carried out
there. To compensate for this an automatic window opening system has been installed. For every
set of windows, one of the upper casements is
equipped with a motor-controlled arm that can
automatically open the window casement as much
as is needed. The opening of the windows – how
much and how long – is governed by carbon dioxide meters that are placed in various zones in the
building and also by the weather station on the
roof. It has a meter for wind direction, wind veloci­
Installations in Prästsalen
New motors for
opening the windows automatically; 1 motor per
window
Existing
radiators
Outline diagram of the automatic window opening system. The system works well in rooms with windows facing in several directions.
Ventilation in historic buildings
40 ( 60)
ty, rain and indoor and outdoor temperature.
During the summer, cross-ventilation is done at
night by the automatic window opening system
for cooling the fabric of the building prior to the
forthcoming, warm working days.
Experiences
The National Property Board Sweden had an interest in testing an automatic window opening
system and the decision to do so has been very
successful. The property´s tenants are satisfied with the ventilation. The air is perceived as
pleasant. The tenants have no problem adapting
to the building´s conditions. In those rooms with
automatic window opening, everyone knows
to use paperweights for their papers due to
the cross-ventilation. During the warm summer
weeks, extra ventilation at night cools the building. This, in combination with the building´s very
thick external walls, has helped to maintain a
satisfactory indoor temperature even during extremely hot summers. The thick brick walls assist
night-time cooling, which evens out the daytime
temperature. The purpose of the renovation of the
building was to retain the original ventilation system and complement it with new technology – an
automatic window opening system – which is not
at variance with the conservation of the building.
Consequently, for aesthetic reasons, external
air is drawn in through natural gaps. No draught
strips are used between the upper part of the
window-casement and the window-frame.
The weather station on the roof controls the automatic
window opening system with a meter for wind direction,
wind velocity, rainfall and temperature.
Outline diagram, flows in Gamla gymnasiet in Karlstad
Exhaust air fans in operation
during the summer
Exhaust air via clay
brick flues, through
stack ventilation
Complements with automatic window opening
system on the second floor
Air intake via gaps between
the frame and casement
on the upper edge of the
window
Ventilation in historic buildings
41 ( 60)
5. Ladugården
Biskops-Arnö
History
Biskops-Arnö is a small island in Lake Mälaren. ­
It is located close to the mainland in the munici­
pality of Håbo outside Enköping. The island
has a long history as a cultural landscape with
interesting buildings. In the 1280s the island
was purchased by Uppsala Cathedral as a link in
the church’s desire to have branches along the
important waterways from Uppsala to the Baltic
Sea. In 1325, work began with the construction of
the castle, Arnöborg. Agricultural activities and
livestock activities were carried out here and Uppsala’s bishops were allowed to use the island as
a residence and private summer place. Of the impressive castles, today there remains only a part
of the cellar with its medieval brick vaults. New
buildings for residences and farming have been
constructed over time. In the 1700s a new main
building with two wings was constructed, still preserved today. The agricultural landscape with its
flora and bird life is unique for Sweden.
Renovation
When the folk high school needed to expand with
more classrooms in the middle of the 1990s, Ladu­
gården (the barn) from the 1800s (at that time vacant) was utilized. Here, it was possible to have an
effective lecture hall and computer rooms. There
was also space for a photo lab and offices.
Ventilation before the renovation
Before the renovation, the barn had no special
ventilation system. The building was ventilated
through openings and leaks in walls and ceilings
and by cross-ventilation.
Conditions for renovation of the
ventilation system
What was desired was a ventilation system that
was as simple as possible, cheap to install, not
visible and easy to manage by the tenant.
Conservation principles
The entire island is a state-owned listed conservation area so it is important to preserve all
Owners
•
•
•
•
•
•
1200s: Birger jarl’s son
1500s: Gustav Vasa
1600s: Swedish nobles
1700s: Swedish Crown
1800s: Swedish State
Today: National Property Board Sweden
Tenants
The island has had many different tenants:
Uppsala’s bishops, Swedish Kings, including Gustav Vasa and his family, noble families
and captains for the Royal Lifeguard Mounted Regiment. Since 1956, the foundation, Nordens Biskops-Arnö, has operated a folk high school
on the island.
The barn has been renovated to house classrooms. The building has exterior protection orders and authorization was granted
to complement the roof with ventilation hoods.
Ventilation in historic buildings
42 ( 60)
Intake air grilles in the facade. The former manure hatch has
been cut in the lower edge. The gap is sufficiently large to
provide air into the building even with the hatch closed.
An existing hatch that has been slightly opened is used as an
air intake to the heat chamber (calorifère).
buildings. The exterior of the building is subject
to protection orders. This meant that during the
renovation, external walls and the roof, to the
extent possible, should not be altered. Existing
hatches and doors have been utilized for outdoor
air intakes without this being seen as an alteration. In the facade, the brick drainage pipes,
which previously let air into the building, still
remain. These have been internally sealed since
they are no longer needed for air exchange. The
building has an original reed roof, which was covered with sheet metal in the mid-1900s. Since the
reed roof was to be retained, the roof could not be
insulated. Instead, roof insulation was laid in the
joisted floor of the attic. Authorization was granted
to complement the building with four exhaust air
hoods in traditional barn style.
State-owned listed building
The building has been listed as a state-owned
historic building since 1935 and is since 1993
subject to protection orders, which state that
alterations to the building’s exterior may not be carried out without the authorization of the
Swedish National Heritage Board.
Ventilation in historic buildings
The air into the classrooms comes via vent convectors.
The outdoor air can thus be pre-heated when needed.
43 ( 60)
Ventilation after renovation
The building is stack ventilated and complemented
with exhaust air fans, utilized during summer.
To get sufficient air exchange in the large assembly room, it
is ventilated with a so-called calorifère system. In the photo
you can see the intake air grates in the wall facing the heat
chamber.
The large lecture hall is exhaust air ventilated by the newly
constructed air shaft above the wood gratings in the ceiling.
Ventilation in historic buildings
Intake air
Outdoor air is drawn in via vent convectors,
equipped with batteries for pre-heating. In general, cross-ventilation via opening windows, can
easily be done in the summer. The large lecture
hall also has ventilation and heating during the
winter via a heat chamber, so-called calorifère.
Exhaust air
The air rises upward and out via three newly
constructed air shafts with the help of the stack
effect in the winter and fans in the summer. Each
air shaft has an axial fan. The fans are controlled
by timers that the tenant sets. There is a hatch at
the bottom of every shaft, which by the use of a
rope, can be set in different positions so that the
desired air flow can be obtained. The bathrooms
have their own mechanical exhaust air, which is
on constantly. The photo lab also has a separate
exhaust air fan that is automatically activated
when the room is in use.
The photo lab has a separate exhaust air fan, which is put
into operation when needed.
44 ( 60)
Experiences
The ventilation system meets all the function
­requirements that have been made. Course arrangers and course participants are very satisfied with
the ventilation.
The air shaft viewed from underneath where the axial fan can
be seen. With a rope, the hatch can be regulated to obtain the
desired exhaust air flow, either via stack ventilation or fan.
In the inner part of this classroom there is an air shaft in the
ceiling with an axial fan. The fan is started by the tenant when
needed.
Outline diagram, flows in Ladugården Biskops Arnö
Exhaust air via stack ventilation,
which in the summer is fan-assisted
Air intake via vent
convectors
Air intake to the lecture hall via a heat
chamber, so-called calorifère
The new exhaust air shafts as well as the attic joist floor are insulated. In this way, insulation of the roof was avoided, as it
has protection orders and may not be altered.
Ventilation in historic buildings
45 ( 60)
6. Landshövdingens stall
Uppsala
History
In the early 1800s, this stable was constructed for
the visitors of the county governor in Uppsala who
came by horse and carriage. There was also space
here for several cows. From the early 1900s the
building has mostly been unused, but it has also
been used as a storage place.
Renovation
The stable was in very bad condition before the
renovation. It had not been maintained and was
partially fire-damaged. When the National Property Board Sweden had found a suitable ­tenant,
the renovation was initiated.
Ventilation was done through cross-ventilation
and gaps in walls, doors and windows.
Conditions for renovation of the ventilation system
With a new operation in the building, another ventilation method was necessary. To comply with the
property’s historic building status, the simplest
type of ventilation system possible was preferred.
This could make the renovation less expensive
and still the tenant could easily ensure that the
building would have an acceptable and suitable
air exchange. Since the building has a heavy brick
frame and high ceilings, stack ventilation is a
good solution.
Ventilation before the renovation
This stable was exactly like the majority of other
stables; without a heating and ventilation system.
Welcome to Pelle Svanslös Hus.
Ventilation in historic buildings
46 ( 60)
The fan can be turned on by the tenant
when the stack effect is not sufficient,
for example, when it is hot outside. When
the fan is started, the hoods for the
natural ventilation close automatically
otherwise air is drawn in that way.
Conservation principles
When the building was going to be renovated and
get heating there was a problem due to the fact
that the base of the roof was totally built together
with the roof. Drilling holes in the base of the
roof was not possible due to the protection orders.
Since ventilation of the roof is absolutely necessary, the problem had to be solved in another way.
Thanks to the fact that the roof had been renovated
in modern times, autorization could be given to
lift the entire roof truss to create a gap between
the base of the roof and the facade. ­T he building
has never been furnished and the interior design
was done in such a way that it is reversible. The
building can easily be adapted to another tenant.
Owners
Always owned by the state. Since 1993,
National Property Board Sweden
The building has two chimneys for stack ventilation with dampers that can be opened and closed as needed. The location and
opening time of the dampers are regulated manually with a
timer operated by the tenant when extra ventilation is needed.
The dampers are closed automatically when the adjacent
exhaust air fan is put into operation.
Tenants
Stable operations ceased in the early 1900s
and after that the building was only used as
a storage space until the National Property Board Sweden found a new operation, the
fairyland museum for the local celebrity,
Pelle Svanslös.
State-owned listed building
The building has been listed as a state-owned
historic building since 1993 and is subject to
protection orders, which state that alterations to the building’s structure may not be carried
out without the authorization of the Swedish
National Heritage Board.
Ventilation in historic buildings
The building still has its original exterior with its transport
bridge at the rear. The kitchen fan, on the far right, can increase the air flow when needed. Close by, you can see one
of the buildings two bathroom fans. They are in operation
24-hours a day in the summer and during the museum’s
open hours in the winter.
47 ( 60)
Ventilation after renovation
The building has stack ventilation. In the summer,
when the stack effect is insufficient, exhaust air
fans can be turned on when needed. Bathrooms
and kitchens have exhaust air fans for continuous operation.
Intake air
Windows and doors have trickle ventilators to
achieve background ventilation. Air is also drawn
in via vent convectors that provide pre-heating in
the winter. Apart from that, ventilation is done by
the tenant opening doors and windows.
exhaust air fan. It is also controlled by a timer. In
this way, the tenant can choose to increase the
exhaust air if needed.
Experiences
The ventilation system is simple to manage and
the tenant has received oral and written instructions. However, on hot summer days the heat can
be extreme. Despite the fact that preparations
for the installation of a cooling system have been
made, the tenant does not think that it is necessary. Another way to cool the building would be to
arrange increased air flow at night.
Exhaust air
The two bathrooms and kitchen all have separate
exhaust air ducts connected to fans on the roof for
continuous operation. In general, the building has
adjustable exhaust air that the tenant regulates.
On the roof, there are two newly-built hoods that
function as chimneys for stack ventilation with
dampers that can be opened. The tenant controls
the opening of the dampers with a timer. Also,
there is an additional hood on the roof with an
Outline diagram, flows in Landshövdingens stall
Exhaust air via stack ventilation, which
in the summer is complemented with an
exhaust air fan
Background ventilation via
bathrooms fans
Outdoor air via trickle
ventilators and crossventilation via opening
windows and doors
Ventilation in historic buildings
It is necessary to continuously inform the tenant about how
the ventilation is designed to work. Here, a piano has been
placed in front of the intake air vent.
48 ( 60)
7. Södra Banco
Gamla Stan, Stockholm
History
In the middle of the 1600s, the townsmen and
council decided that a Bank of Sweden should be
constructed adjacent to Järntorget in Gamla Stan
(Old Town) in Stockholm. Architect, Nicodemus
Tessin the elder was given the assignment to be
responsible for the con­struction of northern
Europe´s first banking building. The building was
nearly completed in 1680 and the Bank of Sweden
moved in. After that, construction continued and
the building was completed in 1712, first by Tessin
the elder and then his son, Tessin the younger.
In 1730, architect Carl Hårleman, was commissioned to carry out an extension to the building,
which was completed in 1737. The property then
stretched from Järntorget down to Skeppsbron
and has been used as offices ever since it was
first built.
The entrance hall to Södra Banco is open for the public.
Owner
Always owned by the state. Today National
Property Board Sweden
Tenants
• The Bank of Sweden 1668–1906
• Museum, achives and offices
• National Property Board Sweden since 1994
State-owned listed building
The building has been listed as a state-owned
historic building since 1935 and is subject to
protection orders, which state that alterations to the building’s structure may not be carried
out without the authorization of the Swedish
National Heritage Board.
Södra Banco has two court-yards.
Ventilation in historic buildings
49 ( 60)
Foundation reinforcement and renovation
In 2003–2004, Södra Bancohuset underwent
extensive foundation reinforcement. The tenant,
SFV, had to move out during this time. A major
­reinforcement operation of the foundation and
masonry work from the 17th and 18th centuries
was required to stabilise the building. In 20042005, an extensive renovation was carried out
and the ventilation system was also adapted to
today´s requirements for good indoor climate.
Ventilation before the renovation Södra Bancohuset was previously stack ventilated, where air with the help of temperature differences, rises out via vents or tiled stoves, the stack
effect. Replacement air, (outdoor air), was drawn
in through leakage between window frames and
window casements. This could create draughts
in winter and no ventilation at all in summer.
In addition, there were many rooms that lacked
exhaust air vents or tiled stoves. Rooms facing
south were very hot in the summer. The majority
of windows could be opened, which was utilized
in the summer, but not everywhere in the building
due to noise disturbance from traffic. The stack
ventilation was insufficient since the existing flues
were not tight due to the settlement damage that
the building had suffered. They were also partially
filled with soot and mortar. The wet areas were
fitted with exhaust air fans. Unfortunately these
fans drew air from flues in nearby rooms, whose
exhaust air thus stopped functioning.
Conditions for renovation of the
ventilation system
The building was constructed using that period´s
construction techniques with thick stone and
brick external walls and with a layout designed
in accordance with that time´s architectural ideal
with rooms opening into each other – enfilade –
and with generous room areas and ceiling heights.
Therefore the air exchange rate does not have to
be as high as in newly constructed buildings with
smaller room volumes.
Conservation principles
With the installation of the new ventilation system
the greatest possible consideration was given to
the building´s protection orders and the requirement not to touch the frame of the building. By
restoring the original flues, the building can be
ventilated without visible installations. Authorization was given to drill holes in the chimneys
The western inner courtyard provides the main stairway with
outdoor air. Behind the air intake grille there is a supply air
unit which purifies the air and pre-heats it during winter.
Ventilation in historic buildings
50 ( 60)
in order to install propeller fans for exhaust air.
Installation of new ventilation grilles in existing, previously sealed windows facing the inner
courtyards (for intake air), and the disassembly
of existing internal windows in the main stairway
in order to access air flow up in the stairway, was
also permitted. Certain rooms had clogged exhaust air vents in the brick flues and these were
restored. By placing the exhaust air fans in the
chimneys in the attic, the need for walkways and
ladders to the roof was minimized and through
that, additions to the building´s ­protected exteriors have been avoided. Fitting the facades facing
the south and west with awnings was possible
since the building had been previously fitted with
such. During the 1800s, awnings were commonly
used to help lower the indoor temperature during
the summer. Therefore, the installation of a cooling unit for the entire building was not necessary.
Through the new-produced ventilation grille the supply air
unit distributes fresh air into the main stairway.
Ventilation after the renovation
All floors and half of the fitted attic floor have
a ventilation system with controlled supply air.
During summer, the exhaust air is mechanically
controlled and during the winter rises thermally
via the stack effect. The part of the attic floor
that faces south, and can be very hot during the
summer, now has a separate mechanical supply
and exhaust air system with cooling and heat
­recovery. The unit is located in a plant room in
the upper attic.
Supply air Replacement air is no longer drawn in via the
windows, and due to this there are no unpleasant
draughts, polluted air or disturbance from traffic.­
Naturally, the windows can be opened if you
want extra ventilation during the summer. ­­In the
basement, which is on the same level as the
inner courtyards, two supply air units have been
installed. These units are located next to the
building´s two stairways. The units, which contain
Via the stairways fresh air rises and provides all floors with air.
Ventilation in historic buildings
51 ( 60)
filters, heating batteries and fans with silencers,
get their air from the courtyards and blow it into
the stairway. The air from the courtyards is less
polluted than that on the street side. Since the
building has a somewhat open design without
closed doors, every room can be given the necessary volume of air via stairways and corridors.
Those rooms that often must have closed doors
have been provided with transfer air slots in the
door frames, or silenced transfer air devices. The
flow of the supply air fans is controlled by a pressure sensor on the 4th floor to ensure negative
pressure in the building.
Behind the exhaust air grilles, control valves have been
mounted to adjust the flow of exhaust air. This ventilation
grille has been recycled. It was saved from a previous
alteration at the Manilla school in Stockholm.
Exhaust air
After the survey of the building´s 17 clay brick
chimneys (with a total of 66 flues) it was noticed
that there were flues enough to equip every room
with vents for exhaust air. In some rooms new
holes were made in previously unutilized flues.
All flues were then cleaned and sealed. The original exhaust air grilles have been retained. They
are cleaned and re-painted. The existing plastic
grilles were replaced with new grilles similar to
the originals. Some grilles come from a previous
renovation of the ­Manilla school. Since the existing exhaust air flues have regained their original
function, the ventilation in the winter can function
with the stack effect. To ensure the flow of air in
the summer, every chimney has been fitted with
a rotational frequency controlled fan (pro­peller
fan), in the attic. The fans shall only be in operation during the warmer parts of the year when
stack ventilation ceases and will be regulated so
that the right flow is obtained. The fans are not in
use in winter. They provide virtually no resistance
when turned off and therefore do not counteract
the stack effect. Since the fans in the chimneys
are jointly used for all flues in each chimney, all
exhaust air vents in the rooms have been fitted
with (hidden) control valves to adjust the air flow.
Wet areas are connected to exhaust air fans which
The tiled stove in the Session hall has been fitted with an exhaust air grille on the top. A carbon dioxide indicator speeds
up the exhaust air automatically when needed.
Ventilation in historic buildings
52 ( 60)
Thanks to sunlight-and weathercontrolled awnings, no cooling
unit is needed. Södra Banco,
Stockholm.
are in operation year-round during the daytime.
The assembly hall (the Session Hall) is fitted with
an exhaust air fan whose flow is controlled by
the carbon dioxide content. The carbon dioxide
content is also measured centrally on a continuous basis from the 5th floor.
Experiences
The property´s tenants are satisfied with the new
ventilation system. The air is perceived as pleasant. The sunlight-and weather-controlled awnings
and the extra night cooling, when needed, give
a good indoor climate even in the summer. The
tenants have no problem with adapting to the
building´s conditions. It is important that no more
workplaces are set up than the room´s ventilation
is dimensioned for. Those who work here must
be aware that if the door to a room is shut, the
ventilation decreases. When using the assembly
hall and meeting rooms, meetings should be held
with intermittent breaks for opening doors and
windows. When stairways and corridors are used
for supply air, as they are in this building, it is very
important to have efficient and thorough cleaning
so dust and dirt is not spread around. After the
building´s new ventilation system had been in use
for a year, it was discovered that decayed mortar
had sometimes loosened and fallen on the axial
fans and caused interruption of service. Experience has shown that the flues above the fans
must also be sealed.
Outline diagram, flows in Södra Banco
Exhaust air fans in
operation during
the summer
Supply air
distributed
via stairways and
corridors
Exhaust air via
existing brick flues
Pressure controlled supply
air units
Air inlet from the courtyards
Ventilation in historic buildings
53 ( 60)
8. Thielska galleriet
Djurgården, Stockholm
History
Between 1904-07 financier, Ernest Thiel, constructed a palace for himself and his family on
Eol’s kulle (Eol’s Hill), Blockhusudden’s highest
point on Djurgården. The architect was Ferdinand
Boberg. Thiel was a major collector of contemporary art and his palace became one of Stockholm’s
most beautiful Art Nouveau buildings.
Renovation
The building underwent a major renovation in
the early 1930s in order to better adapt to the
museum operation. A new apartment for a curator
was furnished in the western part of the building.
In the mid-1960s, the facades were re-plastered
with grey and defective plaster. In the 1970s the
walls in the exhibition halls were covered with
fibreglass weave, painted with semi-gloss plastic
paint, and fluorescent lighting was installed in
the ceilings. The building underwent a restoration
in different phases between 1999-2004. Then
­facades once again got a smooth and white plaster and the exhibition hall walls were filled and
painted in a light grey tint to resemble the wool
fabric that originally covered the walls. In connection with the facade renovation, a re-utilized oldstyle ventilation grille was mounted on the entry
facade to cool the Munch Exhibition Hall.
Ventilation before the renovation
The building was originally constructed with a
calorifère system for ventilation. The exhibition
Owners
The palace was owned by Ernest Thiel until 1924 when the Swedish state purchased the building, including his entire art collection. Today, the building is owned by the National Property Board Sweden.
Tenants
The palace was a private residence until 1924. Thielska Galleriet opened to the public in 1926 and is still currently a museum with the most complete collection of the last century’s Nordic artists and includes works by Edvard Munch, Anders Zorn, Bruno
Liljefors, August Strindberg and others.
Thielska galleriet is located on Eol’s kulle on southern
Djurgården.
Ventilation in historic buildings
54 ( 60)
halls were ventilated with air that is pre-heated in
a heat chamber in the cellar and distributed via
sheet metal and brick ducts. The domestic part of
the building uses stack ventilation. Over time, the
ducts had become clogged with leaves and dust.
The ventilation functioned poorly. The Munch Hall,
which is provided with daylight through a lantern,
was very hot in the summer because the lantern
was poorly ventilated.
Conditions for renovation of the
ventilation system
The building is unique and the art requires a certain indoor climate in order not to be damaged.
Installing a modern and visible ventilation system
was not possible. The ambition has been to repair
the old system and complement it with installations that do not impact the architecture of the
building.
A close-up view of the roof to the Munch Hall with exhaust
air hoods, and further away, the cupola. The small photo
shows the cupola’s exhaust air opening.
Conservation principles
In 1993 the building was protected by a preservation order stating that neither internal nor
external alterations to the building's original appearance may be carried out without the authorization of the Swedish National Heritage Board.
The renovation between 1999 and 2004 involved
restoring the building's internal and external
finishes. Authorization was granted to mount a
re-used old-style intake air grille on one of the
facades.
State-owned listed building
The building has been listed as a state-owned
historic building since 1993 and is subject to protection orders, which state that alterations to the
building’s structure may not be carried out without
the authorization of the Swedish National Heritage
Board.
The exhibition halls in Thielska galleriet are ventilated by the
building’s calorifère system.
Ventilation in historic buildings
55 ( 60)
Here, air is taken into the calorifère chamber. The damper
can be positioned manually for the desired air flow.
Ventilation after renovation
The building’s calorifère system was retained and
given better functionality by cleaning the intake air
ducts. In this way the original function of the ventilation was restored. Despite this, the Munch Hall,
with its lantern, was too hot in the summer. To
solve this problem, a duct fan was installed in an
unused brick duct, which was further connected to
a new sheet metal duct, debouching in the lantern.
A new intake air grille was mounted in the brick
duct at the ground floor in the museum’s entry
­facade, which faces north. In this way, cool air is
pressed into the ­lantern, which is then ventilated
through the stack effect via roof hoods.
Intake air
The building has two different systems for bringing
outdoor air into the rooms. The large exhibition
halls gets the air, which in winter is pre-heated, via
the heat chamber that is part of the building’s calorifère system. Through brick ducts the air rises into
the exhibition halls via grilles mounted high on the
walls. In the domestic part of the building, the
outdoor air is drawn in through vents and gaps
between the window casements and frames.
In the heat chamber, the air is heated by radiators that are
mounted in the ceiling.
Ventilation in historic buildings
The Munch Hall’s lantern is now cooled with outdoor air that
is drawn in through this newly installed grille, which is re­
cycled from a previous renovation at the Manilla school.
56 ( 60)
Exhaust air
All rooms have exhaust air through stack ventilation via brick flues. The lanterns above the large
halls are also ventilated by the stack effect, using
hoods.
Experiences
The calorifère system functions poorly in the summer. Initially, installation of a fan in the heat chamber was planned but never carried out. If this was
done now, it would possibly provide more effective cooling for the exhibition halls. Cooling of
the Munch Hall has been improved through the
measures that were taken.
Exhaust air grille in the cupola room. In 1978, Karl Axel
Pehrson added this decoration to the cupola.
Outline diagram, flows in Thielska galleriet
Exhaust air via brick
flues
Lantern
Heated air from the heat chamber is distributed upwards in
the building through brick ducts.
New duct
fan for the
cooling of
the Munch
Hall’s
lantern
Air intake
via a heat
chamber;
so-called
calorifère
The lantern above the Munch Hall is cooled by cool air in the
summer.
Ventilation in historic buildings
57 ( 60)
Glossary
Axial fan = propeller fan
Background ventilation = the lowest air exchange
(ventilation rate) in a room
Ceiling fan (Casablanca fan) = fan mounted in
the ceiling used to even out temperature differences in the room
Climate cooling = cooling unit that cools the room
to a comfortable temperature
Conservation plan = describes conservation
­requirements of the property and long-term
goal for the preservation and management of
the building
Control valve = an exhaust air terminal device for
adjusting the air flow. It can be mounted in an
exhaust air vent, to obtain the adequate volume
of exhaust air from a room into the flue or duct
Cooling baffle = a chilled beam, containing a cooling battery, using water to remove heat from a
room
Cowl = a sort of chimney cap that turns round with
the wind so as to present its opening to the
leeward and therefore creates negative pressure in the flues. It increases the stack effect
Damper = device for adjusting the air flow
Draught = unpleasant air movement
Ductwork = composite system of ventilation
ducts
Emissions = gases that are emitted by paint,
furniture, etc
Exhaust air = used air that is conveyed outside
mechanically or via the stack effect
Exhaust air device = is used to carry air from a
room
Exhaust air system = system where the exhaust
air flow is controlled by a fan
Fan air-heater/cooler = battery in the ventilation
system used to heat or cool air
Ventilation in historic buildings
Fan-assisted stack ventilation = during the varm
part of the year, when the stack effect ceases,
the exhaust air is governed mechanically.
Fan coil (fan convector) = device equipped with
fan and heating and/or cooling battery intended
to climate-adapt a room
Fan ventilation (mechanical ventilation) = ventilation with the help of fans
Heat exchanger = device used to transfer heat
between exhaust and intake air
Heating plant room = space for technical equipment for heating
Heat pump = heating device that utilizes the free
energy that exists in, for example, exhaust air,
outdoor air, water or the ground
HVAC = heating, ventilation, air-conditioning
Increased air flow = largest air flow (ventilation
rate) in a room (in the event of increased heat or
a large number of people)
Intake air = external air that is conveyed into a
room or into a supply air unit
Intake- air radiator = specially designed radiator
with an air-inlet that pre-heats outdoor air
Installation system = heating, cooling or ventilation system
LCC (Life Cycle Cost) = the concept includes both
the investment and operation costs during a
system’s lifetime
Night cooling = cooling of rooms at night with
the help of cooler outdoor air via mechanical or
natural ventilation
Operating time = time when the system is in
operation
Outdoor air = external air, outside air
OVK = obligatory ventilation inspection according
to Swedish legislation
58 ( 60)
Radial fan = Fan with wheels that rotate in a shellformed capsule and draws in air axially and
throws it out radially; also called a centrifugal
fan
Replacement air = make-up air, the required volume of air supplied into a room, compensating
for the same volume of exhausted air, extracted
mechanically or via the stack effect
Reversible installation = installation that can be
removed without leaving major marks in the
building frame
Ridges = upper part of the attic above the truss
ties
Rotating heat exchanger = heat exchanger consisting of a rotor, equipped with air ducts, which
passes alternatively through the exhaust and
intake air flows to transfer heat
Slotted vent = an intake air device for providing
outdoor air into a room
Stack effect = is the movement of air. When there
is a temperature difference between two adjoining volumes of air, the warmer air will have
lower density and be more buoyant thus rising
above the cold air creating an upward air stream
driven by buoyancy
Stack ventilation = natural ventilation that functions without the help of fans due to the temperature difference between two adjoining volumes
of air. Warmer air has lower density and is thus
more buoyant and rises above colder air,
creating an upward air stream
Supervisory authority = authority whose task it
is to ensure that laws and provisions that fall
within the authority’s area of operations are
adhered to
Supply air device = is used to provide air to a
room
Ventilation in historic buildings
Supply and exhaust air system = system where
both the exhaust and supply air flows are
controlled by fans, often called a balanced
ventilation system
Timer = device used for timing
Transfer air device = device, mounted in a wall between two rooms to distribute air
Transferred air = air that is carried from one room
to another
Transom = horizontal frame/beam that separates
the upper ventilation casement from the lower
casement in a window
Trickle ventilator = an intake air device, fitted to
a window casement or frame, for providing outdoor air into a room
VAV-system = supplies variable volume of conditioned air for heating, ventilating, and/or airconditioning
Ventilation = movement of air into or out of
a space, to provide fresh air, to carry away
­moisture, odours or dangerous gases or to allow
free flow in drains
Ventilation flow = air volume per unit of time;
often measured in litre per second, l/s
Vent convector = wall-mounted device equipped
with a heat battery for providing pre-heated
outdoor air
59 ( 60)
Ventilation in historic buildings
60 ( 60)
national cultural history. Each one is part of the nation’s history and its future.
The National Property Board aims to make all Swedes proud of these national treasures –
palaces and royal parks, theatres, museums, embassies, and property comprising one seventh
of the total land mass of Sweden. All are owned by the Swedes collectively, and the duty of the
Board is to administer them in the best possible way.
Our task is not only to maintain the soul and character of each building, but also to adapt
them to present day needs and uses for the benefit and enjoyment of tenants and the general
public alike. Just as important as passing on the history behind existing buildings is the creation
of new buildings worthy of the future. We are therefore commissioned by the Swedish government to carry out new building projects which in various ways are representative of our nation.
We also administer state-owned forests and land in a sustainable manner so as to preserve
bio diversity and maintain reindeer pasture lands for the benefit of future generations.
National Proper ty Board Sweden +46 8 696 70 00 www.sf v.se
Design: Dick Norberg. All illustrations: Helena Adolphson (p. 40, Bo Hyttring). All photos: Helena Adolphson ( p. 1, 55, lower photo and inside covers: Dick Norberg. p.3, left photo and p.40: C G Hellgren) Copyright © 2009 National Property Board Sweden. Printing: Intellecta Infolog AB, 2009. Cover photo: Gamla riksarkivet, Riddarholmen, Stockholm.
Tradition is change. Sweden has many buildings and environments of great value to its