The Keppekouter project
Keppekouter
building
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
Major findings
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Building promoter: PROBAM nv
Architect: Declercq E.
Building presentation (1...)
Keppekouter
building
Building
presentation
Design issue



Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
The project was constructed by property developer in Aalst, close to the highway
between Brussels and Ghent. The project consists of three similar office buildings.
Each building has three floors and a cellar.
The overall cost of project was important.
The office area is let by the developer,with the result that this context has some
specific characteristics:


The future occupants (and his needs and wishes) are not known.
A good indoor climate and a low energy use is a direct benefit for the tenant (not for the
developer)
4.500 m² office area 700 m²
cellar area
N
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PHASE 1
PHASE 2
PHASE 3
Building presentation (2|)
Keppekouter
building
Building
presentation
Design issue
Building concept
Low heating
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Summer
comfort
Indoor Air
Quality
Monitoring
results
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Building under construction…
The design issue (1...)
Keppekouter
building
Building
presentation
Design issue
< 100m
Building concept
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comfort
Indoor Air
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
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Some of the potential tenants wanted openable windows to prevent overheating in
summer time. Given the nearby highway, it was clear that such strategy would lead to
noise problems as illustrated by the picture on next slide.
Discussions with the developer resulted in the decision to aim for good indoor climate
conditions (temperature, IAQ,…) without openable windows at working hours and
without active cooling.
The design issue (2|)
Keppekouter
building
Keppekouter project
Highway Brussels-Ostend
Building
presentation
Design issue
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

DESIGN ISSUE:
Free-cooling in summer time by opening windows not
possible: acoustical problems !!
How to create an acceptable summer indoor climate
without an expensive cooling installation ??
The building concept (1…)
1. Low energy use in winter time
Keppekouter
building
Building
presentation



Design issue

Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
The concept had three main targets:

1. Low energy use in winter time

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The building is well insulated (compared to Belgian office buildings) to
reduce the transmission losses :
–
–
–
–
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1. Low energy use in winter time
2. Thermal comfort in summer
3. Good indoor air quality during office hours

aluminium window frames with thermal break
glazing: U-value = 1,5 W/m²K
4 cm insulation in vertical walls
10 cm insulation in roof construction
The ventilation losses are reduced by a heat-recovery installation in
the ventilation system (see Chapter ‘good indoor air quality’)
The building concept (2…)
2. Thermal summer comfort
Keppekouter
building

Building
presentation
Design issue

Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
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As explained before, the main design issue in this project is the thermal summer
comfort. Due to the highway nearby, windows can’t be open during summer time. So
free-cooling is not possible and without special measures there is a high risk of
overheating.
The risk of overheating is in this building strongly reduced by several measures (see
following slides). It has to be stressed that an acceptable indoor climate only can be
achieved by the combined effect of all these measures.
GLOBAL STRATEGY for
thermal comfort under
summer conditions
REDUCTION of GAINS:
indirect solar gains
direct solar gains
internal gains
FREE-COOLING &
STORAGE:
night ventilation &
thermal mass
The building concept (3…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Reduction of gains - indirect solar gains

Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality

Monitoring
results
Major findings
During warm summer days the radiation of
the sun can be up to 1.000 W/m2. If this
heat flux strikes an opaque surface, a part
of the heat is transmitted by conduction,
convection and radiation to the indoor.
These heat gains are called ‘indirect solar
gains’
The indirect solar gains through the roof of
the buildings are reduced by a insulation of
10 cm PUR. The influence of this measure
is given in the table below
insulation
thickness (cm)
U-value
g-value
3 cm
5 cm
10 cm
15 cm
1,02 W/m²K
0,68 W/m²K
0,37 W/m²K
0,25 W/m²K
4,4 %
2,9 %
0,37 %
0,25 %
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g-value=X/Y
solar gains
in comparison with
roof with 3 cm insulation
100 %
66 %
36 %
25 %
X
Y
The building concept (4…)
2. Thermal summer comfort
Keppekouter
building
Reduction of gains - direct solar gains
Building
presentation
Design issue
In order to achieve thermal comfort it is essential to limit the direct solar
gains, especially when the window surfaces are large
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
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very large
transparent
surfaces
The building concept (5…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Reduction of gains - direct solar gains


Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
In this project, this is achieved by the following measures :


Monitoring
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selective glazing, with high light transmittance (67%) but low solar gains
transmittance (36* %)
vertical screens are used which are controlled by a meteo station and wind
detector (see picture)
Technical data :


shading open : g = .36
shading closed : g = 0.10
Vertical
external
screens
The building concept (6…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Reduction of gains - direct solar gains

Design issue
Building concept
The importance of the reduction of the direct solar gains can be illustrated by
measurements during some days of September ‘97:
All offices are equipped with external screens, except Office 3. This office has one
window without an external screen.
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Major findings
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30
25
temperature (°C)
Monitoring
results
35
20
15
Importance of solar protection:
office 3 has one window without
external screen
10
5
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0
22/8/97
23/8/97
24/8/97
25/8/97
date
NatVent
Office 1
Office 3
Office 4
Ext.
26/8/97
27/8/97
The building concept (7…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Reduction of gains - internal gains

Design issue

Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
Major findings
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Lighting is one of the most important internal gains in office buildings (often
up to 30% of all internal gains and more).
In this building the heat gains from lighting are minimised by


using modern luminaries with high frequency ballasts. One can achieve 400 lux
levels with only 8…10 W/m² of installed power. (Classical designs may represent
a thermal charge of up to 20…25 W/m².)
further reductions of the lighting gains are obtained by making use of daylight
compensation
– The lamps close to the windows are equipped with a sensor. This sensor measures the
lux-level on the plane under the lamp. The artificial light is dimmed as function of the
measured lux-level
– This technique leads to lower internal gains and a lower energy consumption (average
load of the artificial lighting of 5 to 6 W/m² )
The building concept (8…)
2. Thermal summer comfort
Night Ventilation - first concept
Keppekouter
building
Building
presentation

Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality


Monitoring
results
Major findings

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Night ventilation aims to cool down the building
mass. This requires rather high air change rates
of cold external air at night time (a multiple of
the air flows needed for IAQ control).
In this project, the air is supplied through large
louvres which are installed in front of several
windows.
A first idea was to extract the air with chimneys
which means that ventilation flows are driven by
stack effect. However in this project this concept
was not acceptable because of the loss of
rentable space.
Chimney concept:

Cold external air is supplied through ventilation louvres in the façade

The air is extracted through chimneys. (The stack effect is proportional to the
difference in height. Therefore the sections of the chimneys vary.)
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The disadvantage with this approach is:

Each chimney is a loss of rentable space: not acceptable due to the economic
context of a building promoter
The building concept (9…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Night Ventilation - final concept

Design issue
Final solution without loss
of rentable space:

Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
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

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mechanical ventilation (roof fan:
4.300m³/h  6,5vol./h)
The top-floor is
mechanically ventilated
by means of a roof fan
The ground and the firstfloor are naturally
ventilated (crossventilation)
In practice:

All internal doors have to
be open at night. As the
minimal rent-unit in this
building is a half floor,
there are no problems
with this approach
(security and privacy).
natural ventilation (crossventilation)
The building concept (10…)
2. Thermal summer comfort
Keppekouter
building
Night Ventilation - final concept - components: inlet openings
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
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Removable burglar-proof
ventilation grilles in combination
with slide windows
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The building concept (11…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
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Night Ventilation - final concept - components: roof fan
The building concept (12…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Night Ventilation & Thermal mass

Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results

Night ventilation is not viable without sufficient thermal mass.
In this building rented area is used as open plan office space.
This means that thermal mass is only available in floors and
ceilings.
Offices usually have false ceilings because:




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offers a lot of flexibility for cabling, HVAC and lighting
is cheap (cheaper then a plastered or painted ceiling)
However it is clear that a false ceiling reduces dramatically
the available thermal mass.
In this case, a compromise was found by using a semi-open
false ceiling. This solution is a cost effective measure and
was therefore acceptable for the building promoter (economic
context of the project!).
The accessibility of the thermal mass of the floor is very
limited in this building as there is a false floor over the
concrete floor.
The building concept (13…)
2. Thermal summer comfort
Keppekouter
building
Night Ventilation & Thermal mass - false ceiling
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
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semi-open false ceiling
The building concept (14…)
2. Thermal summer comfort
Keppekouter
building
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
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Night Ventilation & Thermal mass - false floor
False floor construction: two layers of gypsum
board on metal frame and adjustable
supports  thermal mass not accessible
The building concept (15…)
3. Indoor Air Quality
Keppekouter
building

Building
presentation
Design issue
The indoor air quality in this building is
guaranteed by a system of mechanical
ventilation.

Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
Major findings
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

The system pulses fresh air in the offices
(30m³/h.person) and extracts air from the
toilettes and the elevator shaft.
The fresh air input is situated on the roof.
The system contains a heat-recovery unit.
Heat Recovery
air supply device
The building concept (16|)
3. Indoor Air Quality
Keppekouter
building
Building
presentation

Design issue
In this project mechanical ventilation for indoor air quality was preferred to natural
ventilation because of the following reasons:

natural air intakes in the façade can imply acoustical problems as there is a
busy highway at 100 m.

mechanical ventilation allows to place the air input on the roof, where the air
quality is acceptable.

mechanical ventilation allows to integrate easily a heat-recovery unit.

as natural air flows depend on weather conditions (wind speed, temperature..)
they are not constant
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
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Monitoring results (1…)
Keppekouter
building

Building
presentation
Design issue

During August & September ‘97 the indoor climate (temperatures, air
flows,...) was monitored during several weeks in four offices on the top
floor of the building (mechanical night ventilation).
Some main conclusions out of the summer monitoring results:
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results

During a hot period the indoor temperature does not exceed the external
temperature on the hottest day.

However offices without external solar protection have problem of overheating

The impact of the night ventilation could be improved by a better accessibility of
the thermal mass

Mechanical night ventilation could be controlled by temperature sensor to avoid
too low indoor temperatures in the morning.
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Monitoring results (2|)
summer monitoring
Keppekouter
building
Building
presentation
35.0
Design issue
30.0
Building concept
Monitoring
results
25.0
temperature (°C)
Low heating
consumption
Summer
comfort
Indoor Air
Quality
20.0
Off.1
15.0
Off.2
10.0
Major findings
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Office without solar
protection...
Off.3
Off.4
Ext.
5.0
0.0
23/8 0
More about
monitoring:
ACH
23/8 12
24/8 0
24/8 12
25/8 0
25/8 12
time
26/8 0
26/8 12
27/8 0
27/8 12
28/8 0
monitoring set-up...
Major Findings
Keppekouter
building

The design of the Keppekouter project is an example of a global
strategy to avoid the problem of overheating in summer time without
active cooling. This concept seems to be compatible with the Belgian
economic context of a building promoter.

However the implementation of some measures could be improved:
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality

The accessibility of the thermal mass in the building is limited. The reasons
are twofold:
– the cost aspect (building promoter)
– the building physics consultant entered only at the end into the building design,
when main options were already taken
Monitoring
results

The problems of too cold indoor temperatures in the morning could be
avoided by controlling the night ventilation automatically.
Major findings
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
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In this project, the indoor air quality is guaranteed by mechanical ventilation as
there were a lot of severe barriers toward natural ventilation:

acoustical comfort (highway near by)

outdoor air quality

energy efficiency (heat-recovery)
More information...
Keppekouter
building
Building
presentation
Design issue
Building concept
Low heating
consumption
Summer
comfort
Indoor Air
Quality
Monitoring
results
Find more information on the PROBE building in the following documents:
\Reports \Monitoring Reports \Summary Reports\be2summ.pdf
 global presentation of the buildings (4p./building)
 contents: building description - ventilation strategy and technology winter and summer monitoring results - conclusions
\Reports \Monitoring Reports \Detailed Reports\be2det.pdf
 detailed reports of all 19 monitoring campaigns (20p./campaign)
 contents: monitoring set up - analysis of results - conclusions
Major findings
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You can read and print pdf-files with the Acrobat® Reader
®3.0. Program. This program is free.
Download it from the Acrobat web site: www.adobe.com OR
run the installation file ar32e301(1).exe in the directory
\Installation