building promoter: probam nv architect: declercq e. the keppekouter project design issue design...

Building promoter: PROBAM nvBuilding promoter: PROBAM nv

Architect: Declercq E.Architect: Declercq E.

Building promoter: PROBAM nvBuilding promoter: PROBAM nv

Architect: Declercq E.Architect: Declercq E.

The Keppekouter project

Design issueDesign issue

Major findingsMajor findings

Keppekouter Keppekouter buildingbuilding

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Monitoring Monitoring resultsresults

Building Building presentationpresentation

Summer Summer comfortcomfort

Indoor Air Indoor Air QualityQuality

Building conceptBuilding concept

Low heating Low heating consumptionconsumption

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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)

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)

Building presentation (1...)

PHASE 1PHASE 1 PHASE 2PHASE 2 PHASE 3PHASE 3

N

4.500 m² office area 700 m² 4.500 m² office area 700 m² cellar areacellar area

4.500 m² office area 700 m² 4.500 m² office area 700 m² cellar areacellar area

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Building presentation (2|)

Building under construction…Building under construction…Building under construction…Building under construction…

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The design issue (1...)

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.

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.

Brussels

Oste

nd

< 100m

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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 ??

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 design issue (2|)

Highway Brussels-OstendHighway Brussels-OstendHighway Brussels-OstendHighway Brussels-OstendKeppekouter projectKeppekouter projectKeppekouter projectKeppekouter project

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The concept had three main targets: 1. Low energy use in winter time 2. Thermal comfort in summer 3. Good indoor air quality during office hours

1. Low energy use in winter time The building is well insulated (compared to Belgian office buildings) to

reduce the transmission losses :– 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 concept had three main targets: 1. Low energy use in winter time 2. Thermal comfort in summer 3. Good indoor air quality during office hours

1. Low energy use in winter time The building is well insulated (compared to Belgian office buildings) to

reduce the transmission losses :– 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 (1…)

1. Low energy use in winter time

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The building concept (2…) 2. Thermal summer comfort

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.

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.

REDUCTION of GAINS:REDUCTION of GAINS: indirect solar gainsindirect solar gains direct solar gainsdirect solar gains

internal gainsinternal gains

REDUCTION of GAINS:REDUCTION of GAINS: indirect solar gainsindirect solar gains direct solar gainsdirect solar gains

internal gainsinternal gains

FREE-COOLING & FREE-COOLING & STORAGE:STORAGE:

night ventilation & night ventilation & thermal massthermal mass

FREE-COOLING & FREE-COOLING & STORAGE:STORAGE:

night ventilation & night ventilation & thermal massthermal mass

GLOBAL STRATEGY for GLOBAL STRATEGY for thermal comfort under thermal comfort under

summer conditionssummer conditions

GLOBAL STRATEGY for GLOBAL STRATEGY for thermal comfort under thermal comfort under

summer conditionssummer conditions

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insulationthickness (cm)

U-value g-value solar gainsin comparison with

roof with 3 cm insulation3 cm 1,02 W/m²K 4,4 % 100 %5 cm 0,68 W/m²K 2,9 % 66 %

10 cm 0,37 W/m²K 0,37 % 36 %15 cm 0,25 W/m²K 0,25 % 25 %

g-value=X/YY

X

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

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


Reduction of gains - indirect solar gains

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very large very large transparent transparent

surfacessurfaces

very large very large transparent transparent

surfacessurfaces

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In order to achieve thermal comfort it is essential to limit the direct solar gains, especially when the window surfaces are large

In order to achieve thermal comfort it is essential to limit the direct solar gains, especially when the window surfaces are large


Reduction of gains - direct solar gains

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In this project, this is achieved by the following measures : 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

In this project, this is achieved by the following measures : 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 Vertical external external screensscreens

Vertical Vertical external external screensscreens

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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.

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.



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Office 1 Office 3

Office 4 Ext.

Importance of solar protection: office 3 has one window without

external screen

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Reduction of gains - internal gains

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 )

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 )

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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.

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.


Night Ventilation - first concept

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.) 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

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.) 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

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mechanical ventilation (roof fan: mechanical ventilation (roof fan: 4.300m³/h 4.300m³/h 6,5vol./h) 6,5vol./h)

mechanical ventilation (roof fan: mechanical ventilation (roof fan: 4.300m³/h 4.300m³/h 6,5vol./h) 6,5vol./h)

natural ventilation (cross-natural ventilation (cross-ventilation)ventilation)

natural ventilation (cross-natural ventilation (cross-ventilation)ventilation)

Final solution without loss of rentable space:

The top-floor is mechanically ventilated by means of a roof fan

The ground and the first-floor are naturally ventilated (cross-ventilation)

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).

Final solution without loss of rentable space:

The top-floor is mechanically ventilated by means of a roof fan

The ground and the first-floor are naturally ventilated (cross-ventilation)

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).


Night Ventilation - final concept

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Night Ventilation - final concept - components: inlet openings

Removable burglar-proof Removable burglar-proof ventilation grilles in combination ventilation grilles in combination

with slide windowswith slide windows

Removable burglar-proof Removable burglar-proof ventilation grilles in combination ventilation grilles in combination

with slide windowswith slide windows

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Night Ventilation - final concept - components: roof fan

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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: 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.

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: 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.


Night Ventilation & Thermal mass

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semi-open false ceilingsemi-open false ceilingsemi-open false ceilingsemi-open false ceiling


Night Ventilation & Thermal mass - false ceiling

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False floor construction: two layers of gypsum board on metal frame and adjustable supports thermal mass not accessible

False floor construction: two layers of gypsum board on metal frame and adjustable supports thermal mass not accessible


Night Ventilation & Thermal mass - false floor

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air supply deviceair supply deviceair supply deviceair supply device

The indoor air quality in this building is guaranteed by a system of mechanical ventilation.

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.

The indoor air quality in this building is guaranteed by a system of mechanical ventilation.

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 RecoveryHeat RecoveryHeat RecoveryHeat Recovery

The building concept (15…) 3. Indoor Air Quality

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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

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

The building concept (16|) 3. Indoor Air Quality

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Monitoring results (1…)

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:

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.

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:

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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Office without solar Office without solar protection...protection...

Office without solar Office without solar protection...protection...

Monitoring results (2|) summer monitoring

More about monitoring:

ACH

monitoring set-up...

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Major Findings 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: 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 The problems of too cold indoor temperatures in the morning could be

avoided by controlling the night ventilation automatically.

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)

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: 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 The problems of too cold indoor temperatures in the morning could be

avoided by controlling the night ventilation automatically.

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...

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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

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

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

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

building promoter: probam nv architect: declercq e. the keppekouter project design issue design...

Documents

building promoter

building monitoring

summer time

construction slide

cellar area slide

low energy use

office area

property developer