The Keppekouter project - BREprojects.bre.co.uk/natvent/presentation/202_be2.pdf · The Keppekouter project Design issue Major findings ... indirect solar gains direct solar gains

Building promoter: PROBAM nvBuilding promoter: PROBAM nvArchitect: Declercq E.Architect: Declercq E.

The Keppekouter project

Design issueDesign issue

Major findingsMajor findings

KeppekouterKeppekouterbuildingbuilding

MoreMoreinformation...information...

Back toBack to“Select a“Select abuilding”building”

MonitoringMonitoringresultsresults

BuildingBuildingpresentationpresentation

SummerSummercomfortcomfort

Indoor AirIndoor AirQualityQuality

Building conceptBuilding concept

Low heatingLow heatingconsumptionconsumption

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! The project was constructed by property developer in Aalst, close to the highwaybetween 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 m²4.500 m² office area 700 m²cellar areacellar area

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Building presentation (2|)

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 insummer time. Given the nearby highway, it was clear that such strategy would lead tonoise problems as illustrated by the picture on next slide.

! Discussions with the developer resulted in the decision to aim for good indoor climateconditions (temperature, IAQ,…) without openable windows at working hours andwithout active cooling.

Brussels O

stend

< 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 ??

The design issue (2|)

Highway Brussels-OstendHighway Brussels-OstendKeppekouter 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 inthe ventilation system (see Chapter ‘good indoor air quality’)

The building concept (1…)

1. Low energy use in winter time

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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. Sofree-cooling is not possible and without special measures there is a high risk ofoverheating.

! The risk of overheating is in this building strongly reduced by several measures (seefollowing slides). It has to be stressed that an acceptable indoor climate only can beachieved by the combined effect of all these measures.

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

internal gains internal gains

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

night ventilation &night ventilation &thermal massthermal mass

GLOBAL STRATEGY forGLOBAL STRATEGY forthermal comfort underthermal 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/Y Y

X

! During warm summer days the radiation ofthe sun can be up to 1.000 W/m2. If thisheat flux strikes an opaque surface, a partof the heat is transmitted by conduction,convection and radiation to the indoor.These heat gains are called ‘indirect solargains’

! The indirect solar gains through the roof ofthe buildings are reduced by a insulation of10 cm PUR. The influence of this measureis given in the table below


2. Thermal summer comfortReduction of gains - indirect solar gains

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very largevery largetransparenttransparent

surfacessurfaces

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


2. Thermal summer comfortReduction 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



VerticalVerticalexternalexternalscreensscreens

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! The importance of the reduction of the direct solar gains can be illustrated bymeasurements during some days of September ‘97:

All offices are equipped with external screens, except Office 3. This office has onewindow 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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2. Thermal summer comfortReduction of gains - internal gains

! Lighting is one of the most important internal gains in office buildings (oftenup 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 representa thermal charge of up to 20…25 W/m².)

" further reductions of the lighting gains are obtained by making use of daylightcompensation

– The lamps close to the windows are equipped with a sensor. This sensor measures thelux-level on the plane under the lamp. The artificial light is dimmed as function of themeasured lux-level

– This technique leads to lower internal gains and a lower energy consumption (averageload of the artificial lighting of 5 to 6 W/m² )

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! Night ventilation aims to cool down the buildingmass. This requires rather high air change ratesof cold external air at night time (a multiple ofthe air flows needed for IAQ control).

! In this project, the air is supplied through largelouvres which are installed in front of severalwindows.

! A first idea was to extract the air with chimneyswhich means that ventilation flows are driven bystack effect. However in this project this conceptwas not acceptable because of the loss ofrentable space.


2. Thermal summer comfortNight 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 economiccontext 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))

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

! Final solution without lossof rentable space:" The top-floor is

mechanically ventilatedby means of a roof fan

" The ground and the first-floor are naturallyventilated (cross-ventilation)

! In practice:" All internal doors have to

be open at night. As theminimal rent-unit in thisbuilding is a half floor,there are no problemswith this approach(security and privacy).


2. Thermal summer comfortNight Ventilation - final concept

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2. Thermal summer comfortNight Ventilation - final concept - components: inlet openings

Removable burglar-proofRemovable burglar-proofventilation grilles in combinationventilation grilles in combination

with slide windowswith slide windows

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2. Thermal summer comfortNight 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 andceilings.

! 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 dramaticallythe available thermal mass.

! In this case, a compromise was found by using a semi-openfalse ceiling. This solution is a cost effective measure andwas therefore acceptable for the building promoter (economiccontext of the project!).

! The accessibility of the thermal mass of the floor is verylimited in this building as there is a false floor over theconcrete floor.


2. Thermal summer comfortNight Ventilation & Thermal mass

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semi-open false ceilingsemi-open false ceiling


2. Thermal summer comfortNight Ventilation & Thermal mass - false ceiling

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False floor construction: two layers of gypsumboard on metal frame and adjustablesupports → thermal mass not accessible


2. Thermal summer comfortNight Ventilation & Thermal mass - false floor

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air supply deviceair supply device

! The indoor air quality in this building isguaranteed by a system of mechanicalventilation." The system pulses fresh air in the offices

(30m³/h.person) and extracts air from thetoilettes and the elevator shaft.

" The fresh air input is situated on the roof." The system contains a heat-recovery unit.

Heat RecoveryHeat Recovery


3. Indoor Air Quality

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! In this project mechanical ventilation for indoor air quality was preferred to naturalventilation because of the following reasons:

" natural air intakes in the façade can imply acoustical problems as there is abusy highway at 100 m.

" mechanical ventilation allows to place the air input on the roof, where the airquality 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, airflows,...) was monitored during several weeks in four offices on the topfloor 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 externaltemperature 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 ofthe thermal mass

" Mechanical night ventilation could be controlled by temperature sensor to avoidtoo low indoor temperatures in the morning.

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Off.1

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Off.4

Ext.

Office without solarOffice without solarprotection...protection...

Monitoring results (2|)

summer monitoring

More aboutmonitoring:

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 withoutactive cooling. This concept seems to be compatible with the Belgianeconomic 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 asthere 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

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 ORrun the installation file ar32e301(1).exe in the directory\Installation

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The Keppekouter project - BREprojects.bre.co.uk/natvent/presentation/202_be2.pdf · The Keppekouter project Design issue Major findings ... indirect solar gains direct solar gains