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BRE Energy Efficient Office
of the Future
The Energy
Efficient Office
Presentation
of the building
Design Issue
Building
concept
Monitoring
Winter
Summer
Conclusions
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Building presentation (1...)
The Energy
Efficient Office

The building was designed by Architects Fielden Clegg Design.
Presentation
of the building

The building has three storeys in two blocks connected by an atrium at
the west wall of the building. The main axis is running east-west.
The ground and first floor contain open plan and cellular offices. The
second floor is a large open plan office.
Design Issue
Building
concept

Monitoring
Winter

Summer
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On the ground floor there is a large lecture theatre to the north. This is
connected to the main building by a circulating zone containing toilets
and a display area.
Building presentation (2|)
The Energy
Efficient Office
N
Plan view of
ground floor
Lecture
theatre
Presentation
of the building
Building
concept
Monitoring
Winter
Circulation
zone
Design Issue
Main
building
Summer
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Atrium
The Design Issue
The Energy
Efficient Office

Presentation
of the building
Design Issue
Building
concept
The design brief called for ‘outstanding energy performance’. The
Performance Specification, a key element of the building brief, dictates
performance targets for energy consumption and carbon dioxide (CO2 )
emissions. The targets (47 kWh/m² for gas - 36 kWh/m² for electricity - 34
kg/m² CO2 emission) represent a 30% improvement on current best practice
and were to be met by:


Monitoring
Winter

Summer

avoiding or minimising the use of air-conditioning
maximising the benefits of the building fabric in terms of reducing the heating and
cooling loads
minimising the use of artificial lighting while actively exploiting daylight
applying the appropriate level of automatic and user control
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
However, energy efficiency is only acceptable within the parameters of a
comfortable and healthy working environment. The internal design conditions
for thermal comfort were:
 For winter: 18°C minimum internal temperature
 For summer:
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– 25°C is not to be exceeded for more than 5% and
– 28°C is not to be exceeded for more than 1% of the year
The building concept (1...)
natural ventilation
The Energy
Efficient Office

Natural ventilation has been utilised to minimise the use of fans.
The ground and 1st floors are stack driven using solar towers on the
southern façade. The 2nd floor has cross ventilation via openable windows.
(see next slides..)
Voids in the ceiling slab act as ducts bringing air in from outside and
exhausting air out to ventilation stacks.

Natural ventilation is used to:
 Improve the thermal comfort:
Intensive (night) ventilation can be
applied to cool down the thermal mass
(exposed ceilings) of the building.
 Control the IAQ:
The occupants can open windows to
control the IAQ
Presentation
of the building
Design Issue
Building
concept
Monitoring
Winter
Summer
Conclusions
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exposed ceilings
The building concept (2...)
ventilation strategy
The Energy
Efficient Office
Presentation
of the building
Stack ventilation on hot
still summer’s day
Design Issue
Building
concept
Monitoring
Winter
Summer
Conclusions
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Voids in the
ceiling slab
The building concept (3...)
ventilation strategy
The Energy
Efficient Office
Presentation
of the building
Cross ventilation on
windy summer’s day
Design Issue
Building
concept
Monitoring
Winter
Summer
Conclusions
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Many ventilation
openings are
automatically
controlled. However
can override the
automatic settings
for windows
The building concept (4|)
shading and lighting
The Energy
Efficient Office

Solar gains are reduced by
moveable external louvres on the
South side of the building. These
louvres improve the thermal summer
comfort, but also control glare while
still allowing daylight.

A fully integrated, intelligent and
efficient lighting system has been
installed which automatically
compensates for daylight levels and
occupancy, controlling each light
separately. In this way the internal
gains of lighting are minimised and
linked to the available daylight.
Reducing the internal gains of
lighting is an important step toward
summer comfort in office buildings.
Presentation
of the building
Design Issue
Building
concept
Monitoring
Winter
Summer
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External
louvres
Lighting:
control sensor
Monitoring the building
The Energy
Efficient Office
Presentation
of the building


Design Issue
Building
concept
Monitoring
Winter
Summer

Conclusions
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The building was
monitored in summer
and winter.
Two rooms on the
1st floor were
monitored. The
rooms were used
normally by
occupant.
Night cooling was
utilised during the
summer months.


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Room 2
Corridor zone
Atrium
Open plan
Ventilation stacks
The following parameters were measured:

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Room 1

Internal and external CO2 concentration as an indicator of IAQ.
Fresh air flow rates and local wind speed and direction.
External air and internal air and globe temperatures.
N
Winter monitoring (1...)
air change rates
The Energy
Efficient Office

Presentation
of the building



Design Issue
Building
concept
Air change rates are similar in both rooms.
Higher ventilation rates coincide with periods of occupancy.
There is some correlation of air change rate with wind speed and direction.
Air change rates were adequate in both rooms: the CO2 -concentrations are not too
high (see next slide) and the air supply is almost zero outside the office hours
(reduction of ventilation losses).
Winter, air change rate in the monitored rooms.
Monitoring
10
9
Winter
Summer
Conclusions
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Air change rate (1/h)
8
Room 2 ach
Room 1 ach
7
6
5
4
3
2
1
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0
15:00
1/8/98
19:00
1/12/98
23:00
16/01/1998
3:00
21/01/1998
Date/Time
7:00
25/01/1998
11:00
29/01/1998
Winter monitoring (2...)
CO2-concentrations
The Energy
Efficient Office

Presentation
of the building

CO2 concentrations are generally below the limit of 1200 ppm.  The IAQ
is acceptable
Increased levels of CO2 coincide with occupancy.
Design Issue
Winter, carbon dioxide concentration in the monitored rooms.
Building
concept
1600
Monitoring
1400
Summer
Conclusions
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Room 2 CO2
Carbon dioxide (ppm)
Winter
External CO2
Room 1 CO2
1200
1000
800
600
400
200
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0
15:00
1/8/98
19:00
1/12/98
23:00
16/01/1998
3:00
21/01/1998
Date/Time
7:00
25/01/1998
11:00
29/01/1998
Winter monitoring (3|)
temperatures
The Energy
Efficient Office

Presentation
of the building

Temperatures were between 2 to 5oC above the design minimum
temperature (18°C).
There was little difference between air and globe temperatures.
Design Issue
air and globe temperatures in the monitored rooms.
Building
concept
25
Monitoring
Summer
Conclusions
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Temperature (degC)
Winter
20
Room 1 globe temp
15
Room 2 globe temp
External temp
10
5
0
15:38:26
14/01/98
23:38:26
17/01/98
7:38:26
21/01/98
-5
Date/Time
16:29:28
24/01/98
0:29:28
28/01/98
Summer monitoring (1...)
air change rates
The Energy
Efficient Office

Presentation
of the building

Design Issue
Building
concept


Air change rates in room 1 were higher than those in room 2, possibly due to
poor mixing as a result of opening windows.
Again higher ventilation rates coincide with occupancy.
Air change rates were adequate during occupied periods.
Both offices were closed and locked at night and so did not benefit from night
ventilation.
Monitoring
air change rates in the monitored offices.
Winter
30
Room 1
25
Conclusions
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Air Change Rate (1/h)
Summer
Room 2
20
15
10
5
0
31/7/97 15:24
2/8/97 17:19
6/8/97 13:53
8/8/97 15:57
-5
-10
Date/Time
10/8/97 17:52
13/8/97 10:22
15/8/97 12:26
Summer monitoring (2...)
CO2-concentrations
The Energy
Efficient Office

CO2 concentrations were generally below 1000 ppm. The IAQ is acceptable
Presentation
of the building
carbon dioxide concentrations in monitored rooms.
Design Issue
Monitoring
Winter
Summer
Conclusions
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Carbon dioxide concentration (ppm)
Building
concept
900
External
Room 1
Room 2
600
300
0
31/7/97 15:21
2/8/97 17:16
6/8/97 13:50
8/8/97 15:54
Date/Time
10/8/97 17:49
13/8/97 10:19
15/8/97 12:23
Summer monitoring (3|)
temperatures
The Energy
Efficient Office
Presentation
of the building


The 28°C design maximum temperature was not exceeded.
The 25°C lower design temperature was exceeded on some occasions.
air temperatures in the monitored rooms.
Design Issue
30
Building
concept
Winter
Summer
Conclusions
More
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26
Air Temperature (degC)
Monitoring
28
External air temps
Room 1 air temps
Room 2 air temps
24
22
20
18
16
14
12
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10
31/7/97 16
2/8/97 08
4/8/97 00
7/8/97 10
9/8/97 02
Date/Time
10/8/97 18
12/8/97 10
14/8/97 17
Conclusions (1...)
The Energy
Efficient Office

Winter Indoor Climate:
 Adequate ventilation is provided.
 Internal air quality is acceptable.
 Comfortable internal temperatures are achieved.

Summer Indoor Climate
 Adequate ventilation is provided.
 Comfortable temperatures are maintained though the lower design
temperature was sometimes exceeded during warm spells.

The building has external louvres to reduce the solar gains. Moreover, the
building makes use of night cooling. Cooler night time air is drawn in via the
openable windows and ceiling voids. Fans in the ventilation towers can be
used to assist purging. Ground water cooling can also be used.
Presentation
of the building
Design Issue
Building
concept
Monitoring
Winter
Summer
Conclusions
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Conclusions (2|)
The Energy
Efficient Office

Presentation
of the building
Design Issue
The good solar control and combination of high thermal mass and night
ventilation did result in lower temperatures and helped maintain comfort.
By using ground water cooling the lower design temperature (25°C) could
be met.
Building
concept
33
Monitoring
31
one weeks external and internal air temperatures during August 1997.
External
Winter
Conclusions
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29
Air Temperature degC
Summer
Office
27
25
23
21
19
17
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15
06/08
07/08
08/08
09/08
10/08
Date/Time
11/08
12/08
13/08
More information...
The Energy
Efficient Office
Presentation
of the building
Design Issue
Building
concept
Find more information on the PROBE building in the following documents:
\Reports \Monitoring Reports \Summary Reports\gb1summ.pdf
 global presentation of the buildings (4p./building)
 contents: building description - ventilation strategy and technology winter and summer monitoring results - conclusions
Monitoring
Winter
Summer
Conclusions
\Reports \Monitoring Reports \Detailed Reports\gb1det.pdf
 detailed reports of all 19 monitoring campaigns (20p./campaign)
 contents: monitoring set up - analysis of results - conclusions
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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