1. BRE Energy Efficient Office of the Future
The Energy Efficient Office
Presentation of the building
Design Issue
Building concept
Monitoring
Winter
Summer
Conclusions
More information...
Back to “Select a building”
NatVent

2. Building presentation (1...)
The building was designed by Architects Fielden Clegg Design.
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.
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.

3. Building presentation (2|)
Plan view of ground floor
Lecture theatre
Main building
Circulation
zone
Atrium

4. The Design Issue
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:
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
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:
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

5. The building concept (1...) natural ventilation
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
exposed ceilings

6. The building concept (2...) ventilation strategy
Voids in the ceiling slab
Stack ventilation on hot still summer’s day

7. The building concept (3...) ventilation strategy
Cross ventilation on windy summer’s day
Many ventilation openings are automatically controlled. However can override the automatic settings for windows

8. The building concept (4|) shading and lighting
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.
External louvres
Lighting: control sensor

9. Monitoring the building
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.
Room 1
Room 2
Open plan
Ventilation stacks
Corridor zone
Atrium N
The following parameters were measured:
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.

10. Winter monitoring (1...) air change rates
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).

11. Winter monitoring (2...) CO2-concentrations
CO2 concentrations are generally below the limit of 1200 ppm.  The IAQ is acceptable
Increased levels of CO2 coincide with occupancy.
Winter, carbon dioxide concentration in the monitored rooms.
1600
External CO2
1400
Room 2 CO2
1200
Room 1 CO2
1000
Carbon dioxide (ppm)
800
600
400
200
15:00
19:00
23:00
3:00
7:00
11:00
1/8/98
1/12/98
16/01/1998
21/01/1998
25/01/1998
29/01/1998
Date/Time

12. Winter monitoring (3|) temperatures
Temperatures were between 2 to 5oC above the design minimum temperature (18°C).
There was little difference between air and globe temperatures.

13. Summer monitoring (1...) air change rates
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.

14. Summer monitoring (2...) CO2-concentrations
CO2 concentrations were generally below 1000 ppm. The IAQ is acceptable

15. Summer monitoring (3|) temperatures
The 28°C design maximum temperature was not exceeded.
The 25°C lower design temperature was exceeded on some occasions.

16. Conclusions (1...) Winter Indoor Climate:
Adequate ventilation is provided.
Internal air quality is acceptable.
Comfortable internal temperatures are achieved.
Summer Indoor Climate
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.

17. Conclusions (2|)
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.

18. More information... NatVent
The Energy Efficient Office
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
\Reports \Monitoring Reports \Detailed Reports\gb1det.pdf
detailed reports of all 19 monitoring campaigns (20p./campaign)
contents: monitoring set up - analysis of results - conclusions
Presentation of the building
Design Issue
Building concept
Monitoring
Winter
Summer
Conclusions
More information...
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: OR run the installation file ar32e301(1).exe in the directory \Installation
Back to “Select a building”
NatVent