BUILDING CASE STUDY POST-OCCUPANCY EVALUATION
250
Electricity – Total regulated + non-regulated
200 Electricity – non-regulated 150 Electricity – regulated – non-cooling 100 Electricity – regulated – cooling 50 Gas for space heating and hot water 0 Actual consumption
Good practice benchmark
Typical benchmark Figure 4: Comparison of actual energy use with industry benchmarks
consumption (<5%). This is remarkable given the high levels of user satisfaction with summer comfort, and demonstrates that natural ventilation can work well in office buildings with suitable environments. At the Digital Lab this is allowed by a combination of passive design to reduce summer solar gains, narrow plan with central atrium (22m plan depth and 6m atrium), location of offices of higher occupancy density along the northern elevation, and reasonable occupancy levels. Electricity consumption related to process
PROJECT TEAM Client: University of Warwick
Architects: Edward Cullinan Architects
MEP consulting engineers: Hoare Lea Structural engineer: Arup BREEAM assessor: Hoare Lea Quantity surveyors: Jacobs
Main contractor: Norwest Holst Construction Ltd
Project manager: University Estates Office
loads (that is, significant IT equipment for research purposes, lifts and small power uses) represents the majority (~60%) of the electrical consumption. In future building, the university will look at analysing this in more detail, for example, with sub-metering of lighting and small power, rather than by areas, such as floor-by-floor distribution boards, as this would help assess the impact of users equipment or quantify the energy savings allowed by fine-tuning the controls strategy. For example, incidental observations indicate that a certain level of manual control over lighting could create opportunities to reduce electricity consumption where lighting is currently controlled by occupancy sensors.
Earth labyrinth Temperature sensors were installed at two inlets and two outlets of the earth labyrinth to assess its performance, and temperatures were recorded for a year. This allowed the following observations: l In winter, the temperature at the outlet of the labyrinth mostly varied between 12 and 17C;
28 CIBSE Journal April 2012
l In summer, the temperature at the outlet of the labyrinth mostly varied between 14 and 20C.
This analysis therefore indicates that the labyrinth has an important stabilising effect on the supply air, pre-heating it in winter and pre-cooling it in summer and therefore reducing energy consumption for space heating and mechanical cooling. The university is likely to conduct more detailed monitoring in the future, since this is potentially seen as a useful feature in low carbon office buildings.
Realising the design intent The innovative nature of the building explains the learning curve experienced in the early stages of occupation. The university has shown a keen interest in using lessons from this study to influence their future procurement process, with more emphasis on the final stages before occupation and possibly the adoption of Soft Landings principles (see
www.softlandings.org.uk). One factor that should help the university
to implement careful handover procedures is the use of BREEAM: the BRE now require a post-construction review before certifying a building, which means that construction teams need to provide evidence that the commitments made at design stage, such as following best practice commissioning procedures or issuing a simple building user guide, have been implemented.
Conclusions The post-occupancy evaluation of the Digital Lab has highlighted a number of lessons that should be valuable for the university’s future buildings and for designers of buildings with low carbon aspirations. The design has proved highly satisfactory in creating a pleasant environment, achieved at good energy consumption levels. Interestingly, the success of the building’s architectural and environmental strategy already offers an example of a feedback loop, as Edward Cullinan Architects and Hoare Lea have put forward a similar concept in their proposals for the Institute for Sustainability, in the London Thames Gateway. Furthermore, revisiting the building
has contributed to raising awareness and identifying key areas of focus for a long-term management programme by the university, rather than being seen as an end in itself. CJ
l JULIE GODEFROY is an executive sustainability consultant, and ASHLEY BATESON a partner at Hoare Lea
www.hoarelea.com
www.cibsejournal.com
kWh/sq mgross)/yr
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