OCCUPANT BEHAVIOUR LIGHTING AND SMALL POWER
tenants (fi gure 1). The highest consuming tenant had an annual energy consumption of 155kWh/m2
, compared with 90kWh/m2
for the lowest consuming tenant. But how much of this energy use could be put down to the human factor?
Insights from behavioural psychology The industry’s current inability to accurately account for the impact of people on building energy performance is causing some to question the fundamental assumptions inherent within the design process, and instead to consider what we can learn from other disciplines. In particular, there has been much recent interest in using insights from behavioural psychology to develop a more sophisticated understanding of how people interact with their surrounding environments. The UK government has even adopted
this approach, establishing the Behavioural Insights Team in 2010 with the explicit purpose of applying techniques from behavioural psychology to policy. This has already been infl uential in the new design of the environmental performance certifi cate, as well as aspects of the Green Deal, such as incorporating the principle of ‘temporal discounting’ where people tend to prefer smaller incentives sooner rather than larger incentives later. Within buildings, developing our understanding of how people’s behaviour can affect energy consumption can have implications for a wide range of aspects, from the design and placement of controls to how energy information is fed back to the building occupants.
How the study worked The study was undertaken at an eight- storey multi-tenanted offi ce building located in central London, consisting mainly of open-plan spaces. To understand how much of the variation in electricity consumption between each tenant could be put down to behaviour, we had to compare metered electricity data with the results of an occupant survey. Each fl oor was approximately 2,000m2
and was divided into four separately metered zones, providing 32 individual areas that could be let to different tenants. In order to assess the impact of occupant behaviour on the building’s electricity consumption, each of the 32 metered zones was regarded as an individual data collection point. The electricity
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consumption for lighting and small power for each zone was collected and then correlated against behavioural scores for each zone, established, using a survey based on the theory of planned behaviour (TPB) – see box. The behavioural scores for each ‘predictor’ of TPB were obtained through a single-page questionnaire issued to each occupant. The scores were then averaged for each tenant-occupied zone in the building. The average score for each predictor was then compared to the metered electricity in the given zone.
200
NEW CIBSE TM54
TM54: Evaluating operational energy performance of buildings at the design stage encourages designers to consider the variability in lighting and small power specifi cation by individual tenants occupying the same building. This approach goes some way towards accounting for the variation in energy use by different occupants, prompting more representative estimates of energy use. See Mind the gap on page 34
150
100
50
Tenant A
Tenant B
Tenant C Figure 1: Annual electricity consumption for lighting and small power by tenants
Tenant D
September 2013 CIBSE Journal 41
Electricity Consumption (kWh/m2/
year)
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