OCCUPANT BEHAVIOUR LIGHTING AND SMALL POWER
The findings from this study suggest that THEORY OF PLANNED BEHAVIOUR
Developed in the Nineties, the Theory of Planned Behaviour (TPB) is one of the most widely applied behavioural models. In essence, it claims that, in order to predict whether a person intends to do something, it is necessary to know the following three factors:
■‘Behavioural attitude’ – whether the person is in favour of doing it
■‘Subjective norm’ – how much the person feels the social pressure to do it
■‘Perceived behavioural control’ – whether the person feels in control of the action
By adjusting these three ‘predictors’, the likelihood that the person will carry out a specific action can be increased or decreased as required – a concept that is illustrated above.
Behavioural atitude
Subjective norm
Perceived behavioural control
Figure 2: The theory of planned behaviour1
A 2010 study by the University of Bristol and Buro Happold used TPB to quantify the impact of occupant behaviour on residential buildings and discovered that, even when factors such as number of occupants and floor area were accounted for, gas and electricity consumption varied by a factor greater than three.
A need for control The results demonstrated that only one predictor from TPB was having a significant impact on electricity consumption: perceived behavioural control, or whether the person felt in control of the action in
question. Analysis revealed that about 17% of the variation in monthly electricity consumption for lighting and small power between building zones could be accounted for by the amount of control that the occupants believed they had. In the building investigated, this implies that lower energy consumption can be expected where occupants perceive themselves to have a high level of control over lighting and appliances. The other predictors – behavioural attitude and subjective norm – were not found to have a significant effect on zonal electricity consumption.
BEHAVIOURAL ATTITUDE
18 16 14 12 10 8 6 4 2 0
0 5 10 15 20 25 Median Score Figure 3: Scatter plots of electricity consumption vs TPB median scores 42 CIBSE Journal September 2013
www.cibsejournal.com 30 35 40 45 -5 0 5 10 15 Median Score 20 25 30 0 5 10 15 Median Score 20 25 SUBJECTIVE FORM Intention Behaviour
the more control people perceive that they have over their surroundings, the less energy they consume. This premise goes against the current design trend for more automation in buildings. This highlights the importance of considering how the building users will be able to control their environmental conditions during the entire design process, and suggests a clear benefit in implementing usable and well-located controls, rather than technologies such as passive infra-red detection and other automated services. As controls are often only considered relatively late in the design process, they are highly susceptible to value engineering. Efforts should be made to ensure that intuitive and well-positioned controls are taken into account throughout the design process. Traditional attempts to reduce the influence of occupants on energy consumption in existing buildings revolve around the assumption that people’s behaviour can be altered by providing them with information about their undesirable actions. However, there is evidence to suggest that while this approach may serve to influence attitudes, it often has a negligible effect on actual behaviour. Insights from behavioural psychology can help us to develop a more sophisticated understanding about how we can engage building users and encourage energy-efficient behaviour. CJ
REFERENCE
1 The Theory of Planned Behaviour. Organizational Behavior and Human Decision Process, vol. 50, pp. 179-211
ANNA MENEZES and RICHARD TETLOW are research engineers at AECOM and steering group members of the CIBSE Young Energy Performance Group
PERCEIVED BEHAVIOURAL CONTROL
Monthly Electricity Consumption (kWh/m2
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