Can the interaction between occupant behaviour and the indoor environment in residences be influenced?

In the context of global climate change it has been broadly recognized that energy use in buildings must be reduced. In many cases this has been achieved by decreasing the natural infiltration rate in buildings by means of a focus on airtightness. Increasing airtightness does decrease energy use, but it also increases the impact of occupant behaviour on energy use and indoor environment.

In Denmark the indoor environment is directly linked to energy use for heating. In most buildings the indoor environment is controlled by the occupant (via thermostat setting, window opening), so any change in the occupants’ control of the indoor environment will influence energy use. Both older and more recent studies of the influence of occupant behaviour on energy use report that an increased information level and feedback on energy use can be effective in influencing occupant behaviour.

The market penetration of smart meters has made it possible to measure and visualize energy use in real-time. Visualizing real-time consumption made it theoretically possible to provide feedback. Some authors were reluctant to recommend feedback from smart meters and a national roll-out of this approach, as national savings would then depend on the truth of an unproven assumption: that all occupants will act adaptively when provided with more information.

Their studies questioned the value of providing feedback to households not motivated to conserve energy and suggested that alternative approaches should be tested. The purpose of this Ph.D. project was to investigate whether feedback on the indoor environment could be used to adaptively influence occupants’ control of the indoor environment in such a way as to obtain healthy and comfortable homes and reduced energy use for heating.

The project consisted of a literature study and four field studies that focused on how to affect occupants’ control of the indoor environment. The four studies used measurements of the temperature, relative humidity, and CO2 concentration in 84 rental apartments. The conclusions made in the thesis are derived from an analysis of the measurements performed in the apartments.

The apartments were in three multi-storey buildings in three different municipalities of the Copenhagen area of Denmark. The influence of how total heat cost was allocated between tenants was studied in two buildings and a significant influence on the control of indoor environment was  demonstrated.

The measurements indicated that heat cost allocation was a driver for occupants’ behaviour. The measurements further showed the energy-saving potential of shifting from master-metering to submetering. Two different feedback procedures were used to test the effect of providing indoor environmental feedback.

The first method combined real-time feedback with monthly feedback letters. The second method combined real-time feedback with weekly feedback letters. The effects of the feedback procedures were investigated by using measurements, interviews and questionnaires. Feedback on energy use gave occupants a monetary incentive and an environmental incentive to conserve energy.

By using indoor environmental feedback it was possible to use health, comfort, monetary and environmental incentives to promote energy conservation. The studies highlighted the importance of occupants being motivated to adapt their control of the indoor environment by acting on feedback. The results further indicated that occupants without a monetary incentive were not as interested in using the feedback as occupants with a monetary incentive.

The difference between the feedback procedures supported the findings of earlier studies, that feedback should be disseminated as frequently as possible. The studies demonstrated the importance of barrier-free access to real-time feedback, as even a little barrier caused the occupants to ignore the feedback.

It is recommended that feedback should be disseminated by using a mobile platform, as a dedicated application, and not just through a website.