Do lighting control and user interface design matter to occupant behaviour? The case of optimal lighting use in non-residential buildings

Abstract: The lowering of energy use from artificial lighting in buildings is vital to reaching the goal of reducing CO2 emissions. Hence, changes in individuals’ behaviours regarding lighting use have received increased attention. Feedback on energy use has often been used to change individuals’ behaviour. However, it is not clear to what extent this approach can be applied for non-residential buildings, where individuals’ use of lighting may differ from that at home. In this type of building, other types of interventions may be required. This thesis addresses the possible significance of (i) lighting control and (ii) user interface designs for effective use of lighting, referred to as ‘optimal lighting use’, of occupants in non-residential buildings. The main objective was to explore individuals’ responses to different designs of controls and interfaces, and thereby the effects on lighting energy use. Individuals’ use of electric lighting with six different controls was investigated through field measurements in 18 single-occupant offices. A self-report diary and electronic measurement using a data logger were used to collect the data during a one-year period. The self-reported data were found to correlate with the logged data, suggesting that the diary was a suitable tool for measuring lighting use with different lighting controls. Generally, the results based on the logged data showed that use of electric lighting varied among the individuals using the different controls and indicated the potential of combining manual/automatic dimming controls with manual on/off or occupancy switch-off controls to achieve optimal lighting use. Further, different designs of everyday interfaces for lighting controls (i.e. light switches) were investigated. In controlled environments, laypersons’ perceptions of ten different lighting switches with regard to particular characteristics were assessed by questionnaires and found to be different among the switches. Field observations were subsequently conducted for 30 days for each of the original and alternative switches using a data logger in a public toilet in a hospital. The switches’ characteristics (oversize, simplicity as well as affordances) were found to affect whether individuals used lighting optimally. Also, occupants’ use of lighting with different light switches in a dining room and a dayroom, regarded as shared environments, located in patient wards, were investigated. The self-reported questionnaire showed that satisfaction with lighting, affective-related beliefs and general lighting-use behaviours were important in influencing optimal lighting use by individuals. Further, measurements from data loggers revealed that the different designs of the switches had a significant influence on lighting and energy use. This thesis contributes by providing information on different methods for investigating optimal lighting use and its relevant factors. The findings should facilitate the design of interventions to reduce energy use from lighting. In addition, the user perceptions employed to define the interfaces’ characteristics could contribute to the development of guidelines for designing user interfaces for lighting controls with respect to users’ viewpoints.