Residential electric lighting use during daytime: A field study in Swedish multi-dwelling buildings

Abstract

This paper evaluates the effect of room function and orientation on daytime electric lighting use in dwellings, and the confounding role of room design aspects. A questionnaire survey was conducted in six multi-dwelling buildings including 75 apartments located in Malmö, Sweden (Latitude: 55.6 °N). Occupants were asked how often they use electric lighting during daylight hours, in three rooms of different functions, namely the kitchen, the living room and the bedroom. In a preliminary step, the behavior of occupants regarding electric lighting use was evaluated, to test whether design and orientation can affect switch-on behavior or whether it is random and unpredictable. In the next step, statistical analysis was performed to verify whether there is a relation between daytime electric lighting and room function, room orientation or both. Results indicate that electric lighting use did not vary significantly among occupants living in rooms of similar geometry, especially when living in West-oriented rooms. With respect to room function, overall it was shown that daytime electric lighting use was more frequent in kitchens. However, the study showed that electric lighting use in kitchens is associated with specific design features and not with room function per se. With respect to orientation, a consistent finding was that West-facing rooms use electric lighting less frequently compared to rooms of other orientations, and significantly less frequently compared to East-facing rooms, which can be explained by diurnal occupancy patterns characterizing residential spaces. The implications of the findings on daylight design criteria for residences are discussed.