Investigating the Relationship Between Subjective Assessments and Spatial Daylight Autonomy in Offices

Available daylight provision metrics are based on climatic data to assess temporal and spatial daylight availability indoors. The current targets used to benchmark a room‘s daylight performance are related to the visual perception of office workers. This study aimed to examine the relationship of illuminance and spatial Daylight Autonomy (sDA) with occupant‘s satisfaction using different methods to collect their subjective perception. We collected data on thermal and luminous environments, such as vertical and horizontal illuminance through a field study at the Technical University of Denmark (DTU) during the spring of 2024. Nine volunteers answered questionnaires to assess their preference and satisfaction with the amount of daylight on the desk, and their satisfaction with the perceived daylit area in the room. The measurements were conducted on separate days, under two different conditions: (1) blind/curtains open; (2) blinds/curtains as the participants typically use and prefer. Under both scenarios, the electric light was always off. The results indicated that occupant satisfaction correlated significantly with illuminance levels and perceived daylit areas under non-glaring conditions, with horizontal illuminance below 1510 lux and vertical illuminance below 1650 lux. However, in the presence of glare, satisfaction showed a stronger correlation with the proportion of the daylit area rather than illuminance. If integrated with other studies with a similar approach, the results can be used to optimize daylighting in indoor environments for well-being by providing insights for more occupant-centric standards in daylighting.