Towards Subjectivity in Annual Climate-Based Daylight Metrics

This paper presents a post-occupancy study of 543 participants in 10 daylit office buildings in Singapore. Calibrated daylighting and electric lighting simulation models of each building were created and verified. HDR photographs and vertical and horizontal illuminance measurements were taken at each participant’s workspace, and a survey on their long-term and instantaneous subjective evaluations of lighting were collected. For the first time, this study compares climate-based daylighting metrics (CBDM’s) to occupant’s longterm subjective impressions. The authors find that simulated mean annual horizontal illuminance correlates strongly with occupants’ satisfaction with access to daylight. 50% occupant satisfaction with daylight begins at levels as low as 80 lx, far below current lighting sufficiency standards. Vertical illuminance measures did not exhibit strong correlations with reported discomfort. These results are an initial investigation of CBDM’s use for more than lighting sufficiency and illustrate the need for further study of overlighting metrics.