Predicting Visual Comfort Conditions in a Large Daylit Space Based on Long-term Occupant Evaluations: a Field Study

We present a method for predicting visual comfort conditions of occupants in daylit spaces. Using an online survey, 67 occupants of a multi-story open plan studio space evaluated long-term visual comfort at their workstations in a substantially daylit space which is known to have glare problems. Visual comfort simulations of each occupant’s specific location were conducted and compared to the survey results. Simulations included discomfort glare, monitor contrast, visibility of the sun in the field of view and the presence of direct light on the workplane. It was found that combining all four modes of discomfort analysis allows close agreement with occupant assessments ranging from 69% of morning assessments up to 87% of afternoon assessments. In contrast, following current practice by only considering a single source of discomfort, leads to under-predicting the glare problem. Only 29 to 47 percent of significant visual comfort assessments in this study were caused by a solitary type of discomfort. These findings show that visual discomfort is often caused by multiple independent effects, which must be evaluated simultaneously for a reliable visual comfort analysis.