Metrics to Predict Visual Discomfort in a Daylit Classroom

This paper reports on a pilot experiment to test the applicability of a group of metrics to the prediction of visual discomfort in a daylit classroom environment. In particular, if the position in relation to the window has an impact in the way visual discomfort from glare is reported, and if the metrics predict that discomfort accordingly. Subjects (N=21) performed a typical classroom task in four different positions in a classroom and were asked to rate visual discomfort from glare via a questionnaire at the same time that luminance measurements were collected. Daylight Glare Probability (DGP) provided the best agreement with the reported glare overall, but the ratio between the maximum luminance to mean task luminance of 30:1 in the 172º field-of-view depicted most of the reported discomfort votes. The results show that glare is reported for situations of low vertical eye illuminance, as also found in previous studies.