Testing the predictive power of visual discomfort from glare metrics in the near-window and near-wall zones of the daylit classroom environment

The objective of the present study was to find how well a group of selected luminance-based metrics predict reported visual discomfort from daylight glare in spatial conditions that differ from the conditions where metrics tend to developed and validated for. An empirical study involving the assessment of visual discomfort from glare by n=50 subjects (n=185 cases) in a daylit-only classroom space was carried out to investigate this problem. It was found that the glare indexes were the most robust metrics predicting reported glare. However, as all metrics failed most of the statistical tests in the near-wall zone of the classroom, it can be said that none of the metrics was able to predict with enough accuracy the glare reported across the space. Indeed, the metrics show a very poor performance in the sitting positions away from the window, an aspect that requires further investigation.