Prediction of discomfort glare from windows

Abstract

Visual discomfort in a day-lit interior environment is usually represented by the degree of discomfort glare perceived by the user. The paper reports on the evaluation of several models for the prediction of discomfort glare from daylighting, using data collected over a 10-month period, in a purpose built test cell. The Daylight Glare Index (DGI) was evaluated according to different interpretations of the background luminance (L_b). The evaluation of the models led to a better understanding of the effect of the adaptation function and a modified DGI is explored in light of these findings. The Unified Glare Rating (UGR), which is the CIE model for the prediction of discomfort glare from artificial lighting, was also evaluated to identify the differences between the two approaches and to test the potential for the development of a general UGR that would include both lighting environments.