View types and luminance effects on discomfort glare assessment from windows

The use of windows is the most common way of providing natural lighting to interior spaces of buildings. Natural lighting in buildings can displace the requirement for artificial lighting, and thus, has high potential to save energy. Discomfort glare from windows, however, is one of the fundamental barriers to the effective use of natural lighting in buildings. This study examined the potential effects of different window views on the subjective assessment of discomfort glare. Forty-eight subjects (24 men and 24 women) participated in the experiments. The experiment results indicated that the type of view and the distance of the view object are two critical factors of the subjective evaluation of discomfort glare. The results further showed that variations in the luminance distribution of a window (i.e., the ratio of the highest to the lowest luminance of the window) are not a statistically significant factor of subjective discomfort glare, but that there is a significant relationship between the mean luminance of a window and its subjective discomfort glare. This suggests that the mean luminance of a window, the type of window view, and the distance of the view objects should also be considered in the evaluation of the subjective discomfort glare from a window. This paper also discussed the energy-saving potential of daylighting strategies that consider discomfort glare from windows.