Daylighting performance and discomfort glare assessment of granular aerogel glazing system: A full-scale comparative experiment

Abstract

Energy saving, natural lighting, and visual comfort are essential factors to be considered in window design. Granular aerogel glazing system (AGS) has great energy-saving potential, whereas the studies on daylighting performance, especially the visual comfort of AGS are very limited. In this study, a full-scale experiment was conducted to evaluate the daylighting performance and discomfort glare of AGS compared to that of the double-glazed system (DGS) in overcast and sunny days. The horizontal illuminance in the front, middle, and back positions, the vertical illuminance, and the illuminance uniformity were comprehensively analyzed. The high dynamic range (HDR) photograph technique was used and validated. The daylight glare probability (DGP) and daylight glare index (DGI) identified by the task area method, threshold method, and factor method were extracted from HDR images by Evalglare. The results showed that the average horizontal illuminance in the AGS test room is lower than that in the DGS test room. However, due to the scattering effect of AGS, the horizontal illuminance of the AGS test room may be higher than that of the DGS test room in positions where no direct sunlight directly hitting at noon in sunny days. The maximum increasing rate of the hourly horizontal illuminance in the middle and back positions of the AGS test room in September is 37.8% and 54.5%. It is also found that glare may occur in the AGS test room mainly due to excessive luminance. The discomfort glare in the AGS test room may be intolerable in sunny days.