Impact of solar radiation on indoor thermal comfort near highly glazed façades in a hot-humid subtropical climate: An experimental evaluation

Abstract

Solar radiation has a profound impact on indoor thermal conditions, particularly in highly glazed spaces. However, there have been limited field measurements on this subject. Focusing on subtropical climate, this study investigated the effects of irradiation on thermal comfort from two aspects, disparities in glass properties and spatial positions, through a field measurement. Six test cells, each equipped with a representative type of glass, were established; two measurement points were set at inner and near-window positions to analyze the spatial disparities and impacts of solar radiation asymmetry. PMV-PPD-based evaluation criteria were employed to assess the long-term comfort levels and classified by environmental quality index (EQI); additionally, we assessed the risk of overheating by considering two indices: overheating hours and overheating severity, which represent the duration and extent of thermal discomfort. The results indicated that radiation asymmetry varied depending on glass properties and spatial/temporal difference, leading to partial thermal discomfort. Specifically, the MRT at the near-window point increased significantly, reaching 50.8 °C for single-pane glass, 40.1 °C for single-pane tinted glass, and a minimum of 32.8 °C for double-pane reflective glass after 14:30 due to direct sunlight. In contrast, the MRT at the indoor positions remained relatively stable at around 25 °C–27 °C, irrespective of the glazing type. SHGC of glass is critical for thermal comfort, as higher SHGC values intensify the sensation of extreme warmth. Through experiments, this study quantified the relationship between thermal discomfort and glazing properties, providing valuable insights for glazing facades design that can optimize indoor thermal environments.