Quantifying the effects of indoor non-uniform solar radiation on human thermal comfort and work performance in warm season

Window-through solar radiation significantly affects indoor thermal environments as well as human thermal comfort and health. This study aims to investigate occupants' thermal comfort and work performance with indoor solar radiation conditions in warm season. 24 subjects participated in six field tests with varying solar radiation conditions, while recording environmental, physiological, and psychological parameters. Results indicate that strong solar radiation significantly impacts physiological, psychological responses, and work performance. Specifically, compared to no direct solar radiation condition (only weak diffuse radiation), mean skin temperature increased by 0.6–1.6 °C, while local skin temperature increased by up to 2.7 °C. Additionally, SpO2 decreased and PR increased with higher solar radiation intensity. Besides, averagely, at the same operative temperature (Top) (28 °C), the percentage of thermal discomfort was approximately 18 % higher with direct solar radiation compared to without. The upper limit of the optimal Top range (less than 20 % of the subjects felt thermal discomfort and unproductive) with direct solar radiation (25.1 °C) is about 3 °C lower than without direct solar radiation (28.0 °C). For high willingness to work (90 %), the upper limits of the optimal Top range with and without exposure to direct solar radiation are 24.2 °C and 26.8 °C, respectively.