Effects of metabolic rate on the human thermal responses: A large cross-sectional field survey

The impacts of metabolic rate (activity level) on human thermal response have not been adequately addressed. Extensive data from the Chinese Thermal Comfort Database were utilized to classify subjects based on their activity levels, including resting, sitting, standing, and walking. Variations in thermal responses among people with different activities in real-life scenarios were analyzed. The thermal neutral temperatures and acceptable comfort ranges for these groups were established. Furthermore, the impact of activity on thermal responses for males and females was investigated. Results indicate that as the metabolic rate increases, subjects’ thermal sensation vote gradually increases, while the comfort level decreases. The human thermal neutral temperatures with different activities were found to be 22.1 °C, 20.2 °C, 20.1 °C, and 18.9 °C, respectively. It was observed that males exhibit lower thermal neutral temperatures than females, with this gap narrowing as metabolic rate rise. Notably, for every 0.1 met increase in metabolic rate, the thermal neutral temperature decreases by approximately 0.3 °C. The acceptable temperature ranges for the four activity states were 15.7–31.0 °C, 13.9–29.7 °C, 16.0–27.0 °C, and 15.6–28.3 °C, respectively. As metabolic rate increase, the range narrows for subjects. The findings enhance the understanding of human thermal adaptation mechanisms, provide data support for personalized thermal comfort, and hold promise for reducing energy consumption in buildings.