Physiological equivalent temperature-based and universal thermal climate index-based adaptive-rational outdoor thermal comfort models

Outdoor thermal comfort models are predominant in guiding urban design and outdoor space usage. Both the heat balance of the human body and thermal adaptations significantly affect outdoor thermal comfort. This study proposes adaptive-rational outdoor thermal comfort models to account for the heat balance and thermal adaptations simultaneously. Two widely used rational thermal indices of outdoor thermal comfort, i.e., Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI), are implemented to account for the heat balance. The adaptive and extension methods are implemented based on the rational thermal indices to develop the adaptive-rational outdoor thermal comfort models. The validation results show that compared with the PET-based rational model, the PET-based adaptive-rational models with adaptive and extension methods improve the accuracy and robustness by up to 83% and 86% respectively. Compared with the UTCI-based rational model, the UTCI-based adaptive-rational models with adaptive and extension methods improve the accuracy and robustness by up to 87% and 87% respectively. The proposed adaptive-rational outdoor thermal comfort models contribute to developing livable urban environments.