Thermal Comfort Evaluation for the Rural Elderly Based on the Spatiotemporal Differentiation of Daily Activities During Summer in Xi’an, China

To meet the comfort and health needs of the elderly in daily activity environments, a refined temporal and zonal thermal environment design across diverse spaces must align with dynamic changes in their daily activity spatiotemporal trajectories. This constitutes a research gap in the existing literature. This study focused on elderly individuals in rural Xi’an, integrating on-site subjective daily activity questionnaires, thermal comfort field surveys, and continuous thermal environment monitoring to evaluate summer thermal environments based on spatiotemporal activity differentiation. The key conclusions are as follows: (1) Elderly people primarily engage in activities in indoor and outdoor spaces, with considerably fewer activities occurring in semi-outdoor areas. Summer outdoor activities occur between 6:00 and 9:00 and 17:00–21:00, while indoor activities dominate other times. (2) The established adaptive thermal response models indicate indoor and outdoor neutral temperatures are 23.8 °C (Operative temperature) and 28.8 °C (UTCI). Indoor 80% acceptability upper limit is 27.5 °C and outdoor 80% acceptability upper limit is 34.1 °C. These results exhibit distinct differences from those observed in alternative climate zones and urban areas in the same climate zone. (3) The thermal environment of outdoor shaded areas remains within the acceptable range for a longer duration than that of indoors, and kitchens have the worst indoor thermal quality. This evaluation provides supplementary insights into current spatiotemporal thermal environment research.