Understanding local thermal comfort and physiological responses in older people under uniform thermal environments

The ageing population has increased the attention on care services for older people, particularly concerning their health and thermal comfort. However, most existing studies focus on the overall thermal comfort of older people, with insufficient research into their local thermal needs for different body parts, impeding precise thermal adjustments and optimal thermal satisfaction. This study investigated the local thermal comfort and skin temperature of older people under various environmental conditions. The results reveal significant variations in local thermal perceptions across body parts in older people under non-neutral thermal conditions. When wearing standard clothing (long-sleeved shirt and trousers) in cool environments, the back was the coldest part, followed by the lower body. In warm environments, the back, head, and chest exhibited higher thermal sensations. Weighting factors quantifying the influence of local thermal sensations on overall thermal sensation were calculated, identifying the head and back as key regions in warm conditions, and the back, arms, and legs in cool conditions. Local skin temperature also varied significantly across the body, with the head and trunk exhibiting higher temperatures and showing less fluctuation in response to environmental changes compared to the limbs. Furthermore, regression models between local thermal sensation and skin temperature were developed. Compared to the results from young people, older subjects showed significantly smaller variations in local thermal sensations across the body, along with significantly differences in local skin temperatures. These findings highlight the importance of considering the local thermal needs and preferences in older people when designing age-friendly indoor thermal environments.