Indoor thermal comfort and ageing: A systematic review

Understanding the differences in thermal comfort between older and younger people is crucial for designing appropriate indoor environments for ageing populations. Although many studies have compared the thermal comfort between the two age groups, consistent conclusions are still lacking due to variations in the environmental conditions studied. This study presents a comprehensive literature review to systematically analyze the impact of ageing on indoor thermal comfort under different environmental conditions. The results suggest that age-related differences in thermal comfort are dependent on environmental conditions. In climate chamber experiments with same clothing and activity levels, no differences in thermal sensation were observed between older and younger people under stable thermal environments and during temperature ramps. However, older subjects exhibited less sensitive than young subjects when suddenly transitioning to cold conditions. Additionally, in subject-controlled dynamic environments, the initial preferred temperature of older people was influenced by their prior thermal state, unlike younger people, while the final preferred temperatures were equivalent between the different groups. Field studies suggest that in real-life living environments involving behavioral and psychological adaptation, older occupants are more likely to express neutral thermal sensation (ratio: 1.83, 95 % confidence interval: 1.53-2.19) and less dissatisfaction (ratio: 0.64, 95 % confidence interval: 0.48-0.87) for indoor thermal environments than younger occupants, and show reduced thermal sensitivity to environmental changes. Limitations of existing studies and directions for further research are also discussed.