Assessing the Indoor Thermal Comfort and Adaptive Behaviours of Older People in the Residences of Warm and Humid Climate, India

Population aging, extreme weather conditions, and rising energy costs present significant challenges, especially in developing Asian countries like India. A key sustainability goal for future age-friendly cities is to ensure that older adults live in housing tailored to their specific needs. However, existing thermal comfort studies in India often treat the adult population as homogeneous, overlooking the unique thermal comfort requirements of the older people. This study addresses this gap by examining seasonal variations in indoor thermal comfort and associated behavioural adjustments among older adults in their residences of warm and humid climate of India. Data were collected from 1,480 respondents through a longitudinal survey and simultaneous measurements of indoor environmental variables. Linear regression analysis revealed that comfort temperatures (TSV ±1) for the older people are 30°C in summer, 28.1°C in winter, and 29.2°C overall. The steeper slope of the summer regression indicates that even minor increases in indoor temperature significantly affect thermal sensations, highlighting the difficulties older adults face in warmer months. At a prevailing mean outdoor temperature (PMOT) of 25°C, the comfort band for older individuals ranges from 26°C to 31°C. Under ASHRAE 55-2020 conditions (TSV ±0.5), the comfort range is 26.9°C to 29.7°C. Notably, the comfort range for older individuals in this study is narrower compared to IMAC R, IMAC NV, and ASHRAE 55-2020 models, with a regression slope of 0.56 indicating heightened sensitivity to temperature variations. Additionally, relative importance index analysis shows that older males favour active cooling measures in summer, such as wearing lighter clothing and seeking airy spaces, while females prioritize modifying daily routines. In winter, both genders adopt warming strategies, with males emphasizing hot showers and females choosing heavier clothing.