Abstract
Dry indoor air has been identified as the main cause of dry skin in winter which greatly affects older occupants' wellbeing, but HVAC design standards are based on average adults and do not specify a humidity level that can prevent dry skin. A field study was carried out to understand the difference between the younger and older people with regards to thermal and humidity comfort and skin condition in winter. The study proves a research procedure that is friendly to and preferred by the participants to measure the effect of the indoor environment on their comfort and skin condition in a real living environment setting. The results suggest that younger and older occupants are different in thermal comfort, specifically older occupants prefer a warmer environment than younger occupants, and the neutral temperature produced by the predicted mean vote method is not warm enough for older occupants. The study also suggests stratum corneum hydration appears to be a good indicator to present the effect of indoor humidity on the occupants' skin condition, which can be used to determine the minimum humidity level to reduce the risk of suffering dry skin in winter.