Differences in the elderly’s behaviour pattern of using room air conditioners between the normal and extremely-hot summers – A case in Chongqing, China

[Display omitted] •Elderly’s thermal demand in the extreme and normal conditions were compared.•Indoor environment maintained was 2 °C warmer in the extremely-hot summer.•RAC operation duration in the extremely-hot summer was 2.4 times higher.•The daily average RAC temperature setpoint was 2 °C higher in extremely-hot summer.•RAC operation pattern was classified for the extremely-hot and normal summers. Given the higher frequency and intensity of climate extreme events, it is crucial to understand the indoor thermal demand of the elderly and the changes in controlling indoor thermal environment during extremely hot and normal summer conditions. In order to determine the disparity in the elderly’s indoor thermal demand during extremely hot and normal summers, this study conducted field investigations with thirteen elderly subjects in a care home in Chongqing, China. The indoor and outdoor thermal parameters were continuously measured, and the operation of their room air conditioners (RAC) was remotely monitored. The results revealed that the daily average indoor air temperature was approximately 2 °C warmer during the extremely hot summer, but it could be even warmer in some cases of the normal summer. The operation duration of room air conditioners during the extremely hot summer was 2.4 times higher, but the rate of room air conditioner activation was higher in the Before-dawn period in the normal summer, suggesting potential sleep disturbances due to unexpected heat at normal-summer nights. The daily average RAC temperature setpoint was 28.8 °C during the extremely hot summer and 26.7 °C during the normal summer, and the daily average temperature setpoint during the extremely hot summer showed a significant positive correlation with outdoor temperature and daily operation duration. Based on the RAC usage pattern classification, the short-term and moderate-cooling pattern was preferred by the elderly subjects during the extremely hot summer.