Energy efficient thermal comfort in temporarily occupied space – A summer case study in Tianjin

Temporarily occupied space is defined as an air-conditioned space in which most of occupants stay for less than a certain period (e.g., 40 minutes) such as post offices, supermarkets, bookstores and banks. After moving from a hot and humid outdoor environment to an air-conditioned temporarily occupied space in summer, thermal alliesthesia takes effect, which refers to ‘thermal pleasure sensation and overshoot generated by the restoration of thermal stress toward a neutral interior condition’. Because of the overshoot, occupants’ acceptable temperature ranges in temporarily occupied space are possibly elevated by less intensified air conditioning systems while they still feel comfortable. To address this issue, a human subjective response study was performed in one climatic chamber used to simulate temporarily occupied space in Tianjin. 16 healthy university students, 8 males and 8 females, were exposed to outdoor environment for 20 minutes before they stayed in the chamber for 40 minutes. Their votes on thermal sensation, comfort and preference were recorded for evaluation at different time points. The results show that, in summer, the optimal design temperature range for temporarily occupied space in Tianjin is elevated to 27 °C to 29 °C without influencing thermal comfort, enabling large amounts of cooling and dehumidification energy to be saved for air-conditioning systems. Meanwhile, thermal comfort for staffs who have long term exposure to the environment could be maintained by personal comfort systems such as desk fans or personalized ventilation in terms of spatial alliesthesia