Evaluation of thermal sensation among customers: Results from field investigations in underground malls during summer in Nanjing, China

Previous studies on thermal sensation have mainly focused on offices and residential buildings, but rarely on underground malls. In this paper, field studies on thermal environment in six underground malls were conducted in Nanjing, China, particularly from customer's perspective. The results showed that when indoor operative temperature (T-op) was more than 26 degrees C, the customers' mean thermal sensation votes (TSV) were lower than PMV. It indicated that they may perceive the warmth to be less dramatic than PMV predicted in underground malls. When T-op was below 24 degrees C, a higher percentage of customers desired a warmer indoor environment. Customers' thermal acceptability (TA) decreased significantly when relative humidity (RH) increased from 65% to 75% (p < 0.01), and significant changes of TA were recorded when air velocity increased from 0.2 m/s to 0.4 m/s under RH ranging from 70% to 80%. The customers' duration time (DT) in malls were different, the mean TSV of customers with DT less than 1 h was significantly different from other customers' TSV (p < 0.01). Among customers, those who had spent less than an hour in underground mall perceived the thermal environment to be cooler. In addition, the customers' TSV under outdoor-indoor temperature drop in entrance regions in two underground malls was compared. It showed that setting the transitional space with non-airconditioned system or at a slightly higher temperature would improve the customers' thermal sensation and save energy.