Effects of a heat wave on short-time acclimatization during experiments supported by a climate chamber

Abstract Studies on human thermal comfort in open areas are relevant for climate-responsive urban design, as they are closely connected with the quality of life in urban areas. Considering the increasing frequency of heat waves in such areas, their effect on thermal perception of urbanites should be evaluated. This study analysed the effects of short-term acclimatisation on the thermal perception of individuals in open spaces during heat-wave episodes. Steady-state conditions were ensured by a prolonged stay of participants (N=16) in a test chamber prior to the subjects' exposure to the outdoors, in Karlsruhe, Germany. Questionnaire wer administered as regards thermal sensation and preference at three time stamps: a) immediately after leaving the chamber, b) 15 minutes and c) 30 minutes after that. We evaluated acclimatisation effects on the subjects' thermal perception against predictions of the outdoor thermal conditions in terms of UTCI (Universal Thermal Climate Index) and the derived DTS (Dynamic Thermal Sensation). The results showed that, although outdoor conditions remained unchanged throughout the 30-min exposure time, the subjects' thermal perception votes differed slightly with time of exposure, albeit with no statistical significance. Acclimatisation to heat wave leads to enhanced heat tolerance just after it, with acclimatisation loss in the subsequent session.