Investigation into the differences among several outdoor thermal comfort indices against field survey in subtropics

Comfortable and healthy outdoor microclimates are beneficial to sustainable urban development. Based on a comprehensive comparison of some currently frequently used thermal comfort indices, including PMV, WBGT, PET, SET*, and UTCI, the differences among these indices are significant in dealing with the fundamental energy balance model, descriptive equations, and application boundary conditions. In order to validate these indices, a subjective questionnaire survey with field measurements was carried out on a university campus in Guangzhou in southern China. Results revealed strong linear relationships between operative temperature and mean radiant temperature (T-mrt), WBGT, PET, SET*, UTCI, as well as PMV. However, the relationships between these thermal comfort indices and the mean thermal sensation vote (MTSV) are not clear for a hot outdoor environment, especially when the operative temperature was above 34 degrees C. The ranges of the heat stress category and PMV need to be modified for the evaluation of hot outdoor environments.