An evaluation of three biometeorological indices for human thermal comfort in urban outdoor areas under real climatic conditions

Three biometeorological indices were examined in terms of their potential to describe the actual thermal sensation as this is experienced by humans at areas with different climatological characteristics. The thermal comfort scales, as derived from using Physiological Equivalent Temperature (PET), the Temperature-Humidity Index (THI) and the wind chill index (K), were compared to Actual thermal Sensation Votes (ASV) data as expressed on a 5-point scale. These data were collected by surveys that covered all four seasons of the year and were conducted in seven European cities (Athens, Thessaloniki, Milan, Fribourg, Cambridge, Sheffield and Kassel). Results show that, for any given ASV class, the corresponding classes calculated according to PET, THI and K, present a strong correlation with the climatic mean temperature of the survey site, which in turn leads to misclassification of the thermal sensation. Accordingly, an effort was made to apply an adjustment to the indices based on climatic mean temperature. Only small improvements were observed on the performance of the indices.