How Tmrt Affects PET Assessment in Outdoor Environments: A Comparative Study

Many studies explored outdoor thermal comfort in the last several years since it has been strongly related to human health and well-being. The Physiological Equivalent Temperature (PET) is considered one of the most commonly used thermal comfort indexes. It had been approved and applied within different urban spaces and climates. This study is comparative research that explored the importance of using the Mean Radiant Temperature (Tmrt) in the PET assessment. The first method calculated PET based on three measured variables, i.e., relative humidity, wind velocity and air temperature. RayMan software is mainly being utilized to perform this calculation. The second approach calculated PET by combining Envi-met and RayMan. Envi-met allowed four calibrated data, i.e., air temperature (Ta), wind velocity (Wv), relative humidity (RH) and mean radiant temperature (Tmrt). RayMan software used the calibrated results to calculate PET. These methods were explored in outdoor environments at Annaba, Algeria, characterized by the Mediterranean climate. The results showed significant differences in PET values, especially through the warmest times of the day. Certainly, the first method highlighted very high PET values, where 40 ≤PET<51 at noon. At the same time, using Tmrt gave precise PET values (30≤PET ≤32). Based on these findings, we can confirm the importance of considering Tmrt in the PET calculation, which allowed for identifying the accurate comfort range.