The P.E.T. comfort index: Questioning the model

Abstract

This work is a first thorough presentation of the widely used PET (Physiological Equivalent Temperature) comfort index. It underlines the simplifications made in solving the equation system for the PET and proposes a correction of the errors in the widespread version of the PET calculation routine. A comparison of the corrected model with a stringent solving of the equation system is made: as a result, the PET calculated after the original method introduces a bias of −0.5 to +2.3 [K] in the studied conditions (operative temperature, high mean radiant temperature and windy environments).The original vapour diffusion model is also examined and shows no dependency to the clothing level. The comparison with a state-of-the-art vapour transfer model exhibits a significant −7 to +2.6 [K] discrepancy with the corrected PET model in the aforementioned studied conditions. Links to the two versions of the code are provided in the appendix.