Effective Moisture Temperature: Ventilation performance index accounting for effects of air temperature and relative humidity on thermal comfort

Abstract

Relative humidity could be a predominant parameter for thermal comfort. The existing ventilation performance index regarding thermal comfort, i.e., the Effective Draft Temperature (EDT), does not account for the effect of relative humidity on thermal comfort. This study proposes a novel ventilation performance index, i.e., the Effective Moisture Temperature (EMT), to account for the effects of air temperature and relative humidity on thermal comfort. The proposed EMT is defined as an analogy of the EDT and is quantified by the theoretical analysis of the thermal neutrality, boundaries of thermal comfort zone, and equivalent transfer between the relative humidity and air temperature. The proposed EMT is tabulated for practical convenience under cooling and heating scenarios with different thermal comfort requirements. The results based on Monte Carlo simulations and ASHRAE Global Thermal Comfort Database II show that for the low air movement conditions, the accuracy of the original EDT is 23.8%–88.0%, while the accuracy of the proposed EMT is 98.6%–99.5%. This study further develops the Effective Draft and Moisture Temperature (EDMT) for elevated air movement by integrating the EMT and the cooling effect of air movement. For the elevated air movement conditions, the accuracy of the extended EDT is 84.1%–95.5%, while the accuracy of the proposed EDMT is 96.7%–99.2%. The proposed EMT and EDMT contribute to developing thermally comfortable built environments.