Compliance with limits of acceptability for thermal comfort, and implications for long-term comfort

Abstract

This paper illustrates the derivation of a method to check whether conditions in a given indoor work environment comply or do not comply with the relevant limit of acceptability for thermal comfort. The proposed method advocates that measurement uncertainties should be ignored, as they are way too large for consistency with the existing scheme of closely-spaced thermal categories outlined in international standards. It focuses instead on the identification of a representative value of the synthetic thermal comfort index PMV to be compared with the limit of acceptability. Because indoor thermal environments, even when air-conditioned, exhibit non negligible daily and seasonal fluctuations, care must be taken to ensure that this representative value of PMV reflects thermal conditions approaching the worst case. Because the actual distribution of PMV in a given environment is unknown, the distribution of the outdoor temperature Tout is used as a proxy, and a representative value of Tout is identified in terms of a specific quantile of the summer/winter distributions. This implies that PMV can be considered adequate for comparison with limits if based on measurements carried out when the outdoor temperature is near a specified quantile of the summer/winter distributions.As a byproduct, results have been used for improving the existing methods for evaluation and assessment of long term comfort. To this aim, a more appropriate expression for weighting different exposures has been derived, and a limit of acceptability has been identified.