Performance evaluation of long-term thermal comfort indices in building simulation according to ASHRAE Standard 55

Arthur Santos Silva, Enedir Ghisi, Roberto Lamberts
Building and Environment

The objective of this study is to analyse long-term indices for thermal comfort evaluation according to ASHRAE Standard 55 for low and elevated air speed models. This study comprehends the development and validation of scripts for calculating PMV/PPD, a sensitivity analysis of the input variables and identification of important sample regions which can cause thermal discomfort. A simulation experiment was performed using the EnergyPlus computer programme considering uncertainties in the metabolic rate, air speed, clothing insulation and air-conditioning set point temperatures in each zone of a hypothetical office building in Brazil. A total of 37 long-term thermal comfort indices were used for assessing the thermal comfort performance of each zone. Indices were divided into: percentage outside range of PMV and operative temperature; exceedance hours of PMV and operative temperature; degree-hour criterion of operative temperature; PPD-based; PPD weighted criterion; and operative temperature weighted criterion. The simulation experiment has shown that the different indices for long-term evaluation lead to different results but similar trends. High uncertainty was obtained which can compromise comparison of different cases. Some long-term indices were recommended for using in building simulation assessment, as well as a different index which includes both degree-hour severity of discomfort hours and PPD non-linear weighting. The difficulty in choosing an ideal index is discussed and an alternative is shown by using two or more indices to enable the correct assessment and comparison of different cases.