Local thermal comfort chart for non-uniform building environments: Comparison with vehicle environments and its application

Abstract

There have been many laboratory studies of human subjects exposed to non-uniform thermal environments such as radiant temperature asymmetry from different directions, vertical air temperature differences, and draught. However, there are no final conclusions on the unified quantitative index for general non-uniform environments, which will be stressed in this study. The equivalent temperature (teq) that integrates air temperature, radiant temperature and air velocity at different body parts and well relates with thermal perceptions is adopted as an integral evaluation index. Published data from laboratory measurements of office environments with subjects exposed to different types of radiant asymmetry and measurements with a thermal manikin were analysed. A new comfort chart of teq was developed to evaluate non-uniform building environments and it was compared with the existing comfort chart (in ISO 14505) applied in vehicle. The results indicated that overall sensible heat loss of the human body remained constant, but local thermal discomfort and sensation changed with the non-uniform environments. The new comfort chart identified the source of discomfort and predicted the observed subjective evaluations. Significant discrepancy of the comfort chart between buildings and vehicles was found, indicating the necessity of developing a comfort chart that applied in the building environment. The study provides new insights into the causes of local thermal discomfort and can provide information on the sensitivity of different body parts to heat loss that can be used to optimise the thermal design of indoor environments.