Field study of cold radiant asymmetry caused by exterior built elements of educational buildings in severe cold area, China

Abstract

In winters of the severe cold areas, low surface temperatures of exterior building elements (both opaque and transparent) can easily cause cold radiation to the indoor environments and lead to local discomfort of inhabitants. Therefore, not only the non-condensation on the walls is required in the building thermal design, but also the demand to satisfy human thermal comfort should be considered. In recent winters, we have conducted a field survey and subjective questionnaire in the non-uniform indoor environments in Harbin. Particularly, educational settings were focused and the subjects were all college students. Besides, local thermal sensations of the subjects were asked in the questionnaire. The samples when the subjects were in a thermally neutral state were selected for further analysis. The results indicated that the radiant temperature asymmetry was less than 3.5 °C in 80% of samples. In the cold asymmetric environments, the lower limbs were more sensitive to coldness than the rest parts of human body. The overall thermal sensations of subjects were not equivalent to the PMV indices (Predicted Mean Vote), but showed a pronounced linear relationship with their thermal comfort and thermal acceptability, separately. In addition, accepting that 5% of subjects may feel uncomfortable, a radiant temperature asymmetry of 2.3 °C was acceptable for the horizontal asymmetry. The study exhibits human thermal comfort of whole and local body parts in the non-uniform environments and gives a guide for thermal design of exterior wall insulation.