Exergetic aspect of human thermal comfort and adaptation

Abstract

This chapter describes why passive-technology measures such as better thermal insulation of exterior building envelope systems and more efficient solar control of window systems come to the top priority, from the findings available from a series of human-body exergy research. The human-body exergy consumption rate varies very much with the change in mean radiant temperature, and there is a value of mean radiant temperature giving the smallest possible human-body exergy consumption rate under a chosen set of air velocity and air temperature indoors. In such a case, where room air temperature is higher than the conventional target value in mechanical air cooling, the smallest possible human-body exergy consumption rate emerges with the mean radiant temperature ranging between 26 °C and 29 °C. This result suggests that the first priority for summer seasons especially in hot and humid climate regions is to reduce solar heat gain from windows by external shading and from electric lighting and others in order to make the mean radiant temperature stay sufficiently low, but not too low. Such control of indoor radiant environmental condition, which is primarily to be done by passive-technology measures, should allow building occupants to take rational adaptive behaviour such as window opening and thereby to perform natural ventilation. Provided that the rational passive-technology measures are taken, then right-sized radiant cooling systems should also function effectively with the use of natural exergy resources.