Thermal sensation, sick building syndrome symptoms, and physiological responses of occupants in environments with vertical air temperature differences

Abstract

Vertical air temperature differences (VTDs) can have important influences on thermal comfort and the evaluation of air distributions. The air distributions might create either positive or negative VTDs. However, no research has clearly revealed the effect of different directions of VTDs on human comfort. To create environments with positive and negative VTDs in this study, the air temperature of half of the body was maintained at an air temperature of 25 °C, whereas the other half of the body (the upper or lower body part, respectively) was exposed to air temperatures of 22 °C, 25 °C, 28 °C, and 31 °C, respectively. That is two series of experiments with the same VTD value but different directions were compared, based on 16 subjects seated in a climatic box in a climate chamber. The thermal sensations, sick building syndrome (SBS) symptoms, and physiological responses of occupants were studied. The results showed that subjects were more sensitive to the VTD at the upper body part in warm environments with respect to thermal sensations, perceived air quality, and sweat intensity. The analysis indicated that there were more discomfort and heat stress for positive VTDs than negative VTDs. Thus, the criterion for acceptable negative VTDs should be different with the positive VTDs incorporated in current standards. Overall, the directions of the VTDs were suggested to be considered for evaluating the thermally stratified air distributions based on both of thermal comfort and energy efficiency in buildings.