Human responses to high humidity in elevated temperatures for people in hot-humid climates

The impact of high humidity at high temperatures on the thermal and humid responses of people in hot-humid climates is critical for ensuring a suitable indoor environmental quality and promoting the energy efficiency of buildings. Thirty healthy young people (15 males and 15 females), who were born and raised in hot-humid areas of China, were recruited as subjects. Six experimental conditions with high levels of air temperature (Ta) and relative humidity (RH) (29°C/50%, 29°C/70%, 29°C/90%, 32°C/50%, 32°C/70%, 32°C/90%), with one extreme hot condition and two cool conditions, were tested. Both psychological and physiological responses were collected. The results indicate that the impact of humidity on human responses was not significant when the relative humidity was below 70% and was significant and increased with an increase in air temperature when the relative humidity was above 70%. The relationships between the thermal and humid responses and the ET* or RH were identified as linear or polynomial functions. The upper limit for people in hot-humid climates who engaged in sedentary activity and dressed in summer clothing (0.57 clo) was determined to be 30.3 °C in ET* for the 90% acceptable range and 32.3 °C in ET* for the 80% acceptable range. This study provides useful information for the humidity requirements of indoor environments in hot-humid climates.