Parametric study on the sleep thermal environment

Sleep thermal environment has a great effect on occupants’ sleep quality. The purpose of this study was to explore the relationships between sleep thermal environment parameters and sleep quality in winter and summer. The whole experiments involved indoor ambient temperatures (winter: 17 °C, 20 °C, 23 °C; summer: 23 °C, 26 °C, 29 °C) and relative humidity (RH; winter: 40%, 55%, 70%; summer: 40%, 60%, 80%). A total of 18 young subjects (23±2 years old) were divided into the two different season groups to experience the corresponding environmental conditions. Their subjective environmental perception and objective physiological signals were monitored. The results showed that thermal sensations at 20 °C in winter, as well as 26 °C in summer, were considered as the thermal neutral states. Humid sensation in winter before sleep was susceptible to SET*, while the middle value of SET* (32 °C) related to the middle indoor air temperature (26 °C) and air humidity (60%) before and after sleep could be the summer combination of neutral thermal environment. Furthermore, cold and wet environment in winter was found to seriously affect the deep sleep. In summer, mild temperature contributing to good sleep quality might weaken the effect of humidity on sleep. Through combining the sleep environmental perception result with contour line and regression analysis on objective sleep quality, the suggested values of thermal environment parameters for young adults (21–25 years old) were as follows: 20.3 °C and 56%RH in winter, as well as 26.1 °C and 52%RH in summer.