Experimental study and evaluation of the thermal environment for sleeping

Thermal comfort while sleeping and sleep quality are closely related to the indoor thermal environment and bed climate. Existing studies have mainly been conducted from the perspective of sleeping structure; little attention has been focused on the influence of bed climate on human thermal comfort, and the role of practical subjective evaluation has been deemphasized. In this experiment, the skin temperature of subjects and the bed climate temperature were measured under different indoor operative temperatures (to), i.e., 11.6 °C, 13.8 °C, 15.8 °C, 18.3 °C and 20.6 °C. The bed climate (BC), pre-sleep (pre-) and post-sleep (post-) indoor thermal environment were evaluated, including the thermal sensation vote (TSV), thermal comfort vote (TCV) and thermal preference vote (TPV), and the sleep quality was investigated. The results showed that the post-TSV index was higher than the pre-TSV index when operative temperature remained above 15.8 °C, while it was lower than the pre-TSV when operative temperature remained not more than 15.8 °C; BC-TSV index invariably remained the highest among the three thermal sensation votes. The gender-specific difference was most pronounced for BC-TSV and least pronounced for post-TSV. Based on the effects of bed climate, the comfortable temperature of the indoor environment was relatively low, and the thermal neutral temperature for males was 1.5 °C lower than that for females. A satisfactory and comfortable thermal condition could be reached when the mean bed climate temperature (MBT) was in the range of 30.2 °C-31.0 °C and the mean skin temperature (MST) remained at 34.5 °C for males and 34.9 °C for females.