Thermal comfort and sleep quality under temperature, relative humidity and illuminance in sleep environment

This study dealt with the effects of environmental factors on thermal comfort and sleep quality. Based on orthogonal experimental design method, chamber experiments were assigned to conduct nine groups of cases through the combinations of temperature (17°С, 20°С, 23°С), relative humidity (40%, 55%, 70%), and pre-sleep as well as pre-awakening illuminance (30 lux, 90 lux, 150 lux). In each case, environmental perceptions were evaluated and physiological measurements were recorded during the whole nights. After further analysis combining the subjective and objective results, it can be concluded that temperature is the main factor affecting sleep quality compared with relatively insignificant effects of relative humidity and illuminance. In addition, case E (20°С, 55%, 150 lux (pre-sleep illuminance), 30 lux (pre-awakening illuminance)) can be a proponent combination improving sleep quality subjectively and objectively among the nine cases. Especially, 20°С with the specific bedding system is better for sleep quality among all levels within investigated environmental factors. Meanwhile, the result of subjective sensations in thermal environment reveals the intimate relation between thermal comfort and sleep quality. Although illuminance was not found obviously to affect sleep in the setting experimental environment due to the insufficient sample size, it would not weaken the significance of light environment in the comprehensive sleep environment.