The sleeping thermal comfort model based on local thermal requirements in winter

Conditions for thermal comfort are different between awake and sleeping state of the human body in winter due to the reduction of metabolism, the increase in thermal resistance and the limitation of movement region. The human body could be segmented into head and covered body in terms of different thermal environment exposure during sleep, and the thermal requirements would vary between the two segments both in physiological and psychological aspects. Current sleeping comfort models provide references for thermal environment design and evaluation based on lumped concept, and the thermal requirement variation between different local parts was overlooked. In the present study, the partial thermal sensation and whole percent dissatisfied model (PTS-WPD model) for sleeping thermal comfort was developed based on the heat balance of human body. The PTS model provided the local thermal sensation for head and covered body during sleep, and the WPD model integrates each separate local thermal sensation into synthetic indicator for thermal environment evaluation. The predicted results by PTS-WPD model agreed well with the experimental results. Coupled thermal comfort zones of indoor thermal environment and bed climate were established by solving the comfort model. It was indicated that the indoor temperature could be reduced by proper increase of bed temperature. The study has important implications for on-demand thermal environment regulation and building energy conservation.