Influence of outdoor and indoor microclimate on human thermal adaptation in winter in the severe cold area, China

Harbin is in the severe cold climate zone in China, where the outdoor air temperature is low in winter. The central heating system without terminal control is used in buildings in the area. A field study on thermal comfort was conducted in four types of buildings in Harbin during a same winter. Due to the broad range of outdoor air temperatures and the long heating period in Harbin winter, the heating period was divided into three stages. We focused on indoor thermal environment and human adaptability during the three phases. Some environmental parameters were measured together with subjective investigation, and totally 1747 valid questionnaires were collected. The results show that indoor temperature over 24 °C often occurred in the buildings during the heating period. The occupants felt warm but they expected the indoor temperature no change. The participants were more sensitive to temperature variations at the early heating phase (EH). They adapted to warm environment gradually from EH to LH. The occupants would open windows when indoor temperatures were high. Great energy savings could be achieved by reducing indoor air temperature in winter. The neutral temperatures were lower than the indoor air temperatures in the buildings, indicating that indoor temperatures were sometimes overheated. The indoor temperature should be reduced to the lower limit at EH and increased gradually in winter. The neutral temperatures in offices and university classrooms were lower than those in apartments and dormitories. Therefore, lower indoor air temperatures are recommended in design of public buildings for space heating.