Comparison of human thermal responses between the urban forest area and the central building district in Seoul, Korea

• We evaluated the amelioration effects of urban forest on human thermal comfort.
• Comfortable air temperature range in the forest area was wider than in the urban area.
• Skin temperature in summer in the forest area was 1 °C lower than in the urban area.

This study elucidated the thermal effects of urban forests on physiological and psychological responses; changes in skin temperature, thermal sensation, and thermal preferences. The air temperature, relative humidity, air velocity, and globe temperature were measured in an urban forest and a central building district (CBD) area. Changes in skin temperature were analyzed for 12 subjects in both areas. A total of 790 individuals were interviewed on the actual thermal comfort. The results showed that air temperature and outdoor standard effective temperature (OUT_SET*) in the summer and autumn were higher at the CBD than at the urban forest area (p < 0.01). In summer, the mean skin temperature was 35.0 °C at the CBD and 34.0 °C at the urban forest area, respectively. In autumn, it was 33.3 °C and 31.3 °C. During the summer, 60.3% of participants felt hot sensation in the CBD (23.8%, in the forest), while 79.3% felt comfortable in the urban forest (31.1%, in the CBD). The comfortable air temperature range in the urban forest area was 12.1 to 21.6 °C, it was broader than in the CBD. People in the urban forest area felt more comfortable than did those in the CBD. These findings suggest that urban forests increase thermal comfort and widen the comfortable temperature range.