The impact of street geometry on outdoor thermal comfort within three different urban forms in severe cold region of China

This paper focuses on the influence of urban morphology on pedestrian outdoor thermal comfort in Harbin, located in the severe cold region of northeast China. Three typical districts with different urban densities and street layouts were investigated. Field measurement and thermal comfort questionnaire survey were carried out from July 2020 to January 2021. Regression analysis was performed and the neutral physiological equivalent temperature (PET) range was 14.5–22.8 °C. In addition, the PET range was 7.9–27.3 °C when 80% of thermal votes were “acceptable”. ENVI-met was verified and utilized to assess the mesoscale and street-scale impact of urban morphology on thermal comfort in hot and cold seasons. Measurement results shows that the PET variation caused by urban morphology was more significant in the transition season, with the maximum PET difference of 7.6 °C observed at the mid-rise district and the minimum value of 4.4 °C in the low-rise area. Simulation results indicate that the average building height significantly affects the background Ta and PET distribution within the block. Mean radiant temperature (MRT) and PET are highly correlated to sky view factor (SVF) in summer, while in winter, PET is related to SVF only in the low-rise district. Based on the thermal comfort calendar in both hot and cold seasons, shallow and medium canyons (0.5 < H/W < 1.5) are more favorable in severe cold climate, and the optimum streets are near the N–S orientation, followed by intermediate orientations, while deeper canyons (H/W > 1.5) are not recommended due to the lack of solar absorption.