Effect of Greening Trees on Thermal Comfort of the Pedestrian Streets in Hot Summer and Cold Winter Regions in China

Abstract

The thermal environment problems of pedestrian streets space are becoming increasingly important with the growing rate of urbanization, especially in regions with hot summers and cold winters. Taking Cinnamomum camphora as an example, several urban design scenarios with dynamic setting parameters of streets orientation (N-S, E-W), aspect ratio (0.5, 1,1.5, 2) are simulated by ENVI-met to analyze the impact of the green coverage on the thermal comfort of the street canyons in Shanghai. Results showed that: (1) green coverage has an impact on the thermal comfort of the street both in summer and winter and the significance of this effect is affected by the orientation and aspect ratio of the streets. (2) In summer, with the increase in aspect ratio, N-S orientation streets need more and more green coverage to bring a significant impact on thermal comfort, while E-W orientation streets only need 24 % green coverage. (3) In winter, with the increase in aspect ratio, N-S orientation streets also need more green coverage to significantly reduce thermal comfort. For E-W orientation, only when the aspect ratio is 1/2, the green coverage can effectively reduce the thermal comfort of the street. (4) The planting layout had no significant effect on the thermal comfort effect of trees. Based on the above conclusions, the greening strategy was proposed for pedestrian streets in the hot summer and cold winter region in China.