Numerical Investigations on the Impact of Greening on Outdoor Thermal Comfort for Different Scale Residential Blocks

Residential areas are the basic unit related to the living quality of urban residents, and their comfort is one of the key concerns of residents. Greening has always been an important means to improve the living environment of residential communities. In this paper, ENVI-met V4 simulation software is verified and used to discuss the influence of the residential scale and green ratio on the outdoor thermal environment. By comparing the difference in outdoor thermal comfort with or without greening measures in residential blocks of different scales, the effects of vegetation on optimizing the outdoor thermal comfort of different scale residential blocks are investigated. The meteorological parameters selected for this case study analysis include a wind speed of 2.5 m/s at 10 m height and an air temperature range of 28 °C to 35 °C. The results show that the wind speed and air temperature in the residential area are less affected by the residential scale and more affected by the greening rate. There are obvious differences in the improvement in outdoor thermal comfort by vegetation at different times. With the increase in residential area scale, the improvement effect of vegetation on outdoor thermal comfort also increases, which in 5 × 5 blocks residential area is 0.2–0.5 °C, higher than that in 2 × 2 blocks small-scale residential area. A modified index, PET (Physiological Equivalent Temperature) drop per green ratio, is proposed for cost performance. Reasonable and feasible greening suggestions for residential buildings are summarized.