Research On Contributing Factors Of Thermal Comfort Improvement Effect Of Vertical Greening In High-rise And High-density Neighborhood

The issue of outdoor thermal comfort in the context of global warming has become one of the major constraints that limit the healthy development of cities.High-density neighborhoods with dense high-rise buildings and limited ground greening are faced with a more difficult dilemma in optimization of thermal comfort.Vertical greening,a new greening method for efficient and intensive use of land with the functions of improving the urban ecological environment and urban landscape,is undoubtedly an effective solution to this dilemma.From the perspective of improving pedestrian thermal comfort,this research explores the best application scenarios of vertical greening in high-rise and high-density neighborhoods.To begin with,give a review on relevant research achievements at home and abroad,including research on urban form and urban microclimate,outdoor thermal comfort,and thermal effects of vertical greening on urban environment.Secondly,summarize spatial characteristics of high-rise and high-density neighborhood and its vertical greening design features,laying foundation for the construction of neighborhood experimental models.Thirdly,introduce the main features and applicability of microclimate software ENVI-met,and construct neighborhood experimental models from three aspects: urban form,wind direction and vertical greening.Environment and material parameters have been set as well.And then,based on the ENVI-met simulation results,use Physiological Equivalent Temperature(PET)to evaluate the thermal comfort improvement effect of vertical greening in different scenarios.And find the laws of the effects of urban form,wind direction and vertical greening design on the thermal comfort improvement of vertical greening.Finally,the above influence laws have been tested and extended in the real urban form of Pazhou West District in Guangzhou.The main conclusions are as follows:(1)The thermal comfort improvement effect of vertical greening decreases with the aspect ratio,and thus vertical greening has a better thermal comfort improvement effect in compact neighborhoods.The essence of the urban form's influence on the thermal comfort improvement effect of vertical greening is that different urban forms produce different forms of wind and thermal environments.(2)Vertical greening has a better effect on improving thermal comfort in the environment with low wind speed or low direct solar radiation,but has little effect on the environment under direct sunlight with high wind speed.(3)The thermal comfort improvement effect under the better vertical greening layout has a positive linear relationship with the Vertical Greening Ratio(VGR),but after VGR reaches a certain level,its positive effect on the thermal comfort improvement is weakened.The design of vertical greening orientation based on the best thermal comfort improvement effect needs to consider the influence of aspect ratio,and vertical greening should be set as close to the height of pedestrians as possible.