Assessment Of The Potential And Cooling Effect For Urban Facade Greening In Xinjiekou District,Nanjing,China

The economy and society have already obtained the fast development with the carry forward of urbanization.Meanwhile,widespread natural landscape types are largely replaced by urban landscape pattern caused by human activities,which have resulted in many environmental problems,such as urban heat island(UHI),urban waterlogging.People gradually transform the admire of the economic construction space to leisure and green space.Residents are more eager to get in touch with nature.Therefore,intensive using limited urban space resources to improve the urban ecological environment and increase urban green volume have become an important option for urban ecological construction and strengthening urban afforestation.However,the contradiction between the supply and demand of green open space in central urban areas has become increasingly prominent.The traditional urban greening methods have been difficult to meet the needs of urban development.How to increase the amount of urban greening and improve the environmental quality of cities are questions that need to be urgently resolved.Vertical greening is a form of greening that adapts to the city's high-density development model.It is an important strategy to relieve the tension of construction site,enhance ecological efficiency and alleviate the negative effects of human activities.However,compared with the construction of vertical greening abroad,the short history of vertical greening research and relevant policies are lagging and missing in our country.The development of vertical greening in China is characterized by low levels and unbalanced local conditions.Therefore,basic research on the potential of vertical greening construction and cooling has been strengthened.Not only is it an effective supplement to relevant research.At the same time,it can provide reference and basis for planning practice and related departments to develop the vertical greening promotion strategy.First,we summarized the limiting factors for construction of green facades locally and internationally.We used the Xinjiekou District Nanjing City in China as a case study area,and selected the wind environment,solar environment,and physical build environment that might impact the potential development of green facades as key factors to quantitatively analyze singly by geographic information systems(GIS)and computational fluid dynamics(CFD).The potential area to develop green facades was assessed through a multi-factor overlay analysis.Second,based on the result of the assessment of the potential for urban facade,several parametric scenarios were developed by means of a three-dimensional microclimate model,ENVI-met4.0,which forecasts the cooling effect and energy saving potential of green facade at the street scale.Finally,some counter measures on the construction of green facade for the Xinjiekou District were put forward on account of the research findings.The main conclusions of this study are as follows:(1)There are at almost two hectares of wall space with ideal characteristics for greening treatments.17726m2 of wall spaces in the Xinjiekou District had a high potential for facade greening,accounting for 30.8%of all exterior wall space under a height of 12m and 17.3%of the entire study area.Sunlight was a key limiting factor in determining whether a green facade should be developed.Irrigation was identified as another important factor that might strongly affect the growth of vertical vegetation in urban environment.The spatial distribution of walls suitable for fagade greening was uneven,with an"inner-high and south-high",spatial pattern.Although vertical greening is not the most efficient way to alleviate urban ecological problems,it is the most effective for urban central districts where construction land is tight.(2)Green facades affect microclimate on hot summer days and mitigate high air temperatures.Three facade greening scenarios were considered based on the assessment of the potential for urban facade,accounting for 8.7%?8.6%?17.3%of the entire study area respectively,and the cumulative value of the cooling effect of the three scenarios is 1.41 ??1.25??2.50? correspondingly.Cooling effect the most two section is before 10 in the morning and evening after for the statistical period,and it's a power function of horizontal distance from the facade greening.The overall cooling effect of facade greening is a simple superposition of parts,and different scenario's overall cooling effect of the same area with different layout is similar,but its internal cooling characteristics are different.The innovation of this paper lies in the single factor evaluation of the factors affecting the vertical greening construction through the use of a combination of GIS and CFD.At the same time,multi-factor analysis method is used to evaluate its potential.Finally,based on the results of potential assessment using scenario analysis to quantitative analysis the cooling effect of vertical greening at the street scale is an effective supplement to the research on the evaluation of the potential of vertical greening construction.It compensates for the lack of quantitative analysis of ecological assessment of vertical greening on the street scale.The research results can provide the basis for the related departments to formulate the promotion strategy of vertical greening construction.At the same time,it also has certain reference significance for similar research and practical work in other regions.The whole thesis contains about 31000 words,32 pictures and charts.