Green Roof Retrofit Potential Assessment And Cooling Effect Evaluation

At present,the Urban Heat Island is becoming more and more serious in cities all over the world,the increasing Urban Heat Island strength will not only bring hot weather,but also cause a variety of abnormal urban weather,such as warm winter,hurricane and rainstorm,etc.It will have a large impact on urban climate,industrial production and residential life,especially in hot summer.At the same time,sustained high temperature will cause the increasing of cool electricity consumption and so on,it will not only causing the energy waste,it will further exacerbate the greenhouse gas and human heat release,result in the formation of a vicious circle.As the "fifth facade" of city,green roof has great potential for construction,and relative to the ground green,it has a more prominent role in alleviating UHI,it can also bring from the environment,ecological,economic and social aspects of the comprehensive benefits.However,on the urban scale,there are still lack of scientific assessment of green roof retrofit potential and the environmental benefits:the green roof retrofit potential assessment still not have a set of scientific,perfect evaluation elements system,the quantitative simulation method of green roof cooling effect is also relatively limited at home and abroad.In this paper,we take the Gulou of Nanjing as the study area,based on the RS,GIS and CFD technology,firstly,we built the building information database;secondly,we select the building height,history protection grade,roof forms as the assessment indexes of green roof retrofit potential from the roof microclimate and building physics aspects after systematically combs the relevant technical specifications,research and practice on the green roof construction at home and abroad;thirdly,we take an equal weight of all the buildings in the area with the assessment system and get the quantitative assessment conclusion and spatial distribution pattern of the green roof construction in the area.At last,based on the Computational Fluid Dynamics technology,we use the PHOENICS software to simulate the thermal environment of the study area in two situations:the status quo and the construction of green roofs,at last,the temperature was used as the characterization factor in the simulation results,quantitative assess the green roof cooling effect.Research indicates:(1)It has a high green roof retrofit potential in Gulou,Nanjing,and the suitable construction roof area is about 405.40ha,accounting for about 41.89%of the total roof area of the study area.The spatial distribution has a characteristic:the western area is larger than the east side,among the area,the Xiaoshi Subdistrict,Zhongyangmen Subdistrict and Huaqiaolu Subdistrict all have relatively high suitable retrofit roof area,accounted for the proportion of its subdistrict about 50%.(2)Through the green roof retrofit and construction,it can effectively improve the Gulou District thermal environment status.Specifically,the roof surface thermal environment improvement effect is obvious,temperature reduction range from 1.9? to 16.5 ?;at the pedestrian height(2m),the green roof construction for the improvement of the ground temperature at about 1?;with the building height increase,the green roof's cooling effect for the surrounding thermal environment is gradually weakened.(3)On the roof surface of the small-scale microclimate environment improvement,compared to the building and population-intensive,non-permeability of the underlying area in the city center and high energy consumption of the industrial area,green roof has a better cooling effect in the opening,superior ventilation and a large proportion of underlying surface.At the pedestrian height(2m),in the street canyon,with the openness of the building and the proportion of underlying surface increase on both sides of the street,the green roof's cooling effect will be a slight increase.Based on RS,GIS and CFD technology,this paper explores and constructs the green roof retrofit potential assessment system and evaluates the specific green roof construction potential and the effect of cooling effect on urban scale.Through the quantitative assessment and spatial distribution pattern depiction of green roof retrofit potential,it fill the existence of the two major problems in the current urban green roof construction process,it can provide a systematic framework and methods for reference for the following promotion of green roofs in relevant cities.The whole thesis contains about 40 726 words,49 pictures and charts.