Research On Ecological Benefits Of Roof Greening Based On Modular Design

Under the situation that the urbanization process is accelerating and the ecological envir onment is severe,the ecological benefits of the urban green space system directly affect the quality of the entire urban environment.However,the area that can be applied to urban greening is gradually shrinking,and urban greening construction becomes more and more difficult.The imperative method is to make the greening expand to the space and develop the urban roof greening on the basis of ensuring the existing plane greening.Roof greening has inherent advantages in reducing rainwater runoff,weakening the heat island effect,improving the ecological environment,and improving the quality of human settlements.The construction of the sponge city puts forward higher requirements for roof greening.At present,most of the research on the ecological benefits of urban roof greening stays at the stage of traditional roof greening,and the research on the new technology of roof greening and the ecological benefits it produces is still insufficient.This research innovatively proposes a modular roof greening design method and quantitatively studies its ecological value in terms of cooling and humidifying,optimizing urban rainwater utilization,improving green land coverage,and weakening urban heat island effect,and selecting research areas to complete roof construction.After the assessment,the large-scale simulation application of modular roof greening is carried out to analyze the ecological benefits under the larger city scale,and provide reference for the promotion and construction of new roof greening in Chengdu,and further promote the development of urban roof greening.The main research results are as follows:(1)The greening modules of the three designs have different ecological benefits in terms of rainwater utilization,cooling and humidification,and carbon fixation and oxygen release.In terms of rainwater utilization,the rainwater Evaporation of the Lobelia greening module is the largest,followed by the Taiwan No.2 greening module and the Buddha grass greening module;in terms of cooling and humidification,the strength is in turn the Buddha grass greening module>Taiwan No.2 Greening Module>the Lobelia Greening Module;In terms of carbon sequestration and oxygen release,the Lobelia Greening Module has the strongest ability to absorb carbon dioxide and release oxygen,followed by the Taiwan No.2 greening module,and the carbon release capacity of the Buddha grass greening module is the worst.(2)Comprehensive evaluation of the ecological benefits of the greening modules of three different plant materials,found that the ecological benefits of the Buddha grass greening module are the best,followed by the Lobelia Greening Module and the greening module of Taiwan No.2.Therefore,the Buddha grass greening module was selected for the simulation application of modular roof greening in the later study area.(3)Based on geographic information technology,investigate and analyze the building roof,roof greening and heat island effect of the research area,Chengdu Red Card Building Area.the results show that the total area of 494 buildings in the area is 30.9 hm~2,which is about 22.1%of the total area.83 building roofs contain roof greening.In the existing green roof,the roof area utilization rate is 24.2%,the green area is 1.78 hm~2,accounting for 5.8%of the total building roof area,and the roof green coverage rate is only 1.3%.Most of the roof greening is part of the green area,and the full use of roof space resources is not realized.About one-third of the area in the study area has a temperature above 29.86°C,about two-thirds of the area has a temperature above 29.02°C,and the lowest temperature range of25.92-26.2°C covers only 10%of the total area.(4)A modular roof greening assessment was made for the building roof of the study area,The results show that there are 225 buildings with modular roof greening,covering an area of12.9 hm~2,accounting for 42%of the total roof area;there are 269 buildings without modular roof greening,covering an area of 17.9 hm~2,accounting for 58%of the total roof area.(5)The research area after the modular roof greening simulation application will increase the green area of 11.2 hm~2,accounting for 42%of the total roof area,while the roof green coverage rate will increase from 1.3%to 9.3%.In the summer,the area can use rainwater reach to 288.9 m~3,absorb 200.6 kg of carbon dioxide and release 153 kg of oxygen.And the temperature of the area decreased significantly,after greening,the area of the lowest temperature range has increased to about 50%of the total area.It is concluded that modular roof greening will generate huge ecological benefits,and large-scale promotion should be implemented in the future of the roof greening construction.