The Cost And Ecological Benefit Analysis Of Green Roof In Guangzhou

With the accelerating process of urbanization, urban landscaping ratio is on the decrease. So, the attention is paid to the ‘fifth side’ of building which used to be ignored. That is the green roofs. This paper analyzed cost benefit and ecological benefit from the perspective of technology, economy, ecological environment, apply strategy and so on. And, some suggestions are put forward to popularize green roof, in accordance with the problems and situation analysis in Guangzhou.In the 3 methods of green roofs, the lawn roof has the advantages of low cost, light weight and easy maintained. It is suitable for promotion in large scale. Then, a office building in Guangzhou was selected as a case study. The construction cost of roof greening project is about 40680 yuan. Combined with the meteorological conditions in Guangzhou, energy saving benefit of green roof was calculated by Ecotect. This project could save 2314.7 k W·h per year and 9.64 k W·h/m2. From the calculated cost and saving electricity above, the cost benefit of this project was analyzed. And the dynamic investment pay-back period is more than 30 years on the condition of no government subsidy.After the cost benefit analysis from micro level, qualitative and quantitative analysis of ecological benefit were done from macro level. There’s about 70 million m2 roofs in Guangzhou city. If one-third roofs are greening, it could save electricity about 0.225 billion k W·h, reduce 164.6 thousand t carbon emission, absorb 72.3 t harmful gas, reduce 3498 t dust per year. At the same time, the plant could absorb 933.3 ton CO2 for the photosynthesis.Ecological benefit is remarkable.At last, aiming at slow development of green roofs and existing problems in Guangzhou, the main reasons were found by field research. They lie in 3 aspects: ambiguous property rights, lack of money and architectural design didn’t consider roof greening. So, based on the experience of foreign management and technologies, some suggestions are put forward to popularize green roofs on a large scale in Guangzhou.