The Research On Thermal Insulation Of Planted Roof In Hunan Areas

Roof greening exerts important influence on improving the quality of indoor thermal environment of building top space and reducing energy consumption of buildings in summer.However,roof greening is affected by geographic factors.Roof greening of different vegetation types have different radiation levels and thickness of covering soil,which leads to the differentiation of indoor heat insulation and energy savings of building top space.For a long term,some research only focus on the influence of sedum lineare,a herbaceous vegetation,on the planting substrate?thermal performance and ecological effect etc..But research into other types of roof greening is so few,and more concentrate in the planting and ornamental.So research on the thermal performance of roofs of different vegetation types under some certain climate circumstances has important scientific meanings and practical values.Based on the reasons above,the author conducted the following research:First,through the study of the basic theory,literature review at home and abroad,from the aspect of plant material,configuration mode,cultivation matrix,eco-efficiency,application technology,experimental study,theoretical analysis and simulation studies etc.,the author understood the development and research of green roofs Home and Abroad,explored theoretical and practical value of this research,and determined research methods and technical route.Second,the author conducted classification and abundant practical research on the roof greening in Hunan Province to better understand the current different situation of the region and abundant practical materials,and found out the current actual problems of roof greening of the region.Third,the author poses the option rules of roof greening in terms of ecological factors and external factors to explain the option standards of vegetation types.Based on the unique natural environment,the author poses the option demands of roof greening that adapts to local climate conditions.Considering the region's botany resource and requirements of roof greening,the rules of seed introduction of climate similarity,and referring to the Technical Guidance Rules of Roof Greening in Hunan,the article selects plant types suitable for the roof greening in the region and ascertains their biological and ecological characteristics and the roof greening types that they adapt to.Fourth,considering the characteristics of solar radiation,the author referred to the energy models of solar radiation,and set up computational models of both direct and scattering solar radiation of building roofs.Based on the radiation rules of long and short waves,the author researched the optical features of plant canopies to set up complete computation systems of long and short wave radiation of planted roofs.The study lays a theoretical foundation for the subsequent analysis of the experimental and numerical simulation.Fifth,in 2014 summer,the author selected six different types of planting roof module and non-planting roofs,respectively five aspects,namely from the inside and outside the roof surface temperature contrast,the roof thermal contrast,the different plant leaf temperature contrast and different air temperature within the plants canopy contrast to conduct a large number of test analysis to study the radioactive characteristics of different types of planted roof summer heat insulation performance and different plants and effects on the outdoor thermal environment,understood the different types of planted roof thermal state law and the internal relationship:the shrubs roof's effect of insulation and cooling is optimal,the trees roof's effect of insulating and cooling is close to the grass roof,the vegetation roof's effect is better than non-vegetation roof;found out the characteristics and major influencing factors of the thermal insulation performance of the different types of vegetation on the roof.As the initial conditions of following simulation,experimental data can also be verified to simulation results.Sixth,through the dynamic simulation analysis methods of building indoor thermal environment and energy coupling,the author applied building energy simulation software EnergyPlus to conduct simulated analysis of planted roof of Changsha,a typical city in Hunan to make quantitative summary of a vegetated roof and obtain the optimal value of key parameters(leaf area index(LAI),soil thickness,insulation layer thickness).The author used the three key parameters as variables and studied their influence to building energy consumption to find out the optimal allocation of energy saving building roof vegetation of residential areas in Changsha.Numerical simulation verifies the accuracy of experimental data and solves the problems that hard to optimize parameters in the experiment due to limited and harsh conditions.This paper provides the means to the accurate prediction and objective evaluation of planted roof insulation performance,and lays the foundation for the formation of optimization design methods of green roof.