Research On Structural Optimization Of Composite Planting Roof And Comparative Test Of Thermal Insulation Performance

With the continuous development of urbanization,people have to face increasingly severe environmental and energy issues.According to research,building energy consumption has accounted for about 30%of the total energy consumption in the society.Reducing building energy consumption and improving the comfort of the building environment have become an urgent issue that people need to solve.Roof insulation as a building passive insulation technology could reduce the heat transferred from the roof to the interior,thereby reducing air conditioning energy consumption.In the roof insulation technology,the planted roof has an important role in the roof insulation technology with its unique ecological advantages.Compared with ventilated thermal insulation roof and thermal insulation roof,planting roof has the advantages of reducing heat transfer of roof,slowing down urban heat island effect,improving building roof environment,accumulating rainwater,reducing urban surface runoff,and extending roof service life.However,the traditional planting roof has the problem that the heat storage of the planted soil layer during the day was too large due to the absorption of solar radiation,and the heat dissipation rate was slow at night,resulting in the temperature of the planted soil layer being too high and the reverse heat transfer to the room.In addition,there are problems such as low utilization rate of water storage accumulation and unstable thermal insulation effect.These problems have plagued the application and promotion of planting roofs.In order to solve the above problems of traditional planting roofs,four new compound planting roofs were designed in this paper.Based on planting roofs,the characteristics of water storage roofs and ventilated roofs were combined to form a new compound planting roof insulation mode.The thermal insulation performance under actual climatic conditions was compared with the traditional thermal insulation roof.In this experiment,8 kinds of thermal insulation roof modules with different structures were established,including 4 composite planting roof thermal insulation modules and 4comparative test modules.The experimental platform was established in Guangzhou.By collecting the test data during the continuous sunny period,the thermal insulation performance and thermal insulation characteristics of different structural modules were compared and analyzed.Provide basic experimental basis with engineering application.Compared with the four types of comparative testing roof modules,the compound planting roof module could effectively improve the thermal insulation performance of the roof.In summer test conditions,the average temperature of the bottom surface of the test module from high to low is ranked as bare roof>ordinary planting roof>roof pond>ventilation roof>Aerial mechanical ventilation planting roof>Compound water storage planting roof>Aerial natural ventilation planting roof>Compound water storage ventilation planting roof.It reflects that the compound planting module has better thermal insulation performance than other modules.Under the three test conditions,the average temperature amplitude of the compound planting module is less than 2?,and the heat flow peak and valley difference are less than 3 W/m~2,while the heat flow peak and valley difference of the comparative insulation roof module is about 10W/m~2,this reflected the compound planting roof has a good heat flow reduction ability and anti-interference resistance to the impact of the external environment.Among the compound planting roof modules,the compound water storage and ventilation planting module(module G)has the best thermal insulation performance.This phenomenon reflects that setting ventilation in the soil layer of the compound planting roof could effectively improve its heat dissipation performance,and improve thermal insulation effect.Under the test conditions in summer,the module G has a cooling range of 12.2?33.2?compared with the bare roof,and could reduce the heat flow into the room by 64.2%.Establish the heat balance equation of the compound planting roof insulation module,and solve it by numerical analysis.The average relative error between the theoretically calculated value of the soil layer temperature and the actual test value of the compound planting roof insulation module is between 3.8 and 11.4%,and the maximum relative error is between 10.2 and 23.2%.Under different test phases,by comparing the actual test value with the theoretical calculation value,the fit of the overhead mechanical ventilation planting module(module D)and the storage ventilation planting module(module G)is good.The main reason for the error may be that the effects of soil layer moisture content and plant vegetation growth are not fully considered.