Study On Energy-saving Reconstruction Scheme Of Residential Building Envelope In Lhasa Area

With the rapid development of China's economy,building energy consumption has become one of the main energy consumption in China.Therefore,the building energy efficiency design and transformation has become an important direction for the sustainable development of our architecture.In view of the relatively backward economic development in Tibet,and the gradual improvement of the indoor thermal comfort requirements of the local residents,based on the abundant solar energy resources in Lhasa,this paper studies single energy-saving and comprehensive energy-saving transformation programs of the external structure of the existing residential buildings in this area,in order to improve the energy saving,economy and indoor thermal comfort of existing residential buildings in the region.In this paper,the main research is based on the residential building of the People's Government in Dongga Town,Duilong County of Lhasa.First of all,for the external walls,roofs,southern and northward windows in the outer envelope,using the individual variable control method and building energy consumption simulation software called “DesignBuilder”,the article does energy consumption simulation of individual energy saving reconstruction scheme for exterior envelope,and determines energy-saving materials,its economic thickness of external wall and roof insulation layer by the energy saving,economy and indoor thermal comfort analysis of building heating.Then,on this basis,applying orthogonal experimental method,to formulating simulation programs of external envelope comprehensive energy-saving transformation,this paper ensures the best combination scheme of northern and southern exterior walls layer thickness,roof insulation layer thickness on the comprehensive energy-saving transformation,through the use of “DesignBuilder” software to perform heating energy consumption simulation,building heating energy saving,economy,extreme analysis,indoor thermal environment analysis and other methods.Finally,the whole analysis methods and the transformation plans are comprehensively evaluated and compared.This thesis draws the conclusion: among three kinds of envelope insulation materials of Extrusion Polystyrene Board(XPS),Expanded Polystyrene Board(EPS),and Rigid Polyurethane Foam(PUR)in its life cycle,the material corresponding to the minimum cost is XPS for individual energy-saving transformation of external walls and roof insulation.The corresponding thickness is 20,30 respectively,and the corresponding total cost is 23.8yuan/m2,49.5 yuan/m2.In Lhasa,building's design or transformation,the southern windows should be hollow glasses and their areas should be increased,however,northern ones should use Low-E glasses,their areas should be reduced,and they will have better insulation effect.We order the impact of heating energy consumption from large to small on outer envelope of residential building in Lhasa area,they are northern outer window transformation,southernouter window transformation,northern external wall insulation,roof insulation,and southern external wall insulation.The optimal program of integrated energy-saving transformation must meet three requirements of energy efficiency,economy and indoor environment comfort.Under the conditions that the main structure of building's exterior wall and roof is 300 mm concrete solid block,100 mm reinforced concrete structure repectively,the best scheme of comprehensive energy-saving transformation consists of 20 mm thick XPS insulation material of southern external wall,50 mm thick XPS insulation material of northern external wall and roof.After the transformation,the building's interior natural light has basically unchanged,and indoor thermal comfort has improved in winter.Relative to the initial building,building heating's energy saving rate of the optimal program is 96.4%,and it is 24.3% compared to the established No.0 program.In addition,the total cost savings is 54,85.4 yuan,compared with the No.0 program.In summary,this study on the transformation's programs,reflects energy-saving design's development space of new residential buildings in Lhasa area,but also it provides idea and basis of energy conservation reconstruction research for old buildings of relatively poor energy-savings.