The Optimization Of The Insulation And Heat Storage Of Rural Residential Building Envelope In Lhasa Region

Energy resource and environment are the great problems that every country is faced with.In recent years,the urban construction is developing rapidly in Tibet,and the energy demand is increasing.Lacking of conventional energy sources and fragile ecological environment in Tibet,but it is rich in solar energy resources in China and even the world.It has important significance of energy efficiency and environment protection to study how to utilize the solar energy in residential building for the low-energy efficient target.Though the field study in winter,it is found that there is not central heating in Lhasa,the indoor thermal environment is generally poor in rural residential buildings because of the poor thermal performance of the building envelope.Because of the lack of the scientific and technical guidance,the indoor thermal environment cannot be promoted and even worse in the rapid process of the traditional residential building renewal.The experiment and theory of thermal transfer process has proved that the thermal transfer of building envelopes is affected by solar radiation.According to the analysis of sol-air temperature,Effective Overall Heat Transfer Coefficient(EOHTC)of building envelope is introduced,and the threshold of EOHTC in various orientations are calculated respectively,namely the roof,the south wall,the eastern and western wall and the north wall are 0.79 W/(m2·K),1.16 W/(m2·K),0.92 W/(m2·K)and 0.85 W/(m2·K).The parameter of thermal performance of the exterior windows and the window-wall ratio(WWR)in different directions in Lhasa are analysed using Design Builder simulation software.It is concluded that the range of WWR in different directions aiming to promote thermal environment during night.It is advised that WWR of south-faced wall should be much larger,and the size of window in north-faced wall should be much smaller for the sake of the basic needs of the daylighting and ventilation.The design of window in east and west walls of north-faced room are recommended rather than south-faced room,and the area of the windows should be limited at 10% of the east or the west wall.Double glazing with low price is recommended in Lhasa.The indoor thermal environment affected by heat storage performances of building envelopes is analysed using simulation software.The construction optimization of building envelope is proposed through the comparison and analysis of different materials and constructions in heat storage performance.It is recommended that thick wall and materials can be used in design of building envelope,which is beneficial to improve thermal environment and result in higher indoor temperature and smaller temperature fluctuation.It is discussed and analysed the insulation and heat storage performance of residential building envelope in rural Lhasa.The thermal parameters and optimization construction of building envelope is proposed aiming to improve the indoor thermal environment,which would contribute theoretical references to the renewal of rural residential building in this region.