Optimization Method Of Wall Insulation For Residential Buildings In Hot Summer And Cold Winter Zone

At present,in all of the national energy consumption,the building energy consumption accounts for 27.6%,furthermore,as the construction industry is developing rapidly,the percentage will be higher,and in the year of 2020,the number will reach to 35%.Energy consumption has aroused more attention,and especially the building energy consumption,and it has been the key objective in the 13th Five Year Plan.In all of the building energy consumption,the heat loss of enclosure structures accounts for 60%,70%-80%of which is occupied by the wall.So it is high desired to reduce the energy consumption by improving the thermal performance.Normally,in hot summer and cold winter zone,the climate features the high humidity through the year.However,the effect of humidity on the building structures and building consumption did not get the deserved consideration for a long time,as a result,the heat design of buildings did not meet the demand,or the load of air conditioner is inaccurate,what’s worse,insulated walls according to this standard is not available,so it can not reduce the energy consumption radically.In this study,on the premise of such climate,on the basis of latest coupled heat-moist transfer theory,the heat and moisture transfer and insulation optimization of building walls is researched comprehensively and systematically in the special area.Firstly,on the basis of Kunzel theory,the relative humidity and temperature are selected as driving potentials;the dynamic coupled heat-moist model of building walls is developed according to the laws of mass and energy conservation.The simulation software,COMSOL,which is based on the finite element method,is used to solve the coupled heat-moist control equation.The results compared with HAMSTAD project are validated.Based on results of the equation,combined with the economics analysis model,a method is proposed to optimize insulated walls in hot summer and cold winter zone.By using the method,taking the south-facing walls of residential buildings in Changsha as the research object,the effect of insulation locations(external thermal insulation,sandwich thermal insulation,internal thermal insulation)and insulation materials(expanded polystyrene EPS and XPS extruded polystyrene)on thermal and moisture transfer is studied.The results are as following:the insulation location has little impact on the heat gain and loss of walls and the optimum insulation thickness,but has a significant effect on the time lag and decrement factor.The wall of external thermal insulation has the smallest temperature and humidity swing,and thus has the greatest comfort;the brick-insulation interface of sandwich thermal insulation has the possibility to grow mould during winter;the interface close to outdoor environment of three thermal insulation structures has the risky of condensation in winter.Compared to the XPS,the EPS has better thermal performance,but when the same insulation effect is reached,the EPS is more economical.Taking the difference of solar radiation in different wall orientations into consideration,according to the lifecycle total cost analysis,the optimum insulation thickness on various orientations of external walls of the four typical cities(Chengdu,Shanghai,Changsha,Shaoguan)in hot summer and cold winter zone is determined,and the effect of solar radiation on load and economic benefits of orientations is analyzed.The results are as following:in different cities,the heat gain and loss of walls is different;in the same city,the optimum insulation thickness and energy benefits in various orientations is also different.The south-oriented walls present the smallest optimum insulation thickness and the lowest net present,while the situation of the east-oriented and west-oriented walls is opposite.Even in hot summer and cold winter zone,the optimum insulation thickness of the main orientation has little impact on the economic benefits and the total energy consumption of building external walls.To avoid purchasing different insulation materials and the miscellaneous construction organization,the external walls can use the same insulation thickness without considering all orientations in such area.