Study On Thermal Performance And Optimization Design Of Raw Soil By Cliff-side Cave Dwellings

With the acceleration of urbanization,the urban area is increasing.Meanwhile,with the development of modern science and technology,people's requirements for the comfort of living space are gradually increasing,and people pursuit the indoor thermal comfort environment through manual adjustment too much,resulting in huge energy consumption.It can be seen that low-carbon development in the construction sector is an important way to strengthen the construction of ecological civilization and achieve sustainable development.Therefore,how to improve the indoor environment comfort and effectively control the building energy consumption has become an urgent task in the research of urban and rural construction,and needs to be solved urgently.The earth-sheltered dwelling,as one of the traditional residence,which is made up of local building materials,is green and environmentally friendly,and is a typical climate-adapted building.At the same time,the loess relies on the characteristics of high heat capacity of loess materials can realize the functions of thermal insulation,heat storage and regulation of indoor thermal and humidity environment.Excavating the ecological experience contained in the earth-sheltered dwelling to guide modern sustainable building practices is instructive.However,previous research on the thermal performance of the earth-sheltered dwelling is mostly focused on qualitative research,and the quantitative research is still relatively rare;and the research on regeneration design is rarely reported.Therefore,it is very significant to excavate the thermal performance characteristics of the cliff-side cave dwelling fully and establish an evaluation system for the regenerative design of the cliff-side cave dwelling.In summary,this paper takes cliff-side cave dwelling as the research object and has carried out the following work based on the National Natural Science Foundation project “Thermal Responsive Characteristics and Regenerative Design Evaluation of Raw Soil Construction in Western Henan”(Project No.51608486):(1)The field monitoring of a typical four-hole cliff-side cave dwelling in GongYi city in the winter and summer was carried to analyze its thermal and humidity environment characteristics under the extreme weather conditions.It shows the air temperature and air relative humidity in winter basically meet the comfort requirements.However,the air relative humidity is high in summer,with an average of 65.2%.(2)The brick building adjacent to the Yaodong was selected to compare with the Yaodong.The comparative analysis shows that the thermal and humidity environment of the cliff-side cave dwelling is better than the brick building.The average indoor temperature of cliff-side cave dwelling is 4.5 °C lower in summer and 9.6 °C higher in winter than that of brick building;the indoor air relative humidity of Yaodong ranges from 36.3% to 58.5% in winter,and that in brick building increases from 45.3% to 67.8%.Both can maintain a relatively stable state.(3)The analysis of the inner wall surface temperature,heat flux density and thermal performance index of the building envelope shows that the south wall is the main part of heat gain in summer and heat loss in winter.Except for the south wall of the cliff-side cave dwelling,the thermal performance indexes of the building envelope are far greater than those of the brick building.Therefore,the south wall is the weak point of thermal insulation of the Yaodong.The heavy envelope enclosure is the main reason for the warm in winter and cool in summer of Yaodong.(4)An analysis model of the cliff-side cave dwelling and its annual thermal and humidity environment was simulated by EnergyPlus.The analysis shows that the annual air temperature of Yaodong fluctuates from 6.0 to 29.4°C.The air relative humidity increases from 37.5% to 88.5% with an average of 66.7%,which is high for the poor indoor ventilation quality of the cliff kiln.It also shows that 30.76% of the time is in the I-level comfort zone,mainly concentrated in the spring and early summe.(5)Combined with the characteristics of thermal performance of the cliff-side cave dwelling,the measures of adding insulation layer and insulation layer were put forward to solve the problems of high indoor air relative humidity and high heat loss in winter.The analysis shows that the insulation layer can effectively reduce indoor air temperature fluctuation and the proportion of low temperature and high temperature.Setting humidity control layer can effectively reduce the indoor air relative humidity and maintain the humidity within the comfort rage to improve the indoor comfort level.(6)Based on the indoor and outdoor thermal environment,energy saving,water saving,material saving,economy and other conditions of the cliff-side cave dwelling,the evaluation system of the Yaodong's regeneration design was proposed.And the different regeneration design schemes of the cliff-side cave dwelling were evaluated by it.The analysis shows that the original model's evaluation grade is C,which can adapt to the local environment better,but its indoor thermal environment needs further improvement;when the thickness of the insulation layer of the south wall is 0.04 m,the overall evaluation by the cliff-side cave dwelling is better than other thicknesses.When the thickness of the composite phase change humidity control layer in the building envelope is 0.02 m,the evaluation grade is higher than others',which is Grade B.