Analysis Of Heating Energy Consumption For Energy-Efficient Renovation Of Sunshade And Enclosure Structures In Rural Residential Buildings In Cold Regions

As China’s economy develops,the living standards of rural residents are increasing,and their demand for comfortable living environments is also growing.However,rural residential buildings often have poor envelope performance and larger per capita living areas,which pose challenges for improving thermal comfort and reducing energy consumption.This article addresses the characteristics of rural building forms and behavior patterns that differ from those in urban areas,and proposes an economically feasible technical route for energy-saving retrofitting of the envelope structure of rural houses in cold regions.The existing energy efficiency standards for rural residential buildings in China were reviewed,and literature surveys and questionnaire surveys were conducted to investigate the number of floors,envelope structures,and energy use in rural residential buildings in cold regions.The results showed that the envelope performance of existing rural residential buildings is poor,and cooling or energy-saving measures are rarely taken.The per capita living area in rural areas is larger,with 3-4 bedrooms,but only one bedroom is typically heated in winter for the occupants who have heating requirements.This study selected a rural residential building in a cold region as the testing object and analyzed the indoor temperature of the building’s occupied rooms.Without cooling equipment,the maximum temperature at 1.5 m in the room reached 41.2℃in the summer,which was 3.9℃higher than the outdoor temperature.Based on the actual situation of the building,a sunshade net was designed and installed on the roof of the building in the summer.Through testing and comparison,the average temperature of the roof surface decreased by 3.4℃,and the peak temperature decreased by 7.1℃after the installation of the sunshade net,with a temperature reduction of 3.3～3.8℃at different heights inside the building.However,the indoor temperature still remained at a high level.This study utilizes Design Builder simulation software to conduct energy-saving renovation simulations on the building envelope of rural residential buildings in cold regions.Based on the research results,rural residential buildings in Xi’an are classified into three common building forms:single-story flat roof,single-story sloping roof,and two-story flat roof.Heating scenarios are divided into two types:heating for all bedrooms and the living room on the first floor,and heating for one bedroom,resulting in a total of six models.The four building envelope components(outer wall,roof,window,and inner wall)that affect building energy consumption are individually subjected to envelope energy-saving renovation simulations.By using sensitivity analysis methods,the sensitivity rankings of the building envelope components for the six building models are obtained.The results show that when all bedrooms and the living room on the first floor are heated,the sensitivity rankings for each model are roof>outer wall>window(single-story flat roof model),outer wall>roof>window(single-story sloping roof model),and roof>outer wall>window(two-story flat roof model).Among all models,the thermal transmittance of windows has the least impact on heating energy consumption.When only one bedroom is heated,the sensitivity rankings for each model are roof>outer wall>inner wall>window(single-story flat roof model),outer wall>roof>inner wall>window(single-story sloping roof model),and outer wall>inner wall>roof>window(two-story flat roof model).Finally,an orthogonal experimental design method was used to develop energy-saving schemes for building envelopes,and energy simulation results for different energy-saving schemes were obtained.The energy-saving schemes for different building models were analyzed based on energy savings rates of 30%and 50%.Benefit analysis was used to evaluate the energy-saving effectiveness,economic benefits,and environmental benefits.By comparing the different benefit indicators for each of the sixselected building models,the optimal energy-saving schemes were proposed.Taking a single-story flat-roof building model as an example,the optimal energy-saving renovation scheme for heating all bedrooms and the living room on the first floor was found to have a heat transfer coefficient of 0.66 W/(m~2·K)for the outer walls,1.16W/(m~2·K)for the roof,and 2.3 W/(m~2·K)for the windows,resulting in an energy-saving rate of 53%and a renovation cost of 12,425 yuan.For heating only one bedroom,the optimal energy-saving renovation scheme had a heat transfer coefficient of 0.66 W/(m~2·K)for the outer walls,1.85 W/(m~2·K)for the inner walls,1.16 W/(m~2·K)for the roof,and2.3 W/(m~2·K)for the windows,resulting in an energy-saving rate of 53%and a renovation cost of 2,556 yuan.