Research On Thermal Performance Of Residential Building Envelopes In The Yangtze River Basin

The Yangtze River Basin plays an extremely important role in China's economic and social development.Nearly one-third of the country's population reside in this region,developing complete urban systems,numerous residential buildings,large industrial scales,developed economic entities and a regional GDP exceeding 40% of the country's total value.Meanwhile,the Yangtze River Basin is a vast land with special climate characteristics,cold and gloomy in winter,hot and stuffy in summer,with high humidity throughout the year and distinctive climates in the upper,middle and lower reaches.The harsh thermal and humid environment of residential buildings prohibits rigid uniformity in improving the thermal comforts of residential buildings and analyzing the impact of climate on building energy consumption.As most cities of the region are non-centralized heating areas,its long-term energy consumption patterns of residential buildings are quite different from that of severe-cold and cold regions,which bears the energy-using characteristics of "specific time,specific room".However,the simulated energy use conditions stipulated in the current energy saving design standards for residential buildings in China are inconsistent with the actual energy use conditions in this region,which leads to the gap between the energy saving efficiency obtained according to the existing design methods and the actual energy saving effects,and makes it impossible to evaluate the energy saving effect of buildings in this region practically and accurately.Based on the above background,the author constructs architecture climate zoning by considering both climatic characteristics and architectures of the Yangtze River Basin and studies the thermal performances of envelop structures suitable for different zoning based on the current energy-saving design standards while combining the energy-using regional characteristics of "specific time,specific room",aiming to improve and enhance the indoor thermal environment levels of Yangtze River Basin and reduce the energy consumption of heating and air conditioningTo implement a more targeted analysis of the energy-using behaviors and the envelope improvement requirements in different cities in the Yangtze River Basin,this paper first analyzes the climate characteristics of the region.After analyzing data of the typical meteorological years of 55 cities,the heating degree days (HDD18),cooling degree days(CDD26),and annual outdoor average wind speed were selected as the three meteorological indicators to comprehensively reflect the regional climate characteristics.Next,based on the cluster analysis of characteristic parameters,the Yangtze River Basin is divided into four architectural climate zonings:Zone ?-Zone ?.This method overcomes the limitation of single index of the original zoning methods and the deficiency of the artificially-determined boundaries,and increases the objectivity,accuracy and scientificity of the zoning results.At the same time,it also provides basis of classification for constructing a building energy-saving technical system suitable for different areas of the Yangtze River BasinSubsequently,Shanghai,Changsha,Chengdu,and Garze were selected as representatives for the Yangtze River Basin's architecture climate zoning:Zone ?-?.DesignBuilder software with EnergyPlus as core was used to construct the residential building reference model for year-round dynamic simulations.Compared with the existing standard full-time energy consumption simulation,the paper studies the influence of changing the heat transfer coefficient of the external walls,internal partition walls,floors,and roofs on energy consumption of heating and air conditioning in different climate zonings.The results show that the energy consumption of"specific time,specific room" can significantly reduce the energy consumption per unit area of heating and air-conditioning compared with the full-time energy consumption,decreasing by 10% to 30%.Under both modes,the energy saving effect of reducing the heat transfer coefficient of the envelop structure on the energy consumption of heating and air conditioning per unit area of residential buildings works best in the external wall,followed by the roof and the internal partition wall,and the worst in the floor.In the climate zone ??? of the Yangtze River Basin,using "specific time,specific room" energy-using mode,the energy saving efficiency of reducing the heat transfer coefficient of the external wall is lower than that of the full-time energy-using mode,and the energy saving efficiency of reducing the heat transfer coefficient of the roof,internal partition wall and floor is higher than that of the full-time energy-using mode.In conclusion,this paper puts forward optimization suggestions on thermal parameters limits,energy consumption season and energy consumption time of envelopes on the basis the energy-using characteristics of "specific time,specific room" and thermal comfort requirements in the Yangtze River Basin,and clarifies the optimization direction of thermal performance of envelopes for reducing energy consumption of heating and air conditioning in the region.