Evaluation On Economic And Thermal Performance For Residential Envelopes In Hot Summer And Cold Winter Zone

At present, it is estimated that the building sector consume 27% of total national energy, with the increasing of economic and requirement on living standards, the proportion for building energy consumption in China is increasing. It is estimated that the building sector consumption will be 35% of total in the year of 2020, building energy conservation becomes the key objective of energy conservation. Buildings constructed according to Chinese energy efficiency design standard have a large disparity with developed countries, the heat conduction coefficients of external wall, roof and windows are 3~4 times, 2.5~3.5 times and 1.5~2.2 times higher than those of developed countries, and air permeability through window and door is 3~6 times higher, so reducing the energy consumption of building envelop is the key link of building energy conservation.This paper puts forward evaluation of energy and thermal performance (EETP) index for the residential envelopes according to the climate of hot summer and cold winter zone. EETP index is used to judge the energy consumption per building volume and temperature difference between indoor and outdoor,and EETP index regards the whole envelope as a system by judging whether the whole thermal performance meet the standard or not instead of standing on points of each component of building envelope. In order to show the thermal performance of envelopes in different seasons, EETP index is classified into EETPC which is the cooling season index, EETPH which is the heating season index, and EETPY which is the whole year index. Geometrical parameters, thermal parameters and meteorologic parameters are included within EETP expressions. Geometrical parameters of envelope include building volume and areas of wall, roof and window, which can reflect the window to wall ration (WWR), building's shape coefficient; thermal parameters include heat-transfer coefficients of external wall, roof and window, solar radiation absorptance of external wall and roof, shading coefficient of external window; the meteorologic parameters which is gained based on cooling season and heating season include the mean temperature difference between outdoor and indoor, standard solar factor and the equivalent temperature difference of opaque envelope; the meteorologic parameters are on the basis of cooling and heating season, and have been calculated from the results of energy simulation tool eQUEST. The four cities of Shanghai, Changsha, Shaoguan, and Chengdu are selected to represent, A, B, C and D subzone of hot summer and cold winter zone in China, respectively. The regression equations of EETP index with cooling/heating load and energy consumption were built up, including the formulae of EETPC with peak cooling load, accumulative cooling load and energy consumption for cooling, respectively, the formulae of EETPH with peak heating load, accumulative heating load, and energy consumption for heating respectively, and the correlation ship of EETPY with energy consumption both for cooling and heating. In order to validate the veracity of the EETP methodology, peak load, accumulative cooling/heating load, and energy consumptions of two cases selected at random have been calculated in the four cities using EETP method, and DeST and eQUEST simulation software, respectively, Results indicate that the algorithm is reasonable, the results are effective and exact.With the key objective to make EETP an indicator of the impact of the envelop on the energy use in residential buildings, the maximum allowable values of EETP were determined in the four cities when meeting the compulsory indices of"Design standard for energy efficiency of residential buildings in hot summer and cold winter zone"(JGJ134-2001), if the EETP value of some building is lower than maximum allowable value, the building meets the Standard. The corresponding allowable EETPC, EETPH, EETPY when achieving different energy-saving degrees on basis of it were also analyzed, these can be the reverences of residential envelope optimization designs.In order to analyze the effects of influence factors on EETP index and energy consumption, this paper focused on the factors of building's shape coefficient, heat transfer coefficient of wall/roof/window, solar radiation absorptance of wall/roof, shading coefficient of window and WWR, the sensitivity coefficient of each parameter on EETP index and energy consumption were also calculated, the weight coefficients of each parameter of cooling season, heating season and the whole year were gained in the four cities, it has important meanings to carry out energy conservation on building envelope.The economic analysis of envelope is the object of this study, the life cycle economic evaluation of building envelop was proposed based on EETP theory, an economic evaluation model for building energy conservation technology was established. The model is exoteric, all energy conservation design can be described, and uncertain factors are contained. The model can optimize the design of basic building components, including walls/roof, windows and insulation layers. Economic evaluation results can be the guidance for the optimization of projects.Finally, this paper discussed the shortages of energy conservation work in hot summer and cold winter zone, and gave some suggestions from revising energy efficiency standard for residential buildings, improving energy efficiency label and establishing energy consumption statistical system for residential building.