Evaluation Method Of Green Retrofitting Scheme Of Existing Buildings And Its Application In Office Buildings

There are a large number of existing buildings in China,and most of them are high energy-consuming buildings,resulting in a series of problems,such as energy waste,environmental pollution and so on.With the improvement of energy-saving awareness in the current society and people’s strong desire for a healthy and comfortable environment,people are no longer satisfied with the ordinary energy-saving transformation of buildings.Therefore,the green transformation of existing buildings has become very important,it can not only significantly reduce the energy consumption of buildings,save people’s heating and air-conditioning costs,but also improve our living environment and improve the function of buildings.it is also of great help to enhance the appearance of the city.However,there are often a variety of transformation schemes for the green transformation of a building,and how to select the best scheme from these schemes is lack of theoretical basis in the current design and transformation.Based on this,this paper first takes an existing office building in Tianjin as the research object,takes the evaluation of the green transformation scheme as the starting point,consults the references at home and abroad,and conducts on-the-spot investigation,combined with the current technical level and development characteristics of domestic green transformation projects,as well as the contents of relevant norms and standards such as"Green Building Evaluation Standard"and"Green Reconstruction Evaluation Standard of existing buildings",The evaluation index system of green renovation scheme of existing buildings is established,including4 first-level indicators and 12 second-level indicators.The weight of each evaluation index is determined by the optimal combination of subjective weighting method（AHP+Delphi method）and objective weighting method（entropy method）.Secondly,based on the grey relational evaluation method,a multi-attribute comprehensive evaluation model is established to comprehensively evaluate the optional transformation scheme,and the transformation scheme based on different attributes and optimal comprehensive performance is obtained.Then the fuzzy comprehensive evaluation method is used to compare and verify,and it is found that the calculation results of the two evaluation methods are consistent,which proves that the evaluation index system of the green transformation scheme and the evaluation model of grey relational analysis theory are scientific and reasonable.Finally,in order to verify the transformation effect of the selected scheme,the completed buildings are simulated,tested and investigated from three aspects:building performance,energy consumption and comfort.In terms of building performance,the heat transfer coefficient of the exterior wall after the transformation is 0.464W/（m²·K）,reduced by 71.9%compared with that before the transformation;the concentration of the main indoor pollutants PM2.5,O₃ and TVOC all meet the standard requirements,and the indoor noise value meets the requirements of the code.In terms of energy consumption,the simulation calculation shows that the energy consumption per unit area of the renovated building is 37.9 k Wh/m²,which is 59.4%more energy-saving than that before the transformation.In terms of comfort,indoor temperature,humidity and air velocity meet the comfort conditions.the questionnaire survey found that the satisfaction rate of staff to the comfort of indoor thermal environment was 82.7%.