BIM-based Life Cycle Environmental Impact Assessment Of The Building Retrofit Project

In the past few decades,China have witnessed fast urbanization,and at the same time,mountainous resources and energies have been consumed by the building sector,which has caused great pressure to the environment.Now governments of each level have reached a consensus that the building sector should adopt measures to guarantee the sustainable development.Life Cycle Assessment(LCA)is an ideal method to quantify the potential environmental impact during a product's life cycle in a comprehensive way.However,for the building,due to its irregular and complicated construction process and multiple scenarios of operation,refurbishment,demolition and waste disposal options,it is a giant challenge to implement LCA in the building sector.Recently,Building Information Modeling(BIM)has been widely adopted in China's construction practice and it is thought to be an effective tool to manage and store the life-cycle data of a specific building.Therefore,some studies have focused on its implementation in LCA of buildings.However,the number of similar studies is still small,and quite few of them have fully applied BIM to acquire the data required for LCA.In addition,extremely few papers have studies the BIM application in retrofit buildings' LCA,which will certainly become the main trend in China's building industry.This study aims to propose a BIM-based method for the LCA of building retrofit project so that the key factors or processes that contribute very much to the total environmental impact during the life cycle of the building retrofit project can be identified.This will provide the professionals with real time feedback for them to optimize their designs and construction plans.Firstly,this study reviews many previous studies on the BIM-LCA topic and thus analyzes the barriers for the BIM application in LCA,which lays a foundation for the following study.Secondly,a method of BIM-based retrofit project LCA is built.Also,the data required by it and the value of BIM application in acquiring these data are analyzed.Thirdly,with the consideration of the practice of China's construction sector,the methods of using BIM to collect the required data,such as constrction,operation and end disposal,have been developed.Lastly,to demonstrate the proposed method,an office building is selected as a case study.BIM tools and LCA tools are combined together to assess the potential life-cycle environmental impact of the office building.A local LCA tool of China,eFootprint,is employed to create the LCA model and the life cycle database of China(CLCD)is used as the main data source to calculate the environmental impact.However,because of lacking some data on construction materials,ELCD and ecoinvent are used as supplementary.The results are analyzed by comparing the impacts of various processes and building materials.Additionally,the relationship between component quantity and cost is analyzed.The proposed framework and methods prove to be a valuable for reducing the time spent on data collection and processing.BIM application can improve the accuracy and reliability of the LCA results,which makes the professionals in the building industry make better decisions on retrofit plan selection and finally realize green buildings.