Analytical Study On The Impact Of Prefabrication Ratios On Carbon Emissions Of Buildings

Prefabricated buildings have advantages in terms of carbon emission reduction,energy consumption reduction,material saving and waste management.As an important indicator for evaluating assembled buildings,it is important to study the impact of different prefabrication ratios on the carbon emissions of buildings in order to optimize the carbon emissions of prefabricated buildings.In this paper takes prefabrication ratio and carbon emission as the research object,based on the life cycle assessment and BIM technology as a means to study and analyse the change trend of building carbon emission under different prefabrication ratios.The main research elements are as follows:（1）Defined a carbon emission assessment system for prefabricated buildings based on prefabrication ratio.Following the relevant theory of LCA,the life cycle assessment of prefabricated buildings based on prefabrication ratio（RBLCA）was established,defined in four stages:defining the objectives and scope,inventory analysis,impact assessment and interpretation of results,respectively,to construct the assessment framework of RBLCA,which provides a theoretical basis for subsequent research.（2）A carbon emission calculation system for prefabricated buildings is proposed,based on the idea of"component units".Firstly,the carbon emission factors applicable to this study were selected according to the content of the study and the artificial carbon emission factors were modified;secondly,the building entity was divided into prefabricated component units and cast-in-place component units,and the prefabrication ratio and carbon emissions of different component units were calculated and analysed separately;finally,the prefabrition ratios of different combinations of prefabricated components and the carbon emission calculation models of different stages were obtained.（3）Completed the development of a system for calculating and analysing carbon emissions of prefabricated buildings based on prefabrication ratio.The calculation and analysis of prefabricated building carbon emissions based on prefabrication ratio was realised through the secondary development technology of Revit.The definition,general design,functional design and development process of the calculation system were explained and illustrated respectively,and the RBLCA theory and the carbon emission calculation process of each element in each stage were translated through programming,which provided a calculation tool for analysing impact of different prefabrication ratios on the carbon emissions of prefabricated buildings.（4）Instance verification.Taking a prefabricated shear-wall building in Xi’an as an example,the different combinations of prefabricated components were set up using the prefabricated building carbon emission calculation and analysis system based prefabrication ratio to calculate the prafabrication ratios and carbon emissions of different elements at different stages.The results showed that the prefabrication ratio has a significant impact on the carbon emissions of the prefabricated shear wall building;the carbon emission of the prefabricated shear wall building was reduced to a greater extent when laminated panels were applied;the carbon emissions of the prefabricated shear wall building was the lowest when the assembly rate was 61.56%（applying laminated panels,prefabricated external wall panels,prefabricated internal wall panels,prefabricated stairs and prefabricated balcony panels）,which was 11.2 kg CO₂e/m² lower than that of the traditional cast-in-place building.At the same time,the trend of carbon emissions under different elements and the reasons for the change were analysed according to the calculation results.Finally,carbon reduction measures and suggestions were proposed based on the trends of carbon emissions of the three elements.