Towards the goal of zero-carbon building retrofitting with variant application degrees of low-carbon technologies: Mitigation potential and cost-benefit analysis for a kindergarten in Beijing

China's building industry urgently needs to accelerate the deployment of zero-carbon building technologies and zero-carbon project practices to facilitate the net-zero target. This study aims to explore the application potential and benefits of applying low-carbon technologies in existing buildings from a life-cycle perspective to drive zero-carbon building retrofits in China. To illustrate the impacts of the application of low-carbon technologies on zero-carbon building retrofitting, the mitigation values and abatement costs were evaluated for 16 typical low-carbon technologies of buildings, and the comprehensive incremental benefits model considering the environmental, economic and social impacts was developed. The incremental cost-effectiveness ratio index with the time value was proposed to explain the feasibility of building zero-carbon retrofit for different levels of technology application. In this study, a public building (kindergarten) in Beijing was taken as a study case, and the initial life-cycle energy consumption and carbon emissions based energy simulation were considered as the benchmark to compare the effect of zero-carbon transformation of the case building with different degrees of technology application. It is found that the economic benefit of implementing zero-carbon retrofitting of the case building through these low-carbon technologies increases from 42% to 66%, while the environmental benefit decreases from 57% to 32%. The analysis of incremental cost-effectiveness ratio indicates that achieving zero-carbon renovation over the lifetime of the kindergarten is economically feasible, and the comprehensive incremental benefits of the application of low-carbon technologies will exceed the incremental cost. The quantitative research for building low-carbon technologies in this study might provide an effective assistance on technology selection at the project level for better zero-carbon renovation strategies.