Prioritizing Energy-Efficient Envelope Retrofit Strategies for Existing Residential Buildings in Severe Cold Regions Through Multi-Dimensional Benefit Evaluation

Energy-efficient retrofit of existing residential buildings is widely recognized as a cost-effective pathway for reducing heating energy demand and carbon emissions in severe cold regions. However, retrofit decision-making in practice is often constrained by the absence of a structured and quantitative approach for evaluating and comparing the comprehensive benefits of alternative envelope retrofit strategies. In Northeast China, where a large stock of existing residential buildings is characterized by long heating seasons and insufficient envelope thermal performance, this limitation frequently leads to suboptimal retrofit prioritization. To address this gap, this study proposes a multi-dimensional decision-support framework for quantifying and prioritizing the benefits of energy-efficient envelope retrofits in existing residential buildings located in severe cold regions. A representative non-energy-efficient residential building constructed in the 1980s in Changchun, Jilin Province, is selected as a case study. Based on a systematic literature review and expert consultation using the Fuzzy Delphi Method, a hierarchical evaluation framework comprising five evaluation dimensions, twenty-four criteria, and one hundred and ten evaluation factors is established. The Analytic Hierarchy Process (AHP) is then applied to derive the relative importance of the evaluation elements and to examine the consistency of expert judgments. The results indicate that improvement of envelope thermal performance and energy and carbon emission benefits are identified as the most critical dimensions influencing retrofit decisions in severe cold regions. At the factor level, thermal conductivity of insulation materials and external wall heat transfer coefficient emerge as the most influential contributors to overall retrofit benefits. All judgment matrices satisfy the consistency requirement (CR < 0.1), confirming the reliability of the weighting results.Overall, the findings demonstrate that the proposed framework enables a quantitative and comparative assessment of retrofit benefits, supporting the prioritization of envelope retrofit strategies that simultaneously enhance thermal performance and maximize energy and carbon reduction outcomes under technical feasibility constraints. The framework provides a transferable decision-support tool for practitioners and policymakers seeking to improve the effectiveness of energy-efficient retrofit planning for existing residential buildings in severe cold climates.