Low-carbon renovation of old residential blocks: An envelope-focused assessment framework for carbon reduction effects and economic benefits

Abstract

Retrofitting building envelopes in the era of existing stock is an effective pathway to achieving carbon neutrality goals, requiring a comprehensive consideration of carbon reduction benefits and economic benefits. However, existing research focuses on the individual buildings and has not yet established a comprehensive assessment method at the block scale. This study aims to propose a multi-objective framework to assess the operational carbon reduction and economic benefits of retrofitting building envelopes in old residential blocks. First, this study employs architectural typology and cluster method to categorize 102 real cases of old residential blocks in Wuhan into three fundamental categories along with twelve derived variants. Second, under both single-component and multi-component retrofit scenarios, 2472 renovation schemes are generated. Then, sensitivity and variance analyses within the framework identify the key retrofit components and elements under each objective. Finally, the optimal renovation scheme sets for 3 types of old residential blocks are obtained, and the multi-level technical lists of envelope components-renovation materials-thermal parameters are formed. The proposed scheme sets and multi-level technical lists demonstrated good robustness after undergoing uncertainty analysis and comprehensive verification. The results indicated that multi-component retrofits enhance the carbon reduction effect by 9.25 to 23.95%, compared to single-component approaches. The heat transfer coefficient of external walls primarily affects the carbon reduction effects, while the heat transfer coefficient of external windows and the solar heat gain coefficient primarily affect economic benefits. In terms of comprehensive benefits, the heat transfer coefficient of exterior windows and that of exterior walls collectively serve as decisive factors. The technical framework proposed in this study enables policymakers and practitioners to rapidly assess the effectiveness of schemes and identify renovation priorities in the early stage of renovation. It provides a scalable technical pathway for decarbonizing old residential blocks worldwide, thereby supporting energy efficiency, emissions cuts, and sustainability within the building sector.