Energy Efficiency Retrofit for Existing Residential Buildings in China’s HSCW Zone in Multiple Scenarios: Energy Economic Analysis

Retrofitting existing residential buildings in China’s hot summer and cold winter (HSCW) zones significantly improves building energy efficiency. Current studies on retrofitting existing residential buildings mostly concentrate on single scenarios, primarily in the northern region. However, there is a need for better decision-making information for multiscenario retrofits in these areas. This study introduces a retrofit support model for designing and evaluating multiscenario energy efficiency retrofits. It proposes three retrofit scenarios (minor, medium, and major) based on typical residential buildings in the region. Using DesignBuilder (version 6.1) software, simulation models were created, and sensitivity analysis was conducted to identify critical factors. An energy-economic assessment methodology then determined the best combination of scenarios. The results indicated that the optimal scenarios for the minor and moderate retrofit scenarios achieved optimal levels of energy saving (43.17% and 49.13%, respectively) and net present value (RMB 49,048.7 and 56,401.44, respectively). The major retrofit scenario achieved a 53.38% energy saving and an economically optimal net present value of RMB 56,423.91. Energy savings did not always correlate positively with initial investment costs due to the dominant role of the facade factor in economic aspects. This study helps improve building energy efficiency and offers policymakers a way to evaluate different retrofit options.