Decision Boundary of the Superposition Effect of Low-Carbon Retrofit Measures for Office Buildings in the Hot Summer and Cold Winter Region: The Asymmetry Between Carbon Emissions and Thermal Comfort

Multi-measure building retrofits often estimate combined performance by linearly superposing single-measure effects, but the superposition error may change the compliance judgment on carbon-reduction and thermal-comfort targets, and verifiable quantitative evidence on the conditions under which linear superposition is suitable for scheme screening remains lacking. Using a Chongqing-localized DOE Medium Office model, this study constructs a "superposition error–prediction margin–decision reversal " analysis framework. Scheme-level superposition errors are quantified from the single-measure and combined results of the EnergyPlus model; the 95% empirical envelope of the overprediction error in carbon reduction is determined using 60 calibration samples; and, after the screening rule is fixed, its application is evaluated using 300 additional candidate schemes. The results show that, under the targets and sample conditions of this study, a predicted carbon-reduction margin exceeding this error envelope (2.567 kgCO2/m²) can serve as a screening condition for accepting the compliance judgment of the linear prediction. Among the newly added candidate solutions, 46 schemes satisfy this condition, and their combined results from the EnergyPlus model all meet the carbon-reduction target; the thermal-comfort metric forms no screening interval satisfying the acceptance condition under any of the eight evaluation definitions, indicating a difference in the first-pass screening utility of the two types of metrics. Hourly decomposition further shows that threshold mapping is an important source of the mean superposition deviation of the thermal-comfort metric. This study provides quantitative evidence for target-oriented first-pass screening of combined schemes using existing single-measure evaluation results, and the proposed framework can be applied to office buildings in similar climate zones after recalibration and verification.