Metamodel-assisted global sensitivity analysis of thermophysical design priorities for vernacular dwellings in southern Henan under current and future climates: A pathway–response interpretation framework

Under climate warming, improving the thermal performance of free-running buildings is important in seasonally contrasting regions. This study identifies and physically interprets thermophysical design priorities for two selected vernacular dwelling prototype cases in southern Henan, China—a Huizhou-style and an earthen-block dwelling—under fixed free-running conditions, using winter–summer cumulative operative temperature discomfort degree-hours (OTDDH). Field survey, on-site measurements, EnergyPlus simulation, NSGA-II-optimized XGBoost metamodeling, and Sobol global sensitivity analysis were combined to evaluate eight climate-responsive variables under the baseline climate and four EC-Earth3 projections (SSP2-4.5 and SSP5-8.5 for 2050 and 2080). The metamodels achieved R 2 > 0.94, CV(RMSE) < 1%, and NMBE within ±0.1%. Within the prescribed variable ranges, external-wall thermal inertia and thermal resistance ranked first and second under the baseline climate, with total-order Sobol indices ( S Tᵢ ) of 0.41 and 0.32 for the Huizhou-style prototype and 0.76 and 0.17 for the earthen-block prototype. Across future scenarios, these variables remained first and second, respectively. Warming shifted discomfort from winter dominance toward a more balanced winter–summer burden and reorganized secondary priorities, particularly orientation and south-facing window-to-wall ratio (WWR). Notably, despite different form–envelope configurations, the prototypes’ baseline cumulative OTDDH differed by only 6.70% under the adopted metric, showing that diverse designs can yield comparable free-running outcomes at case level without implying typology-level thermal equivalence. The proposed pathway–response framework provides a physically traceable basis for interpreting Sobol rankings by linking ranked variables to heat-balance pathways and endpoint response strength.