Passive thermal performance of vernacular dwellings in the hot summer and cold winter region of Southern Henan, China

Traditional vernacular houses can enhance indoor thermal comfort and sustainability through passive design. This study analyzes a representative courtyard dwelling in southern Henan, China, in a hot-summer, cold-winter climate using field measurements and a calibrated EnergyPlus model. The influence of orientation, window-to-wall ratio, attic configuration, envelope insulation, and floor materials is assessed with a regional comfort standard and seasonal comfort ratios. Enhancing wall insulation substantially improves summer comfort and increases the winter comfort ratio to 22.1%, while high thermal-mass floors help reduce indoor temperature swings. A ventilated attic further provides a modest improvement in summer comfort and indoor thermal stability. In winter, increasing the window-to-wall ratio extends comfort time from 0.8% to 10.9% through passive solar gains but also increases the risk of overheating in summer. A coordinated heritage-compatible passive retrofit that combines adobe walls, a timber roof, an optimized attic space, low-E glazing, and high-thermal-mass floors improves comfort in both seasons and reduces simulated annual heating and cooling energy use from 1640.0 kWh to 1395.5 kWh. The results provide quantitative guidance for prioritizing passive retrofit measures in traditional houses in hot-summer, cold-winter regions.