Cold region, hot risks: heatwave exposure and coupled thermal-humid vulnerability of rural elderly dwellings under future climate scenarios

Under global warming, heatwave risks in severe cold regions have increased substantially. Assessing heatwave risks in rural elderly housing and protecting the thermal health of older adults have become increasingly important. Existing heatwave assessment studies predominantly employ static thresholds and often fail to adequately account for building thermal-humid coupling effects. Focusing on rural dwellings and elderly populations in the severe cold regions of China, this study established a correspondence framework between Shared Socioeconomic Pathway (SSP) and Representative Concentration Pathway (RCP) scenarios to link future heatwave-risk analysis with building thermal-humid vulnerability evaluation. A dynamic-threshold-based heatwave risk assessment framework and a thermal-humid vulnerability index (T-HVI) model were further developed to characterize the evolution of heatwave risk and thermal-humid vulnerability under multiple climate scenarios. Results indicate that the SSP5–8.5 scenario presents the most severe heatwave risk, with extreme events characterized by cumulative heat of heatwave events (HWC) values exceeding 80 °C and maximum duration of heatwave events (HWD) surpassing 16 days. Both the thermal-humid vulnerability of rural dwellings and the severity of indoor thermal–humid stress conditions experienced by older adults increase with rising carbon emission intensity. The 75th percentile values of T-HVI are 0.276, 0.342, and 0.571 under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Heatwave risk and rural dwelling vulnerability exhibit partially asynchronous variation patterns, suggesting that the temperature indicator alone is insufficient to fully characterize rural dwelling vulnerability. The findings support climate-adaptive retrofitting of rural dwellings and improved thermal health protection for older adults in severe cold regions.