A simulation-based assessment of future heatwave impacts on building energy demand and outdoor thermal comfort in hot-humid cities.

With the increasing frequency of extreme heatwave events driven by climate change, urban residential areas in hot-humid regions are facing severe thermal environmental and energy challenges. To comprehensively assess heat risks and building performance under future extreme heatwave scenarios, this study developed localized future extreme heatwave conditions for the Guangzhou region using downscaled climate data from four Shared Socioeconomic Pathways (SSP) scenarios. By integrating field measurements, ENVI-met and Energyplus simulations, the study systematically analyzed the outdoor thermal environments and building performance across five typologically diverse residential areas (LCZ 1-3). The results indicate that: (1) Future extreme heatwaves will drastically elevate outdoor heat stress, with the most severe scenario (SSP5-8.5) increasing the peak Physiological Equivalent Temperature (PET) by over 11 °C and expanding the spatial extent of strong heat stress areas to cover over 95% of sites with low green cover; (2) Indoor thermal environments will deteriorate significantly, with peak indoor temperatures exceeding 36.7 °C and early morning temperatures already above 32 °C, indicating insufficient nighttime cooling and heightened heat health risks; (3) Building cooling energy demand is projected to surge, with daily total consumption increasing by 6.1-8.5% (SSP1-2.6), 26.0-26.8% (SSP2-4.5), and 10.9-14.7% (SSP3-7.0) by the end of the century. The findings reveal the distinct thermal vulnerability of different urban forms and underscore the urgent need for differentiated, context-specific heat mitigation strategies to enhance urban resilience.