Climate Change Threatens Traditional Yemeni Architecture: Building Energy Simulation of Thermal Performance in Old Sana’a Tower Houses Under Mid-Century Warming Scenarios

Climate change poses severe threats to cultural heritage, yet thermal performance impacts on traditional architecture in conflict-affected regions remain poorly quantified. This study provides one of the first comprehensive assessments of climate change effects on UNESCO World Heritage architecture in Yemen’s Old City of Sana’a. We employed building energy simulation (DesignBuilder/EnergyPlus) to evaluate the thermal performance of a representative five-story traditional adobe tower house under three climate scenarios: baseline (1974–2017), SSP2-4.5 (moderate emissions, 2041–2060), and SSP5-8.5 (high emissions, 2041–2060). Climate projections were derived from five CMIP6 models using the morphing methodology, with natural ventilation-only operation (no mechanical cooling). The results demonstrate dramatic thermal performance degradation: annual overheating hours (>30 °C) increase more than 10-fold from 111 h (baseline) to 1264 h (SSP2-4.5) on the most vulnerable floor, representing escalation from 1.3% to 14.4% of the year. Extreme heat exposure (>32 °C) emerges under climate scenarios (324–423 h annually) and is absent under baseline conditions. Thermal comfort declines 27–30 percentage points across all floors. The findings reveal the systematic failure of passive cooling mechanisms under elevated temperatures, particularly when nighttime temperatures exceed 20 °C, eliminating nocturnal heat purging opportunities. The results necessitate the urgent development of heritage-sensitive adaptation strategies for Old Sana’a and similar UNESCO sites in arid regions facing compound climate-conflict vulnerability.