Impact of Projected Climate Change on the Thermal Performance and Comfort of Residential Buildings in Riyadh, Saudi Arabia: Dynamic Simulation to 2070 and the Effectiveness of Envelope Improvement

The building sector is both a major contributor to climate change and one of the most exposed to its impacts, and dwellings designed today will operate under mid-century climates. This study quantifies the projected impact of climate change on the climate of Riyadh, Saudi Arabia, and on the thermal performance and comfort of a government-approved residential villa archetype, and tests envelope improvement as an adaptation measure. Future hourly weather files for 2061–2080 were generated from a baseline IWEC typical meteorological year by morphing with change factors from the CMIP5 ensemble (IPCC Fifth Assessment Report) under RCP 4.5, at the 10th, 50th, and 90th percentiles of the ensemble warming distribution. Relative to the baseline, summer means rise by 2.1–4.1 °C across this range, days with maxima of 45 °C or more increase from 5 to 40–74, tropical nights above 30 °C from 25 to 72–124, and cooling degree-days by 17–35%. Under the warm-end (90th percentile) file used for the IES Virtual Environment building simulations, living-room PPD rises from about 11% to 13% with wider cooling peaks, and raising wall and roof insulation to ASHRAE 90.1-2019 levels cuts envelope conduction gains by about 6% and energy use intensity from 128.42 to 123.45 kWh/m2·year (−3.9%). The findings support tightening envelope requirements in the Saudi Building Code and integrating future weather files into design practice.