A Residential Infiltration Performance Index for Saudi Villa and Apartment Archetypes: Cooling-Season Estimates Across 13 Locations

Energy models of Saudi dwellings usually assume one constant air-infiltration rate, and there is no benchmark for judging infiltration in Saudi housing. This study proposes the Residential Infiltration Performance Index (RIPI). It is a logarithmic 0–100 scale of natural, wind- and stack-driven infiltration over the May–September cooling season, with five classes. The index was applied to 1166 simulated villas and apartments at 13 weather locations. A physics-based model was used, with leakage inputs adjusted to airtightness tests of two Saudi villas and results weighted by the 2022 census. Under the baseline assumptions, the median infiltration was 0.19 air changes per hour for villas and 0.06 for apartments. Villas infiltrated about three times as much because more of their envelope is exposed to outdoor air. Rates followed outdoor temperature in sheltered settings and wind speed in exposed ones. Natural infiltration supplied one-fifth to one-quarter of the constant 0.8–1.0 air changes per hour assumed in energy models for villas, and less than one-tenth for apartments. The remainder must therefore be represented as ventilation. The index provides model-based, type- and location-specific inputs for energy models and a fixed scale for comparing dwellings and airtightness requirements.