Regulatory Gap in Fenestration Thermal Performance: Integrating Linear Thermal Transmittance into Energy Codes in Cooling-Dominated Climates

Fenestration systems play a critical role in building thermal performance, particularly in cooling-dominated climates where envelope inefficiencies directly amplify electricity demand. In Saudi Arabia and other Gulf Cooperation Council (GCC) countries, cooling accounts for the majority of building energy consumption. Nevertheless, the façade and insulated glass industries are experiencing rapid market expansion. Despite this technological evolution, prevailing regulatory frameworks, including the Saudi Building Code (SBC), ASHRAE 90.1, and the International Energy Conservation Code (IECC), primarily rely on area-weighted U-values and solar heat gain coefficients (SHGC), without explicitly integrating multidimensional thermal bridge effects such as linear thermal transmittance (ψ). This paper investigates the structural omission of ψ within current energy compliance systems, evaluates its implications in cooling-dominated climates, and proposes a phased regulatory integration pathway aligned with sustainability objectives under Vision 2030. Literature synthesis indicates that thermal bridges may increase cooling loads by up to 25% and total building energy use by 5–30%, while remaining structurally omitted from compliance metrics. The findings highlight the need to transition from simplified prescriptive compliance toward physics-informed governance capable of addressing evolving façade complexity in hot-arid environments. The proposed framework offers a systematic pathway for integrating linear thermal transmittance requirements while supporting regional sustainability goals and the advancement of high-performance building technologies.