Regulatory Gap in Fenestration Thermal Performance: Integrating Linear Thermal Transmittance into Energy Codes

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 facade and insulated glass industries are experiencing rapid market expansion. Despite this technological evolution, prevailing regulatory frameworks, including the Saudi Building Code Energy Conservation Requirements (SBC 601), ASHRAE 90.1, and the International Energy Conservation Code (IECC), primarily rely on area-weighted U -values and solar heat gain coefficients (SHGCs) without explicitly integrating multidimensional thermal bridge effects such as linear thermal transmittance ( ψ ). This paper examines the omission of ψ from 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 reports indicate that thermal bridges may increase cooling loads by up to 25% and total building energy use by 5–30%, depending on climate severity and façade configuration. The findings highlight the need to transition from simplified prescriptive compliance toward a physics-informed governance capable of addressing evolving facade complexity in hot-arid environments. The proposed framework offers a systematic pathway for integrating linear thermal transmittance requirements while supporting regional sustainability goals and advancing high-performance building technologies.