Environmental impact assessment of building envelope insulation standards for decarbonization efforts in a developing country: a case study for Türkiye

Aligned with global decarbonization goals, the building sector is a key focus due to its large share of energy use and emissions. Improving building envelope performance is central to passive design and emission reduction. While developed countries advanced building envelope standards, progress in developing economies has been slower. In this context, Türkiye revised its insulation regulation, TS 825, to better align with decarbonization targets. The updated TS 825:2024, enforced April 1, 2025, redefined climatic zones and introduced stricter U-value limits. However, its environmental and economic impacts have not yet been systematically assessed against national targets. This study offers the first systematic comparison of the 2024 and 2013 editions, quantitatively demonstrating their implications for operational and embodied carbon and costs, and contributing to both scientific literature and policy development. Using a reference residential building across climate zones, the study estimates operational carbon through energy simulations, calculates embodied carbon with life cycle assessment, and evaluates energy and construction costs for economic feasibility. Results indicate that TS 825:2024 reduces operational carbon (1.5-5 %) but raises embodied carbon (1.2-2 %) due to higher insulation demands. In cold, very cold, and severe cold regions, carbon payback periods are 8.5, 8.9, and 5.9 years, with investment payback periods of 22.3, 23.1, and 16.3 years. In contrast, hot zones show carbon payback periods of 11.8–17.4 years and investment paybacks up to 45.4 years. While the revised standard achieves better performance in cold climates, its limited impact in warmer zones highlights the need for region-specific measures to improve cost-effectiveness and emission outcomes.