The role of total solar energy transmittance for normal incidence of the glazed system in climate change adaptation under Italy energy efficiency policies

•Italian energy efficiency policies in buildings should tackle climate change.•Low ggl,n are acceptable in buildings compliant with L.D. 192/2005 and M.D. 06/08/2020.•In climate C, low ggl,n has positive impact on all three regulations.•Low ggl,n is compatible with both M.D. 26/06/2015 and M.D. 06/08/2020 (climate D).•ggl,n has no influence in climates E and F. This study investigates the effectiveness of envelope regulations in mitigating climate change impact on building energy demand in different locations and Representative Concentration Pathway (RCP) scenarios. It aims to assess the building thermal performance (EPtot,nd) in compliance with main Italian energy policies (issued in 2005, 2015, 2020). It specifically examines how variations in total solar energy transmittance of glazed systems (ggl,n) impact heat regulation and overall energy efficiency. Results are variable depending on the national climate zone (from A to F) and related standards. Whereas climate zone E does not show significant gains from ggl,n modifications, in zone A reducing ggl,n (from 0.67 to 0.50) enhances resilience in buildings adhering to 2005 regulation (L.D. 192/2005). In climate zone C, ggl,n reduction benefits all standards, while in zone B this adjustment affects buildings following 2020 regulation (M.D. 06/08/2020), particularly under RCP 8.5. In climate zone F, decreasing ggl,n results in higher EPtot,nd, thereby compromising resilience. It is observed that buildings designed in accordance with L.D. 192/2005, compared to other regulations, show a smaller variation of EPtot,nd over time. In particular, moving from 2020 to 2070, climate zone BSh (Koppen climate classification) is the climate zone that sees the largest EPtot,nd increases over the years, while Cfc is the only zone that shows EPtot,nd decreases in all scenarios. For the other zones, a mixed behaviour is observed, with heterogeneous variations and results. Due to climate change, increased insulation in warm areas has contributed to an increase in overall annual consumption. Effective regulatory planning requires a comprehensive future climate assessment to optimize building energy performance.