New solar heat gain requirements introduced in the 2025 National Building Code (NBC) of Canada are changing how windows and glazing systems must be designed and selected, according to a panel discussion at the FGIA Fall Conference.
Moderated by Amy Roberts, FGIA Director of Canadian Codes and Advocacy, the session brought together Jeff Baker of WESTLab Canada, Lisa Bergeron of JELD-WEN and Paul Bush of Vitro Architectural Glass to examine the practical impact of the updated requirements.
Baker explained that the 2025 NBC now provides three compliance pathways: a performance path based on whole-building energy performance; a prescriptive path using points to meet NBC Tiers 1–5 according to climate zone; and a new prescriptive path specifying compliant components by climate zone. SHGC limits apply to both prescriptive approaches.
The changes are intended in part to address overheating in highly efficient building envelopes, creating new considerations for glazing manufacturers and builders. 
Bush highlighted the relationship between SHGC, U-factor and Energy Rating (ER). Coating position can influence solar heat gain and ER, while adding a third lite through triple insulating glass units (IGUs) can reduce U-factor.
Bergeron added that improving U-factor involves balancing glass and frame performance, with lower frame profiles and larger glass areas offering another route to improved thermal efficiency and occupant comfort.
Source: FGIA with additional information added by Glass Balkan
