New solar heat gain coefficient (SHGC) restrictions in the National Building Code of Canada are reshaping how Canadian fenestration products are specified, according to a panel at the Fenestration and Glazing Industry Alliance Fall Conference. The session, moderated by FGIA director of Canadian codes and advocacy Amy Roberts, featured experts from WESTLab Canada, JELD-WEN, and Vitro Architectural Glass, Glass Canada reported. Panelists mapped out three compliance paths and detailed how the 2025 code changes affect glass package selection and frame design.
The discussion comes as energy codes tighten and builders face new limits on solar heat gain in highly efficient building envelopes. The changes are intended to address overheating, but they also force manufacturers and specifiers to think more carefully about the relationship between SHGC, U-factor, and Energy Rating. Compliance now requires a more nuanced approach to product selection, with solar control, thermal resistance, and frame performance all influencing whether a building meets code.
Three Paths to Compliance
The 2025 NBC introduced three distinct compliance routes, according to Jeff Baker of WESTLab Canada. “The NBC introduced some new changes in 2025,” Baker said. “There are now three paths to compliance in the code.”
Baker described the paths as follows:
- A performance path in which builders work with an energy advisor and are free to use any fenestration product, provided the whole building meets its performance target;
- A prescriptive path in which you can score points to achieve NBC tiers one through five by using components that are above minimum code in each climate zone;
- A new prescriptive path in which there is a set of prescriptive components that comply by climate zone. In both prescriptive paths, SHGC limits will apply.
The shift marks a significant change for manufacturers who previously relied on a single set of component requirements. Under the new structure, the prescriptive paths bring SHGC limits directly into the mix, meaning glazing choices must meet climate-specific criteria. “We will see how these changes go in terms of SHGC and U-factor,” Baker said. “The code was asked to address this in highly efficient building envelopes to address overheating.”
This statement underscores the code’s dual focus: reducing heat loss while preventing unwanted solar gain that can drive cooling loads and occupant discomfort. For fabricators, it means product lines may need re-evaluation across different climate zones.
Coating Position and Glass Package Choices
Paul Bush of Vitro Architectural Glass noted that the new restrictions have reduced the number of products that can comply with the code. However, he offered practical guidance for those aiming to influence SHGC and U-factor. According to Building Enclosure, Bush suggested that increasing SHGC means placing the low-emissivity coating farther from the sun. “If you are trying to increase SHCG, you want to put your coating farthest from the sun,” he suggested. “That will increase your ER. To reduce the U-factor, use an extra glass lite – for example, a triple IGU.”
This advice highlights a key tension in modern fenestration design: the same low-e coating that reduces winter heat loss also reduces solar gain, which can be undesirable in colder climates or where passive solar heating is desired. Positioning the coating on a different glass surface changes how much solar energy passes through and how much heat is retained, directly affecting the Energy Rating. A triple insulating glass unit adds another layer and cavity, lowering U-factor but potentially complicating design and cost.
Frame Design vs. Glass Quality
Lisa Bergeron of JELD-WEN emphasized that improving U-factor is not just about glass. “Improving U-factors is often a tradeoff between better glass and a better frame,” said Bergeron. “The most efficient way to achieve a better U-factor is to lower the frame profile, therefore with more glass. It’s a bit of a balancing act.”
Lowering the frame profile means reducing the amount of frame area relative to glass area, which can improve overall thermal performance because the center-of-glass U-factor is typically better than that of the frame. But this also affects structural integrity, durability, and sightlines. Bergeron noted that windows have a large impact on mechanical systems. “A better U-value helps with less heat loss and more occupant comfort,” she said.
For specifiers, this means product selection must account for the entire assembly, not just the glazing unit. A low-U-factor glass package paired with a wide, conductive frame may still fall short of code targets, while a slim frame with a higher solar gain glass might overheat. The new SHGC caps add another layer to this balancing act.
Implications for Canadian Specifiers and Manufacturers
The NBC’s new SHGC limits are part of a broader move toward performance-based energy codes. Canadian fenestration standards, including CSA A440, provide the test methods and performance ratings that underpin NBC compliance, but the code itself now sets climate-zone-specific solar gain expectations. While the sources did not detail provincial adoption timelines, specifiers working in Ontario, for example, must track how the NBC intersects with provincial building code amendments.
Manufacturers will need to verify which products meet the new prescriptive SHGC caps in each climate zone. For buildings using the performance path, there is more flexibility, but energy advisors will need accurate SHGC and U-factor data for whole-building modelling. The panel, as reported by FGIA, examined practical implications including frame design, product testing, certification, and regional market requirements.
Specifiers should request certified performance data from manufacturers for each climate zone, because the new prescriptive path makes component-level SHGC a code requirement rather than a design option. The FGIA session marks an early industry response to the 2025 NBC changes, with more guidance likely as provincial authorities adopt the new provisions. For now, Canadian glazing professionals have a clearer picture of the three compliance routes and the product design levers that matter most: coating position, glass package configuration, and frame profile.