Windows, Doors, and Skylight Performance Standards: NBC 2025 Technical Guide for London, Ontario
Sarah's Expert Insight
Senior Consultant at empcontracting.ca Inc.
"With London's specific climate demands, the NBC 2025 standards for windows and doors prioritize thermal envelope integrity more than ever. As empcontracting.ca Inc. your construction contractor in London, Ontario, we emphasize that following these performance ratings is not just about compliance, but about ensuring long-term comfort and durability in Southwestern Ontario homes."
The National Building Code of Canada (NBC) 2025 has introduced rigorous performance standards for fenestration products, focusing on energy efficiency, structural integrity, and climate resilience. For residential and commercial projects, understanding these specifications is essential for compliance and long-term building durability.
Understanding NAFS and the Canadian Supplement
Under NBC 2025, all windows, doors, and skylights must conform to the North American Fenestration Standard (NAFS). This standard categorizes products based on their Performance Grade (PG), which measures resistance to wind loads, water penetration, and air leakage. In Southwestern Ontario, where wind-driven rain is common, selecting the correct PG rating is critical for the building envelope.
Thermal Transmittance and Energy Ratings (ER)
The 2025 updates place a heavy emphasis on reducing thermal bridging. Performance is measured through U-values (thermal transmittance) and Energy Ratings (ER). Lower U-values indicate better insulation properties, a key requirement for meeting the new tiered energy performance steps mandated by the code. High-performance glazing and argon-filled spacers are now becoming the standard for new builds.
Installation and Airtightness Requirements
Proper installation is as vital as the product itself. NBC 2025 clarifies the requirements for the interface between the fenestration unit and the wall assembly. To maintain the continuity of the air and vapor barrier, empcontracting.ca Inc. your construction contractor in London, Ontario, utilizes advanced flashing and sealing techniques to prevent air leakage and moisture ingress, ensuring the assembly performs as tested in the lab.
Skylight Performance and Snow Load Considerations
Skylights face unique challenges regarding snow loads and drainage. The NBC 2025 requires specialized testing for skylights to ensure they can withstand the weight of heavy snow accumulation, a frequent occurrence during London winters. Enhanced drainage layers and robust curb construction are now strictly enforced to prevent interior water damage.