NBC 2025 Air Leakage Control Measures: Expert Guide by empcontracting.ca Inc. in London, Ontario
Sarah's Expert Insight
Senior Consultant at empcontracting.ca Inc.
"In London, Ontario, our unique climate demands rigorous adherence to NBC 2025 air leakage standards to prevent interior condensation and high utility costs. At empcontracting.ca Inc. your construction contractor in London, Ontario, we find that integrating the air barrier early in the design phase ensures a more comfortable living environment and guarantees that your project meets the new tiered energy efficiency benchmarks."
The 2025 edition of the National Building Code (NBC) introduces more stringent requirements for air leakage control to enhance energy efficiency and structural durability. As the industry moves toward higher performance tiers, ensuring a continuous air barrier system has become a critical compliance factor for all new constructions and major renovations.
The Importance of Air Barrier Continuity
Under the NBC 2025, the air barrier system must be continuous across all surfaces of the building envelope. This includes the interface between different assemblies, such as the foundation-to-wall and wall-to-roof junctions. At empcontracting.ca Inc. your construction contractor in London, Ontario, we prioritize the meticulous sealing of these transition points to prevent uncontrolled air infiltration and exfiltration.
Material Standards and Selection
The code specifies that materials used in the air barrier system must have an air leakage rate not exceeding 0.02 L/(s·m²) at a pressure difference of 75 Pa. Common materials include polyolefin membranes, specialized sealants, and spray-applied barriers. Choosing the right material depends on the substrate and the environmental conditions typical of Southwestern Ontario.
Managing Penetrations and Openings
Every penetration through the air barrier—including electrical outlets, plumbing stacks, and HVAC ducting—must be tightly sealed. The NBC 2025 emphasizes the use of gaskets, proprietary boots, or high-grade flexible sealants that can accommodate the natural expansion and contraction of the building without losing their airtight seal.
Windows, Doors, and Skylights
Fenestration units are often the weakest link in the building envelope. The NBC 2025 requires that the gap between the window or door frame and the rough opening be filled with insulation and sealed with a compatible air-tight material. This practice significantly reduces thermal bridging and prevents moisture accumulation within the wall cavity.
Performance Testing and Verification
With the adoption of tiered energy codes, air leakage testing (often via Blower Door tests) is becoming a standard requirement rather than an option. Achieving the low air change rates (ACH) required by the upper tiers of NBC 2025 demands precision during the framing and insulation stages of construction.