Discover the 4 Main Characteristics of the CAN/ULC-S741 and S742 Canadian Air Barrier Standards

Published by Jean-François Côté

CAN/ULC-S741 and CAN/ULC-S742—published in 2008 and 2011, respectively—are the first Canadian standards related to air barrier materials and assemblies. The first covers air barrier materials, while the second was developed for air barrier assemblies. Read on to discover the 4 main advantages of these standards.

#1. CAN/ULC-S741 and S742 Are Specifications, Not Test Methods.

While most existing standards for air barriers are test methods, CAN/ULC-S741 and S742 are specifications. They indicate the procedures to test the air leakage rate of materials and assemblies by referencing appropriate ASTM standards, and they include performance requirements. For air barrier assemblies, a five-level classification (A1 to A5) is included in S742 Standard, allowing professionals to easily compare performance levels.

#2. Test Methods for Assemblies Are Rigorous and Adapted to the Canadian Climate.

CAN/ULC-S742 helps professionals design more durable and energy-efficient buildings by providing stringent test methods that are adapted to the Canadian climate. The standard requires testing air barrier assemblies at ambient temperature and in winter conditions. The exterior sides of tested systems are exposed to -20 °C, while the interior sides are maintained at 20 °C.

#3. The Assemblies Are Tested to Handle Wind Pressure Loading Cycles.

Air barrier systems are exposed to various loads during their service life. CAN/ULC-S742 recognizes the impact of these loads and requires air barrier assemblies to be exposed to wind pressure loading cycles. Static pressures maintained for one hour, and cyclic, three-second gust loads are applied to the assemblies before measuring the air leakage rate.

#4. The CAN/ULC-S742 Standard Includes More Than Just Wall Air Barriers.

The key for high-performing air barrier systems is the continuity, which includes junctions between adjacent systems and a good roof air barrier. CAN/ULC-S742 can be applied to roof air barrier assemblies if the designated plane of airtightness is a low-sloped membrane roof system and the roof membrane serves as the air barrier material. If so, the air leakage rate is then measured using CSA Standard A123.21.