It’s been estimated that over the course of a heating season about one third of a litre of water can pass directly through gypsum board without a vapour retarder, and that 28 litres of water can pass through the same gypsum wall with just a 1" x 1" hole in that same time period.1
1Builder’s Guide to Cold Climates, Joseph Lstiburek
In winter, warm, humid air moves naturally from building interiors to colder, drier exteriors. Without air barriers, moisture will condense on the colder, inside surface of the exterior wall.
In summer, warm, humid air moves naturally from building exteriors to cooler, drier interior areas. Without proper air and vapour control, moisture will condense on the colder, inside surface of the interior wall.
Modern buildings can be affected by many environmental challenges that can significantly affect their performance. Common environmental challenges of buildings include wind pressure, fan pressurization, stack pressure, barometric cycling and thermal cycling. A continuous air barrier helps maximize building efficiency.
Protecting buildings with a continuous 3M™ Brand Air Barrier System can provide a wide range of benefits, including:
• Better indoor air quality
• Less risk of mould and mildew compared to most traditional air barrier systems
• Happier, healthier residents
• Extended service life and durability of your building
• Energy savings through the reduction of unintended air movement
Depending on their material characteristics, air barriers can control or block the passage of water vapour. Choosing the right air barrier system is dependent on the kind of wall assembly you are constructing (the primary driver), your climate location (secondary driver), and your goals for sustainable construction.
Once you have selected a wall assembly design, the application temperature and weather conditions will determine the best barrier type. For example, cold or wet weather may eliminate some coatings and sheet membrane systems from consideration.
Air barriers are permeable systems that allow vapour transmission through a wall assembly. The perm rating is typically greater than 10 (“perm rating” is a measure of the diffusion of water vapour through a material).
These nonpermeable systems stop air and moisture transmission through the wall assembly. They typically have a perm rating of less than 1.0.