Many builders, renovators, and homeowners use the terms air barrier and vapour barrier interchangeably, but they perform very different jobs, even when the same material can be one or both. Learn how each system controls air movement and moisture, why confusing them can lead to condensation and durability problems, and how understanding the difference leads to better building envelope decisions.
Vapour Diffusion Retarders are Better than Vapour Barriers
Shawna HendersonAugust 09, 2023
In cold climates, the vapour retarder is installed on the warm side – typically directly behind the drywall. This location prevents the warm and relatively humid air from traveling into the wall where it may condense. But here’s the thing: Building scientists agree that the use of vapour impermeable retarders or barriers are not always necessary and in fact can be a poor strategy in all except the coldest climates such as northern Canada and Alaska. This is because the use of vapour impermeable barriers has two significant flaws: