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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:

QUICK PRIMER: Air Barrier v. Vapour Barrier

Shawna HendersonJanuary 05, 2015

An air barrier stops air from moving in or out of the conditioned space, effectively blocking the air pressure differences that drive the stack and wind effects. Air barriers can be in place anywhere in the building envelope, and there can be more than one air barrier. Air barriers can...