Membranes…Interior Air-Control Strategies That Can Work

This article first appeared on the Green Building Advisor Website.

I’m from Minnesota, one of the few areas in the lower 48 that still regularly uses polyethylene sheeting as a vapor retarder, we’ve become very good at detailing these interior membranes for use as an air barrier.  (The practice is also very common in Canada and Alaska.)  The average blower door test I conduct for new homes in my market has now moved below 2 ACH50, most achieving these scores only using an interior air control strategy.  I don’t recommend using poly in most cases, instead I suggest moving to a class II vapor retarder, (smart, variable, and responsive vapor retarders), these products can also be used for air control.  Installing the two products is similar, so, what are the tricks to an effective interior air barrier installation?

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Construction Design-Service Cavity

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There are many methods used to make a home airtight, it all comes down to one simple rule, continuity.  Continuity is easily attained when there’s nothing that penetrates the air barrier.  No electrical boxes, plumbing drains and vents or ducts that need to extend from inside a building’s envelope to the outside.  Of course, there are times when different things need to extend from inside to outside, like the need for an outside water faucet.  But there are also many occasions when different systems end up outside that don’t need to be outside.  For example, forced air heating and cooling ducts that leave the conditioned space of the home simply because there was no space to keep them hidden inside the home.  Planning a service cavity can help keep most mechanicals inside the building envelope. Continue reading “Construction Design-Service Cavity”

Construction Design-Interior Air Barrier? Exterior Air Barrier? Or Both!

When designing the concrete-less slab on grade home, I gave serious thought to the location of the air barrier.  I have used water resistive barrier (WRB) or house wraps for years without a good understanding how they work as an air barrier.  In my climate, most homes use polyethylene sheeting as an interior (and main) air barrier.  As it turns out, there are better choices. Continue reading “Construction Design-Interior Air Barrier? Exterior Air Barrier? Or Both!”