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Achieving air tightness with interior polyethylene

Jason Smith | Posted in Energy Efficiency and Durability on

A lot of guidance available regarding air tightness focuses on exterior air barriers. Here in marine 4, in western Canada, I am planning to use a polyethylene sheet system for my air barrier.

Our code/my energy advisor requires I achieve 3 ACH @50pa. Can anyone point me to some details and resources to help me achieving this in a self build? 

im wondering if I should be concerned about air leakage beyond the poly or simply just focus on one contiguous poly envelope? 

for example, should I also tape my sheathing, seal at the foundation and try an make this air tight? 

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Replies

  1. Expert Member
    Malcolm Taylor | | #1

    Jason,

    There is no reason you can't get good levels of airtightness with poly. The knock on using it is it can create a wrong side vapour-barrier in cooling climates, not that it isn't effective. The tightest house ever tested was air-sealed using poly.

    Use the approved tape to join sheets or seal bigger penetrations. For smaller ones use caulk. Run a bead of acoustical sealant or flexible caulk along the bottom plates on walls where they meet the subfloor - then bed the poly in it. Attach 12" strips of poly on the exterior walls where they will intersect with interior ones during framing. You also want to sandwich 12" strips of poly between the two top plates on interior walls below roofs or attics. Use airtight electrical boxes.

    A secondary air-barrier (like taping the sheathing) does add both increased air tightness, and redundancy. If it's simple to do and not too expensive, y0u might consider it.

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