Air sealing electrical penetrations through ext wall (+CEI)
Hi all,
This may be just a sequencing problem, but I’m not sure how which is the best way air-seal electrical penetrations (12-2 NM wire for outdoor outlets, 14-2 NM for outdoor sconces) to the plywood sheathing air-barrier.
Im currently laying-out wall penetrations in preparation for installing CEI (cork panels). I wasn’t planning to pull cable at this stage, so I had initially planned to install short pieces of pvc conduit at each penetration, air-sealed to sheathing, with CEI mounting blocks (as in photo of sillcock, attached).
Now I’m wondering if it’s better to delay installing CEI until I can pull cable (just those circuits that penetrate ext wall), then air-seal with the “one wire, one hole” method using caulk or Siga fentrim gaskets (see photo), which seems to be preferred by Randy Williams in his article https://www.greenbuildingadvisor.com/article/air-sealing-electrical-penetrations. Then fit CEI over the wire-ends.
Any thoughts or experiences are appreciated!
Adam
More info- zone marine 4c
Exterior walls are as follows (outside to inside);
Vertical cedar siding,
rainscreen battens,
WRB,
1.5” cork CEI,
plywood sheathing (air-barrier)
2×6 framing,
smart vapor retarder,
electrical chase (for remaining electrical circuits not penetrating the air-barrier)
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Replies
You can used canned foam around a conduit stub. I've done that many times. For inside the conduit, you can use "duct seal", which is a clay-like material sold in 1 pound bricks that is intended for this sort of thing. When using duct seal, get your hands wet first -- that will help keep the stuff from sticking to your skin. I have found that duct seal tends to dry out and stop sealing well after 10-15 years or so, especially when exposed to sunlight, so keep that in mind.
What I've often done in this sort of situation is to use some large diameter backer rod stuffed in the conduit as an air seal. This isn't a perfect seal, but it's better than nothing and it's easily removed if needed in the future. The material isn't approved for this application though, so it's not technically to code, so keep that in mind.
Bill
Both of the methods you show can work fine. I've done both successfully and both have their advantages. Like you said, it's mostly a question of logistics. If your exterior lighting and electric plan is pretty well defined, I find that method 2 is a bit easier to install. With the wire sealed to your air barrier, you can pretty much do what you want after that. On my current build, our strapping and siding stackup work almost perfectly to use a 6"x6" block of 2x material for fixture mounting and the electric boxes can be fastened right to the sheathing. We sealed the cables to the sheathing (air and water barrier) using the same Siga Wigluv tape that we're using for most of our other air-sealing.
Thanks for the replies. Sounds like either will work out, and I think I’ll make an attempt to run the exterior circuits first so I can eliminate the need for the conduit. Appreciate it!
Adam