Let the sheetrocking begin!

Well, at least for the 2nd floor ceiling.

Normally, you wouldn’t start the sheetrock till the walls are insulated. But in order to test how well (or poorly) we’ve sealed the house with a blower door test, we need to complete the air barrier, and that means the 2nd floor ceiling. This is the area where the air barrier transitions from the exterior of the house to the interior. It will be one of the trickiest areas to seal properly.

We installed gaskets around the top edges of the walls, but because we’re using strapping, it made it difficult to close all the gaps. So we’ve decided to use 2-part foam only around the edges where the ceiling meets the walls. This should ensure that we have all possible gaps sealed.

Lessons Learned

We used poly boxes at all exterior wall electrical box penetrations, but we totally forgot to do this at the 2nd floor ceiling. We’ll have to use a combination of tape and foam to seal light fixture electric boxes in the ceiling.

I think I’ve mentioned in an earlier post that a smarter way to air seal the top of the enclosure would have been to extend the exterior sheathing and air barrier over the ceiling joists. Then pile the roof insulation on top of the sheathing. This method has been used by Marc Rosenbaum, although the air barrier in this case was the roof.* This approach would necessitate raising the roof up a bit to ensure proper insulation levels at the eves. The extra expense of sheathing the top of the ceiling joists would have likely been offset by the extra labor and material costs spent sealing all the gaps with foam.

* http://www.southmountain.com/smclibrary/articles/2011_01_JLC.pdf

2 Responses to “Let the sheetrocking begin!”

  1. 1 Mary 21-August-2011 at 8:27 pm

    Hi, good progress! A few questions when you get a chance.

    You mentioned “strapping”, I’m not sure what you mean. Is it interior strapping to add depth to the wall insulation, i.e. a Mooney wall? Or something else?

    On the foam you used to seal little gaps, is that on the ‘room’ side of the dry wall or up on the attic side?

    I would llke to do a blower door test too on on our house. We’re currently about 80% through rough framing. It is great to read your blog and see how you’re going about it. Thanks for taking the time to document your project!


    • 2 Larry 23-August-2011 at 4:57 pm

      Hi Mary, good questions.

      The strapping was used on the inside of the ceiling joists only. It helps straighten out any warps or bows in the joists, giving you a flatter ceiling when you install the sheetrock. This detail has caused a lot of air sealing headaches, but it wouldn’t have been a problem if we had air sealed the envelope on top of the ceiling joists.

      We’re going to use foam on the attic side, only at the edges of the ceiling where it intersects walls, and at all other penetrations for electrical, plumbing and lighting fixtures (no venting passes through the attic space).

      Glad you’re enjoying our blog. Good luck on your framing and future blower door test.


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