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Attic air sealing with tape?

user-6798160 | Posted in Green Products and Materials on

I have a 1926 Cape in Seattle, WA (zone 4C) and the attic is in desperate need of insulation and air sealing (at least the half that I can reach). The ceiling and walls below are plaster and lathe and the insulation shows little darkening from the ceiling, just from the penetrations. The walls in the upstairs are drywall.

I know I have to crawl in there and air seal as much as I can before we add more insulation, but since this will already be a messy job, I’m hoping that I can use high quality tape instead of acoustical sealant. Does anyone have any comments on how well that sticks to wood or what I can do to improve the seal to wood? Does anyone just buy a roll of air barrier and run it all along the attic floor?

Thanks very much

PS. Yes, we have insulated ducts in there and yes, I’m looking to see what I can do to insulate the roof deck, but that has to wait until we know what kind of modifications to make to the roofline.

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Replies

  1. user-6798160 | | #1

    I forgot to mention that I'm also interesting in using tape to air seal the mud sill in the basement (instead of acoustical sealant). It means that I should be able to do that part first, then the subsequent earthquake retrofit won't be as messy.

  2. GBA Editor
    Martin Holladay | | #2

    Kathryn,
    Here is a link to an article that explains the work you intend to do: Air Sealing an Attic.

    There aren't many opportunities to use tape in this type of work, but tape is sometimes handy -- for example, to seal the crack between a partition top plate and a plumbing vent pipe, or to seal the crack between a partition top plate and a duct.

    You'll probably find yourself using a lot of canned spray foam for this work.

    You mentioned an "attic floor." Does your attic have a partial floor? Or is there a floor over the entire attic? Does this floor consist of boards or plywood?

  3. user-6798160 | | #3

    Hello Martin,

    Thanks for responding. I've already read that article (and actually every article in "How to do Everything"). I was hoping to try something a little neater than spray foam, though it seems that polyiso and spray foam will be the obvious way forward. I'll try a little tape on some promising sections to see how well it works.

    When I said "floor", I just meant the 2x4 ceiling beams that I'm crawling over. The plaster and lathe is directly underneath with a stingy little batt of fiberglass between the beams.

    Thanks again.

  4. GBA Editor
    Martin Holladay | | #4

    Kathryn,
    As long as the surfaces are dust-free -- (it can be hard to find dust-free surfaces in an attic) -- you can use a high-quality tape like Siga Wigluv for many air sealing tasks. The main disadvantages to this approach are (a) you have to clean the surfaces first, and (b) high-quality tape is expensive.

    Remember that tape sticks better to smooth surfaces (planed lumber) than rough surfaces (rough-sawn lumber).

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