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Bonfiglioli wall foam density?

andy_ | Posted in General Questions on

The EPS foam that the big box stores sell seems to be a pretty low density at 15psf, and the foamular XPS that’s 25psf is only stocked in 2″ thickness.
If I use the 15psf EPS at 1″ thick along with 1×3 strapping, will I get a “squishy” wall or will it still feel solid?
While I’m sure I could find a foam distributor or manufacturer that would have a more dense EPS, I’m only going to be needing a single sheet to do a single room.
Anyone here actually do a Bonfiglioli wall with big box EPS? How’d it go?
Thanks,
-Andy
Climate Zone 4

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    Even box store Type-I EPS will still feel pretty solid once it's up, but it's harder to make clean 1.5" wide strips out of that stuff without making a lot of foam-crumbs or breaking it, compared to foil faced polyiso.

    https://www.finehomebuilding.com/2009/01/29/theres-a-better-way-cutting-rigid-insulation

    1. andy_ | | #3

      Thanks for the info, I'll look at the polyiso.
      That sharpened putty knife technique you linked to works a charm! I've used that a few times now and it's by far the best method.

  2. Expert Member
    Michael Maines | | #2

    I don't think the Bonfiglioli approach is worth the effort in most cases, but if I were to do it, I'd buy ZIP-R insulating sheathing and rip it into strips. That way you get a nailer and high-R/in insulation with the least labor.

    1. andy_ | | #4

      Michael, I do agree it's not worth it in most cases but there are some situations where it makes sense even outside of DIYers who aren't counting labor as a cost.
      I've got two scenarios where I'm going to be using it. Renovating a room with 2x4 walls where the interior is getting demo'd down to the studs, and in a new build where one of the walls has so many studs and windows that I'm afraid to even consider what the whole wall R value would be without the thermal break of the Bonfig approach.

      1. Expert Member
        MALCOLM TAYLOR | | #5

        Is there an advantage in those situations to using Bonfiglioli framing over just putting an inch of foam over the wh0le wall?

        1. andy_ | | #6

          Good point Malcolm, my reasoning on the Bonfig is that it still gives me stud locations for attaching drywall, trim, and outlets. A whole wall of foam on the inside would make all that a little challenging. Unless you're talking about foam on the outside...but that ship has sailed as tearing apart siding and moving windows and exterior trim would be far more hassle at this point.

          1. raul4817 | | #7

            Andy,
            I have also contemplated both approaches but decided to settle on covering my entire wall with foam. This way you get your thermal break and the added r value for the entirety of the wall. 2nd reason was i can tape the seams and canned spray foam in the corners so the foam board can double as my air barrier. For drywall and outlet boxes i will frame up a 2x3 service cavity on the interior side of the foam board. If you dont want to frame up an entire wall you could easily attach 1x3 furring strips for hanging drywall or even 2x3 strips flat and move your electrical in that space without the extra care needed to air seal the outlet boxes.
            Raul

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