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Basement insulation questions

mcervinojr | Posted in General Questions on

Hey all.  Great community you have here.

I’m refinishing my basement and I live in a 5A zone (Northern, NJ).  I placed 1″ XPS against the walls and sealed seams w/ Tyvek Tape.  Framed w/ 2×4’s and installed batt insulation.  The batt that I installed has a Kraft paper on the side closest to the drywall.  Although it was too late, I read on here that unfaced would probably be a better option, so I took a razor knife and cut the paper vertically down.

Will I be OK?  I don’t want to have a double moisture barrier.  Thats my main concern.

Also on one side of the house, the face of the 2×4’s for the wall framing extend about 6″ from the concrete wall because of pipes running along the walls.  Hence, there is a gap between my rigid insulation and my 2×4′ batt wall.  Is there any concern with this?  I’ve omitted a vapor barrier.

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    >"Athough it was too late, I read on here that unfaced would probably be a better option, so I took a razor knife and cut the paper vertically down. "

    It will be fine, and the razor cuts really don't make an appreciable difference in the vapor permeance of the facer. (Vapor diffusion is about total area, not how air-leaky it is.)

    Kraft facers are more vapor-open than standard interior latex paint when the humidity in the cavity is approaching mold-risk territory, but fairly vapor tight when dry.

    >"Also on one side of the house, the face of the 2×4’s for the wall framing extend about 6″ from the concrete wall because of pipes running along the walls. Hence, there is a gap between my rigid insulation and my 2×4′ batt wall. Is there any concern with this?"

    The unobstructed vertical gap would be a code violation in jurisdictions that require fire stops.

    Not having an air barrier tight to the fiber insulation facing the air gap will reduce it's thermal performance somewhat, allowing air convection in/out of the fiber and air gap.

  2. GBA Editor
    Martin Holladay | | #2

    McErvino,
    If it's not too late, you should fill the 6-inch gap between the rigid foam and the 2x4 wall with additional fiberglass insulation.

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