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Polyiso insulation behind fiberglass

ogZKx6bHQk | Posted in Energy Efficiency and Durability on

Hi All,

I am remodeling a bathroom and have all the drywall off. The home is 40 years old, and 3 1/2″ foil faced fiberglass insulation was used in the walls and the ceiling. It is in good shape. I have several sheets of used, 3″ thick polyiso insulation, black paper faced (not foil). I was thinking of removing the fiberglass, then putting polyiso behind it, then replacing the fiberglass. Anyone see any problems with this (moisture, mold, etc).


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  1. GBA Editor
    Martin Holladay | | #1

    I don't think you'll have any problems, as long as you air seal the perimeter of each piece of rigid foam, using caulk, canned spray foam, or high quality tape.

  2. ogZKx6bHQk | | #2


    thanks for the response. I'm looking forward to a little warmer bathroom.

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