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Can polystyrene foam be used as a thermal break on inside of exterior osb sheating?

user-7030272 | Posted in Energy Efficiency and Durability on

I am in zone 5 and building with 2×6 framing that will be filled with 5.5 inches of open cell spray. I know that 1/2″ is too thin for the exterior but have not seen any comments about putting it on the interior side of the osb . Thaks, Ohio Mike%

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  1. user-2310254 | | #1


    Have you considered the Bonfiglioli approach? I am not sure how thick you would have to go in Zone 5, but it is probably more than 1/2 inch.

  2. GBA Editor
    Martin Holladay | | #2

    The usual problem when anyone suggests installing a layer of rigid foam between the studs and the exterior sheathing is a structural problem. Engineers don't like it. The sheathing provides bracing for the wall, and the rigid foam introduces new calculations to make sure that the bracing needs are met.

    The problem is solved if you buy Zip-R sheathing -- a brand of OSB with polyiso foam on the interior side -- because the manufacturer (Huber) has done the engineering for you, and has obtained approval for their nailing schedule.

    Or, as Steve suggested, you can employ the Bonfiglioli approach. For more on the Bonfiglioli approach, see "Breaking the Thermal Bridge."

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