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Open cell spray foam in attic

home26 | Posted in Green Building Techniques on

I am renovating a house in South Florida built in 1976. There is a new shingle roof that was just installed, I’m looking to insulate the roof rafters with 5″ of open-cell spray foam and condition the attic.

Is this the way to go? I am getting conflicting information regarding open cell and closed cell.
Do I need a dehumidifier? 
I will be using a VRF HVAC system

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  1. ThirtyWest | | #1

    I'm no expert. But I have had problems with open cell foam. I'm in the northeast and it did suffer from the never-ending smell problem that others had talked about here. Actually, I just talked to a spray foam crew that said they hate open cell and would never use it in their own home. Some like it because it's apparently greener than closed cell during the installation.

  2. Jon_R | | #2

    With the less expensive open cell, you need to truly condition the attic - it shouldn't be humid up there. A dehumidifier will do that, even in mild weather when the HVAC isn't running. Ref: Joe Lstiburek.

  3. GBA Editor
    Brian Pontolilo | | #3

    Hi Home 26.

    You may find this article helpful: Open Cell Spray Foam and Damp Roof Sheathing.

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