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Community and Q&A

Rigid foam board as a vent baffle

Thomas Muller | Posted in Energy Efficiency and Durability on

In a vaulted ceiling, if using one inch rigid foam board furred out a min of 1″ to provide ventilation from soffit to ridge vent followed by fiberous insulation such as fiberglass batts ……is this proper? would the one inch of foam used as a vent baffle be prone to condensation in a cold climate or does this particular situation not call for the min R-20 of foam? thank you in advance for the help.

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    If you are using rigid foam as a vent baffle, the best type of foam to choose is EPS (because it is somewhat vapor-permeable). The next best type of foam to choose would be XPS. I wouldn't use foil-faced polyiso if I were you. As long as your foam is only 1 inch thick, I think you'll be fine.

    Make sure to pay attention to air tightness when installing your vent baffles. For more information, see How to Build an Insulated Cathedral Ceiling.

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