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Do I need to vent soffits in with an unvented roof assembly?

user-471779 | Posted in General Questions on

I have large 4 foot exterior soffits. I am spray foaming the inside of the roof, an unvented attic assembly. Do I still need to vent my exterior soffit overhangs? Do I need to worry about the air trapped in that cavity if I do not?

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  1. GBA Editor
    Martin Holladay | | #1

    Q. "Do I need to vent soffits in with an unvented roof assembly?"

    A. No.

  2. Expert Member
    ARMANDO COBO | | #2

    Even though codes do not require it, I do vent all my soffits and parapet walls in unvented attic assemblies. I'm of the opinion that when the overhang cavities get wet, there should be a way to dry. There is no cost increase to use ventilated soffit material, and I rather be safe than sorry. I call it risk management.

  3. GBA Editor
    Martin Holladay | | #3

    Your approach is harmless. However, soffit cavities shouldn't get wet unless you have a roof leak or an ice dam -- and if you have one of those problems, a soffit vent won't solve it.

    Moreover, ventilation sometimes raises the humidity level of a cavity rather than lowering it, as anyone with a vented crawl space soon learns. This would rarely be a problem with a soffit -- but during the summer, if a hot, humid day follows a cool night, introducing outdoor air into the soffit will make the wood more damp, not dryer.

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