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Using ZIP R Sheathing

user-2310254 | Posted in Green Building Techniques on

I’m using ZIP R sheathing on the exterior walls and wonder if it is a good option for the roof. I was considering exterior insulation, but it is a more complex solution than my framer may be willing to tackle. I’ll probably go with closed cell against the sheathing and then another type of insulation to achieve the required R value. If I used this strategy, should I have the plan ZIP panels for the roof sheathing?

And yes, I’m aware of the growing controversy concerning spray foam. I would prefer not to use it, but I have to keep this project moving along.

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  1. GBA Editor
    Martin Holladay | | #1

    If you want to install rigid foam on top of your roof sheathing -- and it's an excellent approach -- you have to install foam that meets the minimum R-value required by code. You can't use Zip R sheathing for roofs -- at least not without additional rigid foam -- because the R-value is too low.

    The minimum R-value for continuous rigid foam at the roof sheathing layer depends on your climate zone:

    R-5 foam for Climate Zones 1-3,
    R-10 for Climate Zone 4C,
    R-15 for Climate Zones 4A and 4B,
    R-20 for Climate Zone 5,
    R-25 for Climate Zone 6,
    R-30 for Climate Zone 7, and
    R-35 for Climate Zone 8.

    More information here: How to Build an Insulated Cathedral Ceiling

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