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Vented and unvented roof combo

user-6610183 | Posted in Building Code Questions on

Is it possible to have a combination vented and unvented roof assembly? I own a house in southern Maine that has a vented roof. The house also has cathedral-style ceilings in two upstairs bathrooms, and it’s the roof above these bathrooms where I’ve recently identified an ice dam. Because the bathrooms have skylights, where venting may by difficult, my thought was to constructed an unvented roof over those two rooms and leave the rest of the attic roof vented. I have no plans to convert this space to a livable area in the future so changing the who roof seems unnecessary. I’m wondering if the code allows this, or if there something about my plan that will doom it to failure because of some air/vapor transport mechanism I’m not considering.

Any help would be appreciated.

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  1. GBA Editor
    Martin Holladay | | #1

    If I'm understanding your question correctly, there's no reason to worry. Many houses have some roof sections that are vented, and other roof sections that are unvented.

    This approach can work fine, as long as each type of roof is well detailed and as long as each type of roof has adequate R-value. For information on getting the details right, see How to Build an Insulated Cathedral Ceiling.

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