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Metal roof over unvented, spray foam attic

jenndaloop | Posted in General Questions on

New here, but I’ve been reading some of the related questions to mine, but I still can’t seem to find an exact answer.  Here goes…

We currently have a shingled roof on our 11-year old home in coastal southern NC. Our roof is a hot mess!  The 30-year architectural shingles have significant granular loss, peeling, vegetation growing on them, and other issues, and our roofer friend was pondering if our shingles were baking in the heat.  Inside the attic, our roof deck is sealed inside with 9-11ish inches of Icynene spray foam, directly sprayed on the roof ceiling (no barrier between the wood and Icynene).  The entire attic is also unvented.

We’ve had some leaks that took some time to notice because we couldn’t see the leaks in the spray foam until the moisture reached a ceiling below.  And the shingles are just a mess at 11 years old.

– We are wondering if we could install a metal roof over our sealed spray foam attic like this?  
– And what would be the major issues with installing metal roof over sealed attic? 
– Obviously we’d be in the same situation of not seeing leaks.
– I’m also wondering if a metal roof would be too hot and not able to breathe in our situation?  
– Any other issues to consider?  
– What would be best to install under a metal roof – is it still roofing paper? 
-And finally, can you install a solar panel on a metal roof?  We have a solar hot water heating system.  

Thanks in advance!

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  1. Expert Member
    Akos | | #1

    There is abosultely nothing wrong with installing metal roof over SPF. Works great. Most metal roof manufactuers require a synthetic underlayment as slip sheet, I would go with whatever the manufactuer recommends.

    Being unveted, your roof doesn't need to "breathe". Most metal roof profiles have decent channels as part of the profile and unless you really go out your way to seal it up, it will allow for a small amount of drying. This is more than enough to deal with any night time condensation. You are in warm enough climate that a lighter color cool roof might be worth it.

    For simple solar attachment pick a roof profile that is compatible with standing seam clamps such as . These make installing panels on the roof a snap.

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