Is it harder to find roof damage if spray foam insulation is installed?

1,616 Views | 11 Replies | Last: 6 yr ago by Builder93
sims05
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AG
I'm looking into adding spray foam insulation under the roof deck of an older home. It would effectively seal off the attic space. I've seen some of the threads on here but don't think I have seen the following discussed.

Once the foam goes in under the decking, is it possible to tell if there is any damage to the decking, from a leak for example, without removing the roof covering? I see the benefit of the insulation but am wondering if it comes at a cost of missing a problem down the line with the roof.
Wildman15
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AG
Most likely, if you get a leak it won't be because of the decking or roofing material, but because of your flashing.

Edit: I would also make sure whatever material you have for the actual roof (shingles, metal, etc) can still comply with spray foam. Most will still require some sort of ventilation
The Fife
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Flashing or valleys, it's always one of the two...
Aggietaco
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AG
To answer your question, yes.

You also need to revisit your current exhaust, fresh air, and combustion air strategies if you are air sealing your attic with spray foam at the roof deck. It's a great practice, just requires a bit of re-work to existing systems.
Ovalo
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AG
DON'T use closed cell foam on the roofdeck of a wood structure. It's waterproof and doesn't show leaks.

Open cell foam is a good insulation product and it allows moisture to migrate thru. It also has the advantage of reducing sound.
shalackin
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AG
It makes it more difficult to find leaks from the attic side. But as mentioned above, good roofers will know how to diagnose issues regardless of spray foam insulation. I wouldn't hesitate on spray foam due to that issue.
jt2hunt
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AG
Why do they recommend closed cell in the attic?
sims05
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Thanks for the replies. It gave me a couple of follow up questions to consider before committing to the work being performed.
Ovalo
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AG
I've been a spray foam contractor for 10 years and have attended numerous building science classes. Don't know anyone that recommends closed in a wood attic. Years ago, companies would recommend their closed cell foam in the attic but I think they did so because they only sold closed foam.

On the practical side of using closed cell in an attic, rafters and decking are at risk of rotting with waterproof insulation sprayed to roof deck. To my knowledge, code allows either.
jt2hunt
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AG
So, open cell in the attic. What do you need to do with ventilation? Do you need to adjust your hvac system to spray a 30 year old attic?
Wildman15
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What makes up your actual roof? Asphalt shingles? Metal? Tile?
jt2hunt
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AG
Asphalt shingle on plywood deck.
Builder93
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You should use an ice and water shield as an extra barrier under the final roofing material.
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