Standing Seam metal roof underlayment and possible problems

Guest User
Hi. I live in the rainy pacific northwest (think Seattle). I am considering a standing seam metal roof with peel & stick in the valleys and a synthetic breathable membrane over the entire roof. On top of this membrane we would be adding a 10mm thick breathable rainscreen 3D mesh. Right now I have some mold in my attic, very little, but some. I will be replacing the sheathing and starting from scratch. My question is, this whole metal roof is very costly and I am worried that I will have condensation problems that are even worse on the inside of the attic sheathing with the standing seam metal roof because it will lower my attic temperature and conduct more cold through the 1/2 inch plywood sheathing. Obviously, the underlayment and 10mm mesh will help with cold conductivity, but will this be enough in my climate with my humidity and temperatures? My soffit venting is not great, and the opportunity for ridge venting on the roof is not great either (as I have short ridges) but I have read that all the venting in the world won't make a difference if you are losing moisture into your attic. Unfortunately, we have an old home, and can't just rip out the whole ceiling and start from scratch. Would we be better off installing an ashphalt roof and replacing it in 20-30 years and ripping out the sheathing again if we have mold issues? This would be half the cost of standing seam metal.
Todd Miller
Isaiah Industries, Inc.
Ted, I feel like you're taking a lot of the right steps to avoid problems. Ultimately, I feel pretty good about what you're doing and think it will make a good system. I really would suggest getting ventilation up there if at all possible. Some is far better than none / almost none. A great resource for ventilation information is Feel free to email me if you have more questions or need help sourcing the breathable underlayment and mesh. My email is [email protected]
Eric Novotny
An informed customer is the Best Customer!
Definitely need to know more about the ventilation of the attic currently as well as all the mechanically, plumbing, and attic connectivity with the living spaces below.

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