Had a similar experience myself—thought I was being clever by layering insulation with plywood cover boards. Seemed solid at first, but after a couple winters, noticed some damp spots forming. Turns out, even plywood can trap moisture if ventilation isn't spot-on. Ended up redoing the venting system, which helped a ton. Makes me wonder though, has anyone tried those breathable membranes instead of traditional vapor barriers? Curious if they'd make a noticeable difference...
I've seen a few folks try those breathable membranes, and honestly, I'm still not totally sold on them. In theory, letting moisture escape while keeping water out sounds perfect, but modified bitumen roofs can be tricky beasts. If your ventilation isn't dialed in first, even the best membrane won't save you. I'd say focus step-by-step: nail down proper venting first, then maybe experiment with membranes if you're feeling adventurous (and have some spare cash...). Just my two cents.
I've seen a few of these breathable membranes in action, and honestly, results were kinda mixed. Had one client swear by it, another swear at it... you get the idea. But here's what I'm wondering—has anyone tried pairing these membranes with spray foam insulation underneath? Seems like it could be a solid combo, or maybe I'm just overcomplicating things again. Thoughts?
I've actually seen this combo done on a job last year. The breathable membrane seemed fine at first, but once we sprayed foam underneath, things got tricky. We ran into some moisture issues because the foam sealed things up so tight, kinda defeating the purpose of the membrane. Might've been installation error or just bad luck...but I'd be cautious about mixing those two again.
Yeah, I've run into similar issues myself. The breathable membrane is meant to let moisture escape, but once you add spray foam, you basically trap everything in place. One thing I've found helpful is using rigid insulation boards instead of spray foam. You can layer them carefully, tape the seams properly, and still leave some controlled airflow gaps. Takes a bit more planning upfront, but it keeps moisture problems at bay... at least from what I've seen.
