finally found an underlayment that lasts - what's your experience?

Had a client last year dead set on using recycled underlayment - trying to be eco-friendly and all that. Install went smooth, but about six months in, we had some weird condensation issues right where the north side got zero sun. Mold city. Maybe it was the batch, maybe just that spot, who knows. Anyone else notice the “breathable” claims don’t always pan out? Still better than felt in some ways, but I’m low-key skeptical about those hybrid options... are they just splitting the problems too?

I’ve wondered the same thing about those “breathable” claims. We tried a hybrid underlayment on our garage roof - supposed to be the best of both worlds, but honestly, it still had some moisture issues in shaded spots. Not as bad as felt, but not perfect either. Anyone actually seen a hybrid hold up well over a few years, especially in damp climates? I’m in the Pacific Northwest, so shade and moisture are just part of life here.

Anyone actually seen a hybrid hold up well over a few years, especially in damp climates? I’m in the Pacific Northwest, so shade and moisture are just part of life here.

I’ve seen similar issues - hybrids seem promising on paper, but in spots that never dry out, moisture still sneaks in. Did you notice any difference in how fast the underlayment dried after a storm? Sometimes I wonder if “breathable” just means it lets vapor through both ways... which isn’t always good. Have you checked for mold or rot under those shaded areas yet? That’s usually where problems show up first.

Sometimes I wonder if “breathable” just means it lets vapor through both ways... which isn’t always good.

That’s a fair point. “Breathable” can be a double-edged sword, especially where you’ve always got shade and dampness. I’ve seen hybrids do okay for a couple years, but the real test is those spots that never see the sun. If you haven’t found any mold or rot yet, you’re ahead of the game - most issues start small and hide under the surface. Keep an eye out, but it sounds like you’re on the right track.

“Breathable can be a double-edged sword, especially where you’ve always got shade and dampness.”

That’s spot on. I’ve replaced underlayment in valleys where the sun never hits, and even the “breathable” stuff can trap enough moisture to cause headaches. Once had a north-facing dormer that looked fine for years - until a big storm hit and water found its way in through some pinholes. Sometimes I wonder if we’re trading one problem for another with these new materials, but at least they’re lighter to haul up a ladder.