Haha, yeah, I’ve definitely chased my fair share of synthetic underlayment down the street—those rolls have a mind of their own when the wind’s up. I totally get what you mean about the old felt just turning into a soggy mess. Around here, if you don’t have good attic airflow, it’s like a rainforest up there. I’m still figuring out the best combo of underlayment plus ventilation. Every time I think I’ve got it dialed in, some weird insulation patchwork throws me for a loop... but hey, keeps the job interesting, right?
I hear you on the attic turning into a rainforest—humidity’s a nightmare. Have you noticed any difference in how various underlayments handle that moisture, or is ventilation still the big factor? I’m always second-guessing if it’s the product or the airflow that matters more.
I’ve seen folks invest in top-notch underlayment, thinking it’ll solve everything, but if the attic’s not breathing, it’s just a bandaid. There was this place I inspected last winter—brand new synthetic underlayment, but the vents were basically useless. Still had condensation dripping off the rafters. Honestly, I’d rather have decent felt and good airflow than the fanciest product with poor ventilation. You can’t outsmart humidity if it’s got nowhere to go...
I get where you’re coming from—ventilation is massive, no question. But I’ve seen some pretty wild stuff with underlayment lately, especially the newer synthetics. On one job last fall, the attic vents weren’t great but the synthetic underlayment still made a difference. The homeowners had a leaky ridge cap during a storm, and the water sat there for hours before they noticed. The felt on their neighbor’s house basically turned to mush in the same situation, but the synthetic held up and kept the deck dry.
I’m not saying you can just slap fancy underlayment on and ignore airflow, but I do think it’s more than just a bandaid if you live somewhere with wild weather swings. Maybe it’s not a fix-all, but it sure buys you some time when something else goes wrong. Wouldn’t want to skimp on either one, honestly… airflow and decent materials both matter.
I’m not saying you can just slap fancy underlayment on and ignore airflow, but I do think it’s more than just a bandaid if you live somewhere with wild weather swings.
That’s a fair point. I’ve seen similar results with synthetic underlayment—especially in climates where freeze/thaw cycles are brutal. We had an ice dam last winter and the synthetic layer kept water from soaking the sheathing, which was a lifesaver. Still, I’d argue nothing replaces proper ventilation in the long run. The best underlayment just buys time, like you said, but if the attic’s a sauna, problems are going to stack up eventually. Both matter, but I’d never skip venting even with the “miracle” synthetics.
