I hear you about ventilation, but I’ve actually seen those breathable synthetics make a difference after hail storms. Had a client last spring—old farmhouse, lousy attic airflow, but the synthetic underlayment kept the decking bone dry after a nasty leak. Traditional felt would’ve turned to mush. It’s not a cure-all, but in my experience, it buys you time when things go sideways. Maybe not a replacement for good venting, but definitely worth considering if storms are frequent where you are.
That’s interesting, but does synthetic actually help with long-term moisture issues if the venting is bad? I get that it holds up better than felt in a storm, but I worry it might just hide bigger problems. Anyone seen rot or mold sneak up even with the fancy underlayments?
I’ve wondered the same thing, honestly. I swapped to synthetic underlayment last year thinking it’d be a magic fix, but my attic’s still a sauna in summer. Turns out, if your venting stinks, nothing under the shingles is gonna save you from moisture creeping in. I haven’t seen mold yet, but I did find some sketchy soft spots near the eaves—probably from trapped humidity. Synthetic’s tougher than felt, sure, but it’s not a get-out-of-jail-free card for bad airflow. If the roof can’t breathe, you’re just hiding the problem under fancier plastic.
Synthetic’s tougher than felt, sure, but it’s not a get-out-of-jail-free card for bad airflow.
Totally agree with this. I got all excited about synthetic underlayment too—felt like I was upgrading to the “pro” version. But after a summer of attic heat that could bake cookies, I realized venting matters way more. My step-by-step: 1) Checked soffit vents (half were blocked by insulation), 2) Cleaned out ridge vent, 3) Added a fan. Still not perfect, but at least my eaves aren’t mushy anymore. It’s wild how much just moving air around helps.
Funny, I had the exact same “aha” moment after my first winter in this house. I figured new synthetic underlayment would be the magic fix for everything, but nope—my attic was still a sauna in July and an icebox in January. Turns out, whoever insulated before me just stuffed batts right over the soffit vents. Didn’t even realize until I crawled up there and saw it myself.
Clearing those out made a bigger difference than any fancy material. I did end up adding a solar-powered vent fan too, but honestly, just getting air to move was half the battle. Still get some heat buildup on those 90-degree days, but at least my upstairs doesn’t feel like a greenhouse anymore.
One thing I learned: you can buy all the “upgrades” you want, but if the basics aren’t right—like airflow—it’s just money down the drain. Roofs are way more about balance than I ever expected...
