"It lets moisture escape without letting water in...kind of like Gore-Tex for your roof."
Haha, love that comparison—Gore-Tex for roofs is exactly how I explained it to my neighbor last summer when he was dealing with some weird attic dampness. Funny enough, we both had similar houses built around the same time (late 70s), and we both started noticing issues around the same period. I initially thought it was just a ventilation thing too, but after installing ridge vents and soffit vents, it still wasn't perfect.
Eventually, I bit the bullet and opted for a breathable synthetic underlayment over the traditional felt when I re-roofed. Honestly, wish I'd done it sooner. Felt's good in theory, but I've seen firsthand how easily it can trap moisture, especially if there's any slight imperfection in installation. My uncle, who swears by felt ("been using it since before you were born," he always reminds me), finally admitted even he noticed condensation under his shingles last winter. That was a big deal coming from him—he's stubborn as heck about his methods.
I think part of the issue is climate-related too. If you're somewhere with big temperature swings or humid summers and cold winters, the underlayment choice matters even more. Here in the Midwest, we get both extremes, so something breathable makes sense. Not saying synthetic membranes are perfect—I've seen some cheaper ones tear or degrade if left exposed too long during installation—but overall, they've held up better than felt in my experience.
So yeah, totally agree attic venting alone might not cut it. A breathable membrane really complements good ventilation and insulation. It's like giving your roof a fighting chance against moisture buildup before it becomes a headache down the road.
Glad to see someone else mentioning climate factors—often overlooked, but they're definitely important. I've inspected countless attics here in the Northeast, and even with textbook-perfect ventilation setups, moisture issues still pop up if the underlayment isn't breathable enough.
"Felt's good in theory, but I've seen firsthand how easily it can trap moisture"
Exactly. Felt has its place, especially considering cost-effectiveness, but synthetic breathable underlayments really shine in areas with drastic seasonal changes or humidity swings. I recently did an inspection on a home built in '82 that switched to synthetic during their last roof replacement—huge difference. The attic was bone dry, insulation was performing well, and no signs of mold growth. Felt roofs of similar age typically show at least some condensation staining by now.
Great call on making the switch; your uncle's admission cracked me up (I've encountered plenty of traditionalists myself). It can be hard convincing folks who've relied on felt for decades...but seeing is believing, right?
I've been weighing the switch myself, but budget's a bit tight right now. Wondering if anyone's noticed a big enough difference in heating/cooling costs after switching to synthetic to justify spending extra upfront? Curious if it pays off long-term...
Switched to synthetic about two years ago—here's what I've noticed:
- Heating/cooling bills dropped slightly, but honestly, not a huge difference month-to-month.
- Biggest perk was comfort—rooms felt more consistent temp-wise, fewer drafts.
- Long-term durability is legit; seen fewer moisture issues and less wear overall during inspections.
- If budget's tight, maybe hold off until you're already planning roof work or major renos. Easier to justify the upfront cost then.
- Bottom line: savings alone probably won't blow you away, but comfort and longevity might tip the scales.
Just my two cents from what I've seen out there...
"Biggest perk was comfort—rooms felt more consistent temp-wise, fewer drafts."
Totally agree with this. I've inspected plenty of homes that switched over to synthetic underlayment, and the difference in comfort is noticeable right away. Homeowners often mention fewer cold spots and drafts, especially in older houses.
You're spot-on about the savings too—it's usually modest at best. But from what I've seen, the real value is long-term durability. I've come across roofs with synthetic underlayment installed 5+ years ago, and they're consistently holding up better against moisture and general wear compared to traditional felt.
Good advice on timing it with other major work; makes the upfront cost easier to swallow. Sounds like you've made a solid choice overall... nice to see others noticing similar results out there.
