I hear you on the breathability question. I had the same concern when I switched to synthetic underlayment last year. The stuff feels almost like plastic, right? But honestly, my attic’s been drier too, and I haven’t noticed any trapped moisture or weird smells. I think the key is having solid ventilation—ridge vents and soffits made a bigger difference than I expected. Maybe the underlayment just keeps the bulk water out, and the airflow handles the rest. Still, I do wonder if in super humid climates, the lack of breathability could be an issue long-term... but so far, no regrets here.
- Noticed the same thing with synthetic—feels weird at first, but attic’s been fine.
- I’m in the Midwest, so humidity’s up and down. Haven’t seen any condensation issues yet, but I keep a close eye during summer storms.
- Did you compare costs much? I went synthetic for durability, but the price jump over felt was a bit of a shock.
- Curious if anyone’s tracked energy bills before/after switching underlayment... Wondering if it actually helps with insulation or if that’s just wishful thinking.
Curious if anyone’s tracked energy bills before/after switching underlayment... Wondering if it actually helps with insulation or if that’s just wishful thinking.
I get this question a lot on inspections, and honestly, I haven’t seen much of a difference in energy bills just from swapping out underlayment. Most of the time, attic insulation and ventilation play a way bigger role. Synthetic underlayment is great for durability and water resistance, but it’s so thin that it doesn’t really add much R-value. I’ve had a few clients hope it’d make their upstairs cooler in summer, but if anything, it’s more about keeping leaks out than keeping heat in or out.
I’m in the upper Midwest too, and the humidity swings are wild. I’ve seen a couple of attics where folks were worried about condensation after switching to synthetic, but as long as the attic’s vented right, it’s usually a non-issue. The only time I saw a problem was when someone blocked off their soffit vents thinking it’d help with drafts—ended up with a damp attic and some mold. Not fun.
Cost-wise, yeah, synthetic’s a jump. I remember when it first started showing up, and folks were pretty skeptical. Now, most of the roofers I know won’t even touch felt unless someone’s really pinching pennies. The labor savings are real, though—synthetic’s lighter, goes down faster, and you don’t get those nasty tears if the wind picks up mid-job. I’ve seen felt blow halfway off a roof during a storm, but synthetic usually stays put.
One thing I do notice—synthetic can be a little slippery if you’re up there, especially with morning dew. Had a buddy nearly take a slide last fall. Just something to keep in mind if you’re the DIY type.
All in all, I’d say synthetic’s worth it for the peace of mind, but if you’re hoping for lower energy bills, attic insulation’s where you’ll get the most bang for your buck.
Are you guys sold on using a synthetic underlayment (for tile roof) with a built in radiant barrier?
I’ve actually had mixed results with those radiant barrier synthetics under tile. On paper, they sound great—extra heat reflection, longer lifespan, all that. But I did a job last year in a coastal area, and honestly, the difference inside the attic wasn’t as dramatic as I’d hoped. Plus, if the tile install isn’t spot-on, moisture can still find its way in, and synthetic doesn’t always dry out as fast as old-school felt. I still lean toward a high-quality synthetic without the radiant layer for most jobs. Less risk of weird compatibility issues, and it’s easier to work with if you’ve got a steep pitch or a lot of flashing. Just my two cents from the field...
