Had a roofer once tell me, “Felt’s like your favorite old flannel—breathes great, but don’t leave it out in a hurricane.” I’ve seen both hold up fine if the crew moves quick. Down here in muggy Florida, that breathability thing actually matters.
That’s a great comparison with the flannel. I’ve always heard felt is more forgiving in terms of letting moisture escape, but it definitely can’t handle sitting exposed for days, especially if a storm rolls in. I’m in central Florida too and honestly, the humidity here just wrecks anything that traps moisture. I went with synthetic last time because my roof has a pretty low slope and I was worried about leaks during installation delays. It seemed to shed water better, but I do wonder if it traps more heat underneath? Hard to say if that impacts shingle life or not, but I haven’t noticed any issues yet.
I’ve wondered about the heat thing too, especially here where the sun cooks everything by noon. I used synthetic on my last job and yeah, it felt hotter in the attic, but honestly, I think the shingles themselves make a bigger difference. Haven’t noticed any extra wear yet, but I do check after every storm just in case.
I used synthetic on my last job and yeah, it felt hotter in the attic, but honestly, I think the shingles themselves make a bigger difference.
That’s interesting—I've always been a bit skeptical about the claims around synthetic making attics hotter. In my experience, shingle color and ventilation seem to play a much bigger role in attic temps. I’ve seen dark shingles with good airflow keep an attic cooler than light shingles with poor venting, regardless of what’s underneath.
Here’s how I usually look at it:
1. Check roof ventilation—ridge vents, soffit vents, etc. If those aren’t working right, no underlayment will help much with heat.
2. Look at the shingle type and color. Lighter colors do reflect more, but sometimes folks forget about that.
3. Then decide on underlayment. Synthetics are tougher against tearing and water, but I’ve heard some folks say they can trap more heat. I’m not totally convinced, but I get why it’s a concern.
Have you noticed any difference in shingle wear or attic moisture since switching to synthetic? I’ve had a couple jobs where felt actually held up better in humid stretches, but maybe that’s just our weird local weather.
Synthetics are tougher against tearing and water, but I’ve heard some folks say they can trap more heat. I’m not totally convinced, but I get why it’s a concern.
Yeah, I’m with you there. In my buildings, ventilation and shingle color have always made the biggest impact. Synthetics might get blamed for heat, but honestly, I’ve never seen measurable attic temp differences just from swapping underlayments. Moisture is a bigger worry for me—felt can sometimes handle our muggy stretches better, but synthetic is way less likely to tear if you’re dealing with foot traffic or a long dry-in. It’s a tradeoff, but your priorities sound spot on.