If underlayments had a race: which one would cross the finish line last?

Had to laugh at the “race” idea—if underlayments were runners, old-school felt would be huffing and puffing at the back for sure. I’ve seen it curl up or just give out after a couple seasons, especially with our wild Midwest storms. I’ll admit, synthetic made me nervous at first too, but like you said,

“insulation and venting seemed to matter way more.”

Felt’s definitely the tortoise in this race, but not the wise, slow-and-steady kind—more like the one that stops for a nap and never wakes up. I’ve torn off roofs where the felt was basically confetti after a few years of Midwest humidity and freeze-thaw cycles. Synthetics have their quirks, but at least they don’t disintegrate if you look at them sideways. Still, you nailed it: attic venting and insulation do way more for roof longevity than any underlayment swap. Funny how folks obsess over the underlayment but ignore the real heavy hitters.

I just replaced the roof on my first house last fall—went with synthetic underlayment after seeing how the old felt had basically turned to dust in spots. Midwest weather really does a number on felt. I spent way more time researching venting and insulation than underlayment, honestly. It’s wild how much difference that makes for keeping the attic dry and the shingles from curling. Still, I get why people focus on underlayment... it feels like something you can control, but the real work is all that hidden stuff.

If we’re talking about which underlayment would “cross the finish line last,” I’d put my money on the newer synthetics, especially in climates like the Midwest. Traditional felt just doesn’t hold up the same way—seen too many tear-offs where the felt is practically gone or so brittle it crumbles in your hands. Synthetics don’t soak up moisture, and they’re much less likely to wrinkle or degrade if you get a stretch of rain before shingles go on. That alone makes a big difference for longevity.

But you nailed it about venting and insulation. Most folks focus on what they can see or touch, like underlayment or shingle type, but the real battle is in the attic. I’ve been on jobs where the homeowner had top-of-the-line shingles and underlayment, but poor venting led to warped decking and curled shingles within a decade. Doesn’t matter how good your underlayment is if heat and moisture are trapped up there. I always tell people—think of the roof system as a whole, not just the layers you can see.

One thing people sometimes overlook: even with synthetics, you still need proper overlap and fastening. I’ve seen installs where folks cut corners, thinking the material is bulletproof, but water finds its way in if seams aren’t tight or fasteners are overdriven. And in the Midwest, wind-driven rain is a real test.

I get why underlayment gets so much attention—it’s easy to compare specs and prices, and it feels like a spot where you can “upgrade” without breaking the bank. But honestly, if I had to choose between spending more on underlayment or making sure my attic was vented and insulated right, I’d pick the latter every time. Underlayment is your backup plan; venting and insulation are what keep you from needing that backup as often.

Funny enough, I’ve had a few customers who were shocked when I suggested adding more soffit vents or baffles instead of just selling them premium underlayment. But long-term, that’s what keeps the whole system working.

Underlayment is your backup plan; venting and insulation are what keep you from needing that backup as often.

Couldn’t agree more. I see folks obsess over the “best” underlayment, but if your attic’s a sauna, it’s just a matter of time before problems show up. One thing I’d add—if you’re in an area with wild temp swings, like the Midwest, synthetic underlayments really do hold up better. But even then, if you skip on baffles or block soffits with insulation, you’re kinda sabotaging yourself. Seen it too many times... great materials, but poor airflow and the roof still fails early. The whole system has to work together or you’re just throwing money at the wrong spot.