But for those who’ve had both, does felt hold up any better if your venting isn’t perfect, or does it fail just as fast?
Honestly, I’ve seen both types take a beating when attic ventilation’s not right. Synthetic’s supposed to be tougher, but like you said, it’ll curl up and look sad if the heat’s trapped up there. Felt, on the other hand, just kind of dries out and gets brittle. I had a spot above a bathroom where the vent fan wasn’t hooked up right—felt underlayment basically turned into a potato chip after a couple summers. Not pretty.
I wouldn’t say felt “holds up” better, but it might fail differently. Synthetic tends to peel and let water sneak in, while felt just sort of disintegrates. Either way, without good airflow, both are gonna have a rough time. Midwest summers can cook an attic like a slow-cooker, so venting’s probably more important than underlayment type.
Curious if anyone’s tried those fancy “breathable” synthetics? I keep hearing about them but haven’t seen one in the wild yet...
