I get why folks are nervous about overlays, but I’ve seen a few done right that held up just fine—guess it depends on how sketchy the old shingles are. As for the fan, my uncle swears his install actually helped with attic temps, even with two layers. Maybe not textbook, but sometimes you gotta work with what you’ve got... warranties be damned.
As for the fan, my uncle swears his install actually helped with attic temps, even with two layers. Maybe not textbook, but sometimes you gotta work with what you’ve got... warranties be damned.
That’s kind of where I landed too, honestly. My roof’s pushing 18 years and I just couldn’t justify a full tear-off yet, so I did an overlay last summer. Not ideal, but the budget’s tight and the old shingles were mostly flat. I was worried about ventilation with two layers, but after putting in a solar attic fan (the cheap kind from the big box store), I did notice the upstairs stayed a few degrees cooler during our July heat wave. Can’t say if it’s textbook either, but it sure made a difference in comfort.
I’m curious—did your uncle notice any issues with moisture or ice dams after adding the fan? I’ve heard mixed things about how well those fans actually move air when there’s more than one layer of shingles. I haven’t seen any problems yet, but winter’s always the real test around here.
That’s what I was wondering too. I’ve heard some folks say the fans can actually pull conditioned air from the house if the attic’s not sealed up tight, especially with two layers making everything a bit less “breathable.” But then again, my neighbor tried one and swears his ice dam problems got a bit better last winter, so who knows. Maybe it just depends on how leaky your attic floor is—or maybe it’s just luck. Have you noticed any musty smells or anything weird in the attic since you put yours in?
I’ve run into this debate a few times on job sites—some folks swear by solar attic fans, others say they’re more trouble than they’re worth if the attic isn’t sealed up right. Pulling conditioned air from the house is a real risk if there’s any gaps in the attic floor or around light fixtures. I’ve seen it happen in older homes especially, where the insulation isn’t continuous or there’s a bunch of can lights poking through. That can actually make your AC work harder, which kind of defeats the purpose.
On the other hand, I’ve also seen cases where a solar fan helped with ice dams, like your neighbor mentioned. I think that’s mostly because it kept the attic temp closer to outside, so less snow melted and refroze at the eaves. But again, that only really works if you’ve got decent insulation and air sealing between the living space and attic. Otherwise, you’re just moving warm air from the house up into the attic and out the roof.
About musty smells—haven’t noticed anything weird myself, but I always check for damp insulation or signs of condensation after a fan install. Sometimes if you add ventilation without fixing moisture sources (like bathroom vents dumping into the attic), you can actually make things worse. Did you check your soffit vents to make sure they’re clear? I’ve seen people add a fan but forget about blocked soffits, so the fan ends up pulling air from inside instead of outside.
Curious—what kind of insulation do you have up there? And is your attic floor pretty well sealed, or are there obvious gaps? That seems to make all the difference in whether these fans help or hurt.
I’ve managed a few properties where folks insisted on solar attic fans, and honestly, it’s a mixed bag. If your attic floor isn’t sealed tight—think gaps around pipes, can lights, or hatch doors—you’re just sucking cool air out of the house. That’s a real energy waster. But if you’ve got solid insulation and good air sealing, they can help with ice dams and keep things drier up there. I always tell people: check those soffit vents first. Blocked soffits mean the fan pulls from inside, not outside, and that’s where things go sideways.
