We are having our entire roof replaced because of hail damage. The current roof has two powered fans plus a ridge vent. The roofer says that only one is recommended and wants to just put in the fans. It seems to me that the passive vent system would be far superior, and also relatively expensive. Not surprisingly, they are not reducing their bid, but just keeping the extra money. I think I am not getting a good deal on this.
I’d think that the fans would be much more expensive to install than the passive vent. If I recall correctly, putting in the ridge vent means maintaining a small gap at the ridge, then installing maybe $200 of ridge cap material then the shingles you were already installing. The fans take a lot more work, electricity, cutting the holes, installing them, flashing them, etc.
Anyway, having both seems to be a terrible idea, the fans will pull air from the ridge vent and not properly vent the space.
I was looking at the figures from the claims form. Redoing the vent seems about 5 times as expensive. Two fans are currently installed, so there is essentially no installation costs for them.
Homeowner, not a contactor: My old house had a ridge vent and AFAIK worked fine.
My current house came with 2 fans, neither of which worked when I moved in 10 years ago. I replaced both motors then and adjusted the thermostats, which got things working OK for a couple years. Then one of the new motors died; replaced that one again. Now the other has stopped running but I haven’t gone into the attic to sort that out. At least the holes the fans sit in provide ventilation even when they don’t run…
Unless I had a really good reason otherwise, when I redo my roof it will get a ridge vent.
Passive venting is minimally effective in hot summers. Combining eave and/or ridge vents with a fan doesn’t is a small improvement but may not provide any extra air movement across a large or unusually shaped attic. That may be why there were two fans there. If your winters are dry no vents and a large fan may be the most economical solution because the fan will draw air from the house below and reduce cooling costs in summertime. The only thing to totally avoid is no vents or fans at all.
Personal anecdote. We have both a ridge vent and a power vent in the attic. I had the power to the vent shut off while doing some work, and forgot to turn it back on. During one hot afternoon, the smoke detector began to chirp. When we checked, we discovered the ceiling and upper walls were hot and condensation had formed on them (which affected the smoke detector.)
TLDR: Here in the hot, humid Midwest, the ridge vent by itself isn’t effective.
My understanding is that roof vents are effective circulators by drawing outside air in through openings at attic floor level and letting the hot air rise and exit thru the roof vent. But if the attic floor (eave/soffit) vents are blocked, there is no air circulation, and the roof exhaust vents are pretty ineffective.
And it’s not uncommon for these intake vents to be blocked. Especially if someone (like a Do-It-Yourself homeowner) has added loose fill insulation into their attic, without making sure these intake vents are kept clear. It seems to work great through the winter, reducing their heating cost. But when summer comes, the blocked attic intake vents prevents air circulation, and their summer air conditioning bill goes way up.
As long as they’re up there replacing your whole roof, have them check the intake vents. Maybe add some more, to ensure air circulation in your attic.
Ridge vents are preferred. Always moving air; always working. Fans work at a given temp, and then the rest of the year you got stale air… and stale air ain’t good air for wood framing, or anything.
.
This is spot on. Ridge vents can move a surprising amount of air, but they rely on the soffit vents being clear of obstructions and attic detritus not getting in the way of the air flow. Ridge vents can also sometimes get clogged up with dirt and dead bugs and whatnot and may need to be periodically cleaned.
The main takeaway is: in the winter you want your roof to be cold. In the summer you want your roof to not bake so much. If you can pull that off, you’re generally OK.
friedo beat me to it.
You also need soffit vents to keep air moving. If the roof is being replaced, the OP may already have soffit vents.
Gable vents (instead of ridge/roof vents) are also an option. Depends on the roof/climate and other things.