Attic fans - best spot to mount ?

Ron Jr._3

Was curious if there's any advantage of having an attic fan gable vented instead of roof vented ?  House has 2 gable vents and the existing roof vent fan went kaput . Instead of replacing the fan right in the roof vent the contractor mounted a new one in a gable . Told the homeowner it was a better spot . I'm doubtful since it's drawing fresh air in from one gable vent now instead of 2 .



Thanks in advance !

Steamhead

Depends

on how the roof vent was mounted. If it wasn't located where it could pull air thru the entire attic by drawing from the two gables, then the fan at the end is better. You want airflow thru the entire space.



But a gravity circulation system, drawing air from under the soffits and letting it exit at the gables, works well too and doesn't use any power. That's what I have. You can see the soffit grilles in the pic.

Patrick_North

Plug that hole

I'll go along with the gable being a better position in this case, but if the roof vent is still in place it should be plugged so as not to short circuit the flow of air across the entire attic space. The fewer (giant) holes in ones roof the better, I think it's fair to say, for several reasons.

Good luck,

Patrick

Ron Jr._3

Thanks guys .

I was asking this question for my girl , who lives in a 2nd floor apt in a Levitt ranch house . Here's a pic of where they took the old fan out and where they mounted the new one . The old roof mounted fan was right in the middle of the attic . I was thinking being situated there it would draw air in equally from both gable vents as well as the soffit vents .



The new fan pushes 5 times more air than that vent can handle ( downloaded the .pdf ) . And they mounted it on the existing 2 by 4s that hold it off the outer plywood sheething . More air is blowing back in the attic than going out . The fan is mounted right above Tam's bedroom . It sounds like a Leer sitting on a runway waiting to take off  . For hours . Did I mention there's no shut off switch ? Just the temp dial on the fan and the circuit breaker .



I needed an unbiased opinion cause I have a history with this contractor . Didn't know till after the install who did it , but later found out he's an ex of my ex and we ain't exactly friendly to this day .  Always runnin' into someone ya' know in good ol' Levittown !  

Patrick_North

Egg on my face...

I retract my earlier post- I didn't read your question very carefully. I thought there was originally only one gable vent. Yes, this is worse. This is only "better" for the installer who didn't need to climb out on the roof to replace the fan! This is a hack job, and I would say you're due a fix at least. The exhaust outlet can be enlarged with little work and a new (larger) louvered hatch- quite inexpensive- can be installed easily from the inside if need be. As you noted, the fan needs to be mounted so that its not simply recirculating hot air within the attic. And if the fan CFM exceeds the available inlet CFM, well, there could be additional problems- the least of which may be early fan mortality. If it's on a dedicated circuit, I'd shut the thing down until it was fixed, if it was my place.

Good luck,

Patrick