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bathroom fan questions galore

16 years ago

In tenant's apt. we have 6 x 10 bathroom ( w/ 9 foot ceiling). Previous tenant took showers daily which created mold problem and some damage to painted wood trim around window which is adjacent to shower. Hoping installing exhaust fan will keep it dry. Have been searching this forum and internet in general and still could use some help w these questions:

What size? Is 80 cfm adequate or too much? Would like to err on the side of too much power... but I understand there is such a thing as too much suction. The duct will be only about 5 feet long and a straight shot to the outside.

Any advantage to motion sensor vs. humidity detector models? If I get one of these does that eliminate the need for wiring for a switch altogether? (there are lights on the wall so no overhead lite is needed). We need to make sure this fan is used and not give tenant a choice about whether to use it or not -- so the switch model is out.

Any models you can recommend? It would need to have a 3" duct and not a 4" due to situation with having to bore a hole in brick exterior.

t. i. a.!!!!

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Comments (8)

Debbie Downer
Original Author
16 years ago
More questions.

Are the "quiet" models like the Panasonic whisper line also quiet OUTSIDE the house as well as inside? I like quiet (what little there is in my neighborhood) and don't want to contribute to NOISE POLLUTION. It concerns me that their motion detector fan runs continuously but kicks up into higher power when motion is detected. However, this might not be so bad if it is truly quiet.

BTW, whos got humidistat fans? Keep hearing reference to these but have yet to find one online.

THANKS
Debbie Downer
Original Author
16 years ago
hellloooooooooooooooo
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MongoCT
16 years ago
With existing mold and the higher ceiling, I'd opt for a Panasonic 110cfm.

Do not choke the duct down to 3". Run a 4" duct, then transition to an outlet that will fit the physical dimensions you need (3" height max) but will not limit the airflow. Meaning that your outlet will have a 4" round to accept the 4" duct from the fan, but the exit hole out of your house might be 3" tall by 5" wide.

They do have outlets that are literally the size of a standard brick for just this purpose.

I usually put fans on timer switches. I use ones by EFI.

EFI has motion sensing switches. This one will turn the shower fan/light on when someone enters the area, and you can set it to stay on for up to 30 minutes after the person has left the room.

The Panny Whisper fans are quiet. To maintain the quietness, use rigid 4" metal duct instead of the cheap flex duct, and have no abrupt turns in the duct within 2'-3' of the fan.

Flex duct (unless just using a short section of it to isolate the fan from the duct) or turns in rigid duct too close to the fan will create the dreaded air turbulence noise and minimize air movement out of the bath.

Mongo
spanky67
16 years ago
Hey, I thought I was the only one to use EFI switches. I guess living in CT and having The Taunton Press just up the road in Newtown has its advantages :)
MongoCT
16 years ago
Greetings Spanky, I always use EFI. Usually the timer switches, only once in a while the motion.

Ever visit Taunton? Good guys, I'm beer buddies with a couple of the editors over there.

Mongo
Debbie Downer
Original Author
16 years ago
Mongo, thank u! that helps...

question about using running a higher powered fan in a small space. elsewhere on this forum I read that with door closed that creates an air situation which causes the fan to run louder. My question is - does that damage the fan?

You suggested round metal duct but would PVC pipe be any better or worse? Happen to have a piece of that lying around....
MongoCT
16 years ago
No, the fan won't be damaged. These fans are usually squirrel cage fans. No harm no foul.

PVC would be okay, but I'd recommend 4" Schedule 40. I wouldn't use thin wall septic pipe. Use aluminum tape (2" roll of peel and stick) to seal the transitions.

4" metal duct is pretty inexpensive, but the Sched 40 would be okay.

Mongo
luckyparker
16 years ago
Strength/power?

How much does the power on these fans vary? How do you determine how strong a fan you need?

BTW, if your bathroom is in a guest area, consider a not-so-quiet model. You may appreciate NOT hearing some things.

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