Are quiet bathroom fans really quiet or is it my installation?

[# Fred #]

Wife purchased three of the quiet Broan QT080L bathroom exhaust fans with light and night light. I tested it out on the kitchen table and it was quiet so then I proceeded with the installation in the downstairs 1/2 bathroom. The bathroom is down to studs and subfloor with all insulation removed for remodel. The Broan has a 4" duct connection but the house has 3". Once everything was connected, the fan wasn't all that quiet. The noise was from both fan vibration and wind. Its still more quiet than the old noisy fan but I could hear the new fan from upstairs. The mounting is solid to joist per instruction and the connection to the 3" duct is tight. I suppose once I close up the ceiling and walls with insulation it would not be as bad. Are quiet fans really all that quite? Maybe should have purchased Panasonic fans instead - its the same price.

[BobK207]

The ultra

[BobK207]

I was unable to find the specs for the model you metntioned

QT080L

maybe a letter is missing from the model number?

in any case..........one of the design features of the quieter fans is the use a a larger duct size.

The quiet ones use a 4" duct & the really quiet ones use a 6" duct....to keep the air velocities & the back pressure on the fan low.

By using the exisitng smaller duct you are negating some of the quiet fan's benefit.

Addtioning most of the quiet fans have some sort of resiliant mounting system...does yours have that & is it working?.....hard mounting allows more sound to be transmitted through the framing.

cheers Bob

[bamboo]

My panasonic uses an 8" duct, a little pricey compared to the box store stuff but very well made. About 150$

[dpb]

I expect Bob has already hit on the two prime areas --

Might just try it by disconnecting its outlet from the 3" ductwork temporarily and see if the noise is reduced. I'm guessing it will be and to get the benefits of the fan you'll need to install larger duct. Don't see could go wrong in going to 6" even although probably no real advantage as the outlet is 4". In doing so, though, avoid the flexible ribbed wall stuff as the rough surface adds to turbulence which raises noise. If you absolutely need some for a connection, make it as short as possible. And, of course, make sure the ductwork is mounted securely so it doesn't add its own vibration.

If, otoh, what you then hear is actually the fan itself running and not airflow, I'd look at adding some dampening between it and the joists. A section of tire sidewall is one of my favorite things to use for such isolators.

Finally, if you do add insulation or other sound-deadening around it, be sure to not block any necessary air circulation for cooling of motor and lights, if any. Don't want a quiet installation to become a fire hazard! :)

[Joseph Meehan]

I suggest that is your answer. Dropping the size of the exhaust increases the noise. You also increase the noise the smaller the room. It sounds louder.

[Mortimer Schnerd, RN]

Why would you want a quiet fan? Frankly, I prefer a fan to make a bit of noise to cover up any other extraneous sounds that may escape.

[Kurt Ullman]

You are SOOO Bad, MS

[naked on the phone]

none of that matters, it all depends on what you are sticking in the fan

depends on how bad the farts are

you're wife bought the fan? in that case I would say.. this is her way of telling you how rotten you smell

like.. something crawled up inside you and died jack

[# Fred #]

Sorry, typo on my part: its QTR080L

No.

The second floor is above this bathroom. The existing 3" duct runs along the joists and punch out on one of the outside walls. The 3" duct has a 25' run and its the flexible kind so more air restriction. There are blockings between the joists and seems not possible to upgrade to 4" ducts without tearing out the family room ceiling. Bathroom is small so I don't need a lot of CFM - perhaps I could reduce the motor speed.

.....hard mounting allows

[# Fred #]

The Broan cost us a little more than that at the local hardware store but in retrospect the Panasonic may have been a better choice.

Did you upgrade to 8" ducts too?

[avid_hiker]

For sure......that loud "PLOP" in the water.........or that loud ECHO of gas back fire. The louder the fan......the better.

[HerHusband]

I am not familiar with the Broan fans, but we installed a few Panasonic fans in our house. They're the type with the large squirrel cage style impellers.

The smaller (70cfm) fans are virtually silent in operation. We have one that runs continously as part of our house ventilation system, and unless you are standing directly under it and the house is completely silent, you can't hear them running at all.

We have one larger (110cfm?) Panasonic fan in our master bath, and while it is louder than the smaller fans, it's only loud enough that you can tell it's running. It is still MUCH quieter than the fans we had in our previous house.

In our case, we have 4" ducting. Two fans are close to the exterior walls, so I have flexible ducting connecting the fan to the wall vent. One of the fans is in the center of the house, so I installed rigid PVC piping on the long straight runs to minimize turbulence. It only uses flexible ducting at each end to connect the fan and wall vents.

Your fan would most likely be quieter in your test because it's not transmitting sound through the framing, and there's no restriction on the air flow. Reducing to the smaller duct size will make the fan work harder and increase noise from the air turbulence. If there's no kind of rubber isolation in the fan, any vibration will probably transmit through the ceiling framing and make it sound even louder. Another possibility is you may have knocked a balance weight out of position or off entirely?

Anthony