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Old 01-20-2011, 05:02 PM   #1
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Best practice question - Exhausting bathrooms fans in new construction.

Hello, I have GC'd the build on our house and I'm a bit stumped, or it's possibe that I don't want to hear the best answer to my question. Our house has 3.5 bathrooms 3 of which are on the 2nd floor with the .5 being a powder room on the 1st floor. All fan exhausts are currently ducted using gvalvanized metal duct to the attic and are waiting to be vented to the outside. This is where the confusion sets in. Should I bring them all together into a single stack vented to the outside, taking cfms of each fan into consideration for sizing or should I vent each fan to the outside independantly? Should the venting to the outside be done vertically through the roof or out a gable end?


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Old 01-20-2011, 05:34 PM   #2
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Something to think about.

I would consider this. Your attic should be vented well enough to consider it as being outside. If not, we should be talking about this. I would not go through the roof just for a bathroom vent. If they are not all in the same area, connecting them all together could cause more problems than it is worth.

If this air contains lots of moisture, than you will have to vent it outside. And, this would have to be a ton of moisture, like what comes from a dryer.

Head for the gable if possible. Good luck!


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Old 01-20-2011, 07:17 PM   #3
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Instead of separate fans, I would consider a remote unit that allows all of the ducts to come from the bathrooms, and then exit out of the single duct like you want. The unit I am talking about is the same as used in commercial installs, but it would never be heard in the baths, and would only come on when the room is occupied.

Last edited by gregzoll; 01-20-2011 at 07:29 PM.
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Old 01-20-2011, 07:37 PM   #4
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Depending on where you are located you may not have to vent the powder room at all as many jurisdictions do not consider a 1/2 bath as a room that produces moisture (go figure).
Also depending on where you're located you may be required to have a small vent fan that continuously runs sized depending on the sq. ft. of your house.
One of the bathroom fans can be used for this.
I am just a font of knowledge ain't I?

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Old 01-20-2011, 07:39 PM   #5
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Venting it to the outside is the only RIGHT way to do it.
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Old 01-21-2011, 06:26 AM   #6
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rbartram - I'm in an almost identical situation. 1/2 bath on the first floor, and a jack and jill setup on the second, requiring three fans. I'm doing everything I can to get them out a gable. Personally, I Hate roof penetrations. Especially in this case, as the pitch is only 3.75/12.

Gregzoll - That's a great idea. And at first glance, may even be cheaper to install. Trying to find low noise fans seeems to be pricey.


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