Venting two bath exhaust fans

Old 10-24-02, 10:04 AM
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Venting two bath exhaust fans

I have two bathroom exhaust fans that are presently venting only to the attic. I have a few questions concerning properly venting them to the outside.

Unless I go vertical (prefer not to to avoid roof penetration--but could be persuaded to --it is a ranch with a low sloping roof. A vertical run would be 4-5 ft.. Plus in a month or two will have snow on roof in central NY) the horizontal runs might be 10-15 ft. Both enter into attic approx 5-6 ft apart.

Is 10-15 ft too long?

Is there some way to connect these together in the attic and have just one vent to the outside? How so?

Is it preferable to exit at gable end of house, rather than under eaves where the exhausted air (must be very tired by this time - ha ha) could re-enter attic thru the eave vents?

Any reasons in favor or against using pvc pipe rather than smooth metal. Might be easier for me to work with and provide some sound dampening and insulation?

Any responses and insight are appreciated. Thanks!
Old 10-25-02, 04:37 AM
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I live in Minnesota and I agree with you that it is not a god idea to go thru roof because of snow issue. At 10' to 15' to a gable, probably have too far to go for the little fans.

I had the same problem in my house ( 20' to gable). I ducted off the fan, immediately transitioned up to 6", and ran to the gable. Just before I went out the gable, I installed an in-line fan and wired it with the bath fan. Works great! In your case, I don't know that you would be able to connect both fans to a single duct if you use my idea of an in-line fan at the gable. The problem would be in switching the in-line fan to come on from two different locations without also turning on both bath fans.

Hope this helps.

Old 10-26-02, 01:55 PM
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I combined both ducts together thru a Wye and connected to a roof vent with a cap. Of course, I live in CA and there's no need to worry about snow.

Joining two vent ducts together is not a problem; problem is to find a best way to exit from your house.

If you don't wanna install a roof vent, I'll say to vent it thru a soffit. It's a less distance than to the gable vent.
Using an inline fan, although it's quite unorthodox, is not a bad idea. Previous thread mentioned about a conflict with switching the inline fan. The possible solution, if you choose this route, will be to install 2 separate inline fans, one per duct, right before 2 ducts enter the Wye to be joined together. You can wire them separately to each switch in bathrooms.

This booster fan may compensate for the loss of thrust due to a long run to the gable vent.

Venting thru a soffit vent sounds like the easiest idea in my opinion.
Old 10-29-02, 07:54 AM
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dave houlihan,

These might be good to look at but bear in mind the first one is expensive but works great when you are talking about distances and there would be no concern about snow if done properly.

Good Luck!

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