View Poll Results: Best way to vent these bathrooms

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  • Shorter duct through ROOF (NJ Weather)

    1 100.00%
  • Longer duct through GABLE wall (NJ Weather)

    0 0%
Results 1 to 5 of 5
  1. #1

    Question Need advice on bath ventilation (Long run thru gable, or short run thru roof?)


    I'm not sure if this is the best place to ask this question, but regarding bathroom exhaust fans, I understand I they are best to duct:

    1) Preferably to the gable (with the pipe angled slightly downward outside?)
    2) Short duct runs (insulated duct?)

    However, since I have the 2 bathrooms upstairs in the center of the typical 4-bedroom "New Jersey 1970s colonial", I can only do one of the above. The question is, which option is better?

    Is it better to "short-run" pipe the bath exhaust through the "roof"? or is it better to "long-run" it to a "gable vent" on the side of the house?

    Here is a picture: The two bathrooms are where you see the two inner upstairs windows:
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    I seem to be getting conflicting information from different contractors...I'd really like to know what you guys think. Thanks so much!


  2. #2
    Join Date
    Jul 2011
    East coast USA
    shorter the better.

    there is a limit depending on the size of the fan, its ability to push air through a duct. So if you choose to go long your fan needs to be sized right in order to push the air through the duct to the outside.

    But again shorter the better, easy to clean ducts, long ducts will build up of lint. If you use metal duct you can have moisture sit in the duct and rust.

  3. #3
    Join Date
    Oct 2010
    Anderson, South Carolina, United States

  4. #4


    Thank you so much, guys! The fan is nothing overly powerful (NuTone 9093 70-CFM), so it makes sense what you're saying about opting for the shorter run.

    To tackle the issues I've heard about venting the bath exhaust thru the roof, here's what this contractor proposes:

    1) Preventing Ice Damming
    I've heard to avoid the roof, if possible, since it can cause ice damming here in New Jersey. This contractor's solution was that he would use 4-inch "flex-tube" (or solid aluminum) to position the roof vent further back away from the gutter (3-4 feet of duct).

    2) Flex Tube vs. Solid Aluminum
    Since flex tube has ridges (which I thought I read was not recommended either since it impedes airflow), the contractor said he can use solid aluminum, but would be another $25-$30 in hardware. (I don't mind the extra few bucks obviously, as long as it's the best course of action!)

    3) Using insulated ducts (or adding insulation around the ducts)
    The other thing he said he could do is use insulated ducting (or add insulation) to prevent condensation issues as it travels thru the attic.

    Hoping you think the above sounds kosher(??)
    ...but if not, I'm certainly open to different methods and ideas as well. The contractor, although confident, also seems to be very open-minded as well--a good mix.

    Thanks again

  5. #5
    Join Date
    Oct 2010
    Anderson, South Carolina, United States
    Rigid aluminum and insulated. I haven't ever had to deal with ice damming down here in the southeast so I'm not sure about that but his recommendation sounds plausible.

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