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  1. #1
    Chris Hoover's Avatar
    Chris Hoover Guest

    Default Bathroom fan ducting question

    Hey all.

    I'm looking at putting a bathroom fan into a 50's era, single-story house that currently doesn't have one. The options appear to be vent to the roof, or vent through the gable. Being concerned with introducing a leak in the roof, I'm leaning toward the gable vent.

    1) Do I actually have the choice of where to vent? (i.e. if it's the attic and not between floors, am I required to vent to the roof)
    2) If I vent through the gable, am I allowed to run the duct over the joists, or do I need frame something in around the ductwork?

    thank you!

    chris

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  2. #2
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    Default Re: Bathroom fan ducting question

    Quote Originally Posted by Chris Hoover View Post
    Hey all.

    I'm looking at putting a bathroom fan into a 50's era, single-story house that currently doesn't have one. The options appear to be vent to the roof, or vent through the gable. Being concerned with introducing a leak in the roof, I'm leaning toward the gable vent.

    1) Do I actually have the choice of where to vent? (i.e. if it's the attic and not between floors, am I required to vent to the roof)
    2) If I vent through the gable, am I allowed to run the duct over the joists, or do I need frame something in around the ductwork?

    thank you!

    chris
    1)Yes, it is your choice, I prefer the gable

    2) Yes, you are allowed to run the duct over the joust.
    You can also hang the duct from the rafters.
    Note
    Insulate the duct
    Droops or dips in the duct will catch water.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  3. #3
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    Default Re: Bathroom fan ducting question

    Ideally the duct will be galvanized sheet metal and not flexible aluminum or vinyl. It must terminate at a dampered hood at the roof, side wall, or soffit. The shorter the duct run the better it will work. Reference the fan manufacturer's installation instructions, IRC 102.4 and 303.3, if applicable in your area.

    Last edited by Aaron Miller; 08-06-2012 at 01:53 PM. Reason: Typo
    Texas Inspector
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  4. #4
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    Default Re: Bathroom fan ducting question

    Number 3, don't use that cheap plastic duct tape (duck tape) that melts in the heat and allows the pipe to fall back into the attic. Use metal foil tape or screw and clamp everything.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  5. #5
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    Default Re: Bathroom fan ducting question

    Quote Originally Posted by Aaron Miller View Post
    Ideally the duct will be galvanized sheet metal ...
    And support the duct at each section. That will take the weight off of the connection joints, which are not designed to carry the weight of the duct anyway, the joints are intended to be sealed and leak-free, you don't want the joints to pull apart.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
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    Default Re: Bathroom fan ducting question

    Quote Originally Posted by Jerry Peck View Post
    And support the duct at each section. That will take the weight off of the connection joints, which are not designed to carry the weight of the duct anyway, the joints are intended to be sealed and leak-free, you don't want the joints to pull apart.
    10'-0" o.c. as per IRC 1601.3.2?

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  7. #7
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    Default Re: Bathroom fan ducting question

    I can't recall ever seeing a solid metal vent pipe used for a bathroom vent. Not saying it is a bad idea, I just can't recall ever seeing it done. All I see are flex vinyl, flex alum foil vents or Mylar type vent pipes.

    Scott Patterson, ACI
    Spring Hill, TN
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  8. #8
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    Default Re: Bathroom fan ducting question

    Quote Originally Posted by Scott Patterson View Post
    I can't recall ever seeing a solid metal vent pipe used for a bathroom vent. Not saying it is a bad idea, I just can't recall ever seeing it done. All I see are flex vinyl, flex alum foil vents or Mylar type vent pipes.
    Same here

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  9. #9
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    Default Re: Bathroom fan ducting question

    The flexible vinyl ducts trap dust and go moldy. I'll post some pics.

    Here's a pipe full of crud that blew off as well. Actually, it looks like somebody covered the fan purposely. Whatever.

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    Last edited by John Kogel; 08-09-2012 at 04:13 PM.
    John Kogel, RHI, BC HI Lic #47455
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  10. #10
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    Default Re: Bathroom fan ducting question

    Quote Originally Posted by Scott Patterson View Post
    I can't recall ever seeing a solid metal vent pipe used for a bathroom vent. Not saying it is a bad idea, I just can't recall ever seeing it done. All I see are flex vinyl, flex alum foil vents or Mylar type vent pipes.
    The production builders here put in whatever they find on the truck. The better builders install only sheet metal. Some of the AHJs require sheet metal. Most don't know the difference.

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  11. #11
    Chris Hoover's Avatar
    Chris Hoover Guest

    Default Re: Bathroom fan ducting question

    Thank you all so much for your input. I really appreciate it!

    Chris


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