Bathroom fan vent path when joists are parallel to wall?

Discussion in 'Shower & Bathtub Forum & Blog' started by DiyDave, Mar 28, 2013.

  1. DiyDave

    DiyDave New Member

    Messages:
    3
    Location:
    Florida
    I ordered a panasonic bathroom fan and the ceiling joists run parallel to the gable wall I'm exiting out of so I'd have to curve the vent up slightly to get over the joists. Is that initial up pitch to get over the joist going to cause a possible condensation issue inside the vent or will I be OK? The only other option would be to exit out the bottom of a soffit and I read that isn't a good idea. Thoughts?
  2. ForkWheelDrive

    ForkWheelDrive DIYer / Mech Engineer

    Messages:
    12
    Location:
    Fork, MD
    I installed a bathroom vent fan in a similar situation. The duct runs through the joist space about 5' then elbows up into an attic area (its a 1 1/2 story home where the second floor has dormered ceilings, so thats why there is attic space on the second floor). Once it elbows up and over the joists it runs over a couple feet to the exterior wall. Seems to be working well. I'm not exactly what you mean by condensation, or what would cause that. I would think the CFMs from the fan would keep the moist air flowing out before it condensed on the duct.
  3. DiyDave

    DiyDave New Member

    Messages:
    3
    Location:
    Florida
    From what I understand the concern is that if the area is really steamy there is a potential for steam to condense at the top of where it makes the upward turn and slide down. I think I agree with you though that the fan cfm should probably keep things running through as long as I don't make the bend too sharp.
  4. jadziedzic

    jadziedzic Member

    Messages:
    96
    Location:
    New Hampshire
    Two suggestions: use rigid metal duct, not the flexible crap, and use a goodly amount of high-quality insulation around the metal duct (the metal foil/bubble stuff seems to have the best R value per inch of thickness).
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