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Thread: Bathroom Vent Leaving Building

  1. #1
    DIY Senior Member molo's Avatar
    Join Date
    Sep 2006
    cold new york

    Default Bathroom Vent Leaving Building

    Hello All,

    I have a building where there is a bad moisture problem. There is mold/mildew that grows on the ceilings/windows in the winter time. There are two causes for this; 1. Wet Basement (foundation may need to be excavated, and/or interior footer drains installed), and 2. No vent in the bathrooms. I had a plumbing/heating company give me an estimate to install bathroom vents. It is a ranch home with a very small attic space. The guy gave told me he would run the vents out so that they came out of the bottom of the soffit.

    Question: Will running the vents out of the bottom of the soffit cause the moisture to over time soften and rot the soffit out? Would it be a better idea to run the vent out the roof?


  2. #2


    I know my bathroom is vented this way. I think I have even seen it as an option on exhaust fan boxes. Seems like it's fine as long as your soffit is not blocked up with insulation etc.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Do it right, either run it out the roof, or the sidewall. Running it into the soffit is a hack - you want the moisture out of the house, not stuck anywhere in it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014


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