Maximum length of duct for bathroom fan

Discussion in 'Shower & bathtub Forum & Blog' started by Douche, Apr 13, 2006.

  1. Douche

    Douche New Member

    Messages:
    9
    Location:
    Delaware
    I have a small bathroom (less than 80 sq feet). I am installing an exhaust fan on the ceiling in my upstairs bathroom. I prefer to vent the duct out the attic wall rather than the roof. The wall is approximately 15 feet from the location of the exhaust fan. My question is there a maximum duct work distance or is there a certain cfm fan or fan speed I need to blow open the vent at 15 feet? I plan on using flexible metal duct.

    Thanks!
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    There is no regulation on this. 15 feet is not excessive. Based on 6 air changes per hour, a 70 CFM fan would be "adequate". I always prefer to use 100 or 110 CFM even for a small room like your. This will minimize any problems with mold and mildew. Spend the extra $$$ and get a unit with a maximum sone rating of 1.0 You will live with the noise of this fan for many years, so it is worth a few bucks to go quiet.
  3. Douche

    Douche New Member

    Messages:
    9
    Location:
    Delaware
    Many thanks..appreciate the advice!!!
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