Bathroom Exhaust Vent Size?

Discussion in 'Remodel Forum & Blog' started by CTWeekendWarrior, Sep 30, 2008.

  1. CTWeekendWarrior

    CTWeekendWarrior New Member

    Jul 8, 2008
    Structural Engineer
    Enfield, CT
    My question is regarding a bathroom exhaust vent for a new bathroom I am adding to my home. The volume of the new bathroom is approx. 500 cu ft. (11 ft w X 6 ft D X7.5 ft H). The fan in my other bathroom does a poor job of exhausting steam from the bathroom, and condensation on the walls is a problem. Does anyone know if there is a guideline as far as the recommended fan capacity per square foot of room volume? Thanks for the input!
  2. geniescience

    geniescience Homeowner

    Nov 27, 2005
    humid summers hot, humid winters cold
    I got an in-line centrifuge ("squirrel cage") from Broan or Nutone a few years ago. 200CFM capacity. We like it. It is quiet and powerful. In the other bathroom we bought a fan that had motor blades, and it makes an irritating noise. It was 120 CFM. FWIW, I'd put my money on a squirrel cage any day.

    No matter what, steam still fogs mirrors when the shower has run, but you can see the level of the fog line rising every minute as the fan keeps pulling air out.

    The more powerful the ventilation, the more you have to plan for make-up air to come from somewhere else.

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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    I think construction standards call for 6 air changes per hour. So for example, a 6 X 12 room, 8'ceiling = 576 cubic feet, X 6 changes = 3456 cuft per hour, divide by 60 = 57 CFM. Now, I personally feel that is minimal, and would like to see more like 8+ changes. And a round number of 1 CFM per sqft is what I choose.
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