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  1. #1
    Join Date
    Aug 2011
    Posts
    2

    Question Bathroom ventilation fan

    I am having problems with my upstairs bathroom ventilation fan during showers. The house is 8 years old and originally came with a 50 CFM fan. We were having problems with moisture on the walls/mirror with the OEM fan, so we switched to an 80 CFM fan, but to no avail, still moisture on the walls and mirror. Problem now is starting to show mildew and mold on wood trim around shower. The bathroom is only 8' x 5' x 8', so 50 CFM should pull the moisture out, but it did not do the job, hence the change. We are having no problems with moisture in our master bathroom, which is right next to problem bathroom.

    Any suggestions on what to look for or change with the ventilation fan?

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    6,736

    Default Re: Bathroom ventilation fan

    Maybe it's not the fan size, but the vent duct itself?

    Here's a test you can do: run the vent and go to where it comes out of the building. Do you feel a draft? weak? strong?

  3. #3
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,969

    Default Re: Bathroom ventilation fan

    A puff of baby powder or a smoldering cigarette will tell you if you are getting good draw too. Do check both ends of the vent pipe.

  4. #4
    Join Date
    Aug 2011
    Posts
    2

    Default Re: Bathroom ventilation fan

    Did the smoke test under the fan, and the fan pulls the smoke with no problem. I will have to get up in the attic later to check on the vent duct from the the fan to the roof.

  5. #5
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,663

    Default Re: Bathroom ventilation fan

    Maybe there isn't enough air coming INTO the bathroom to replace what the fan is attempting to exhaust? You should have a gap of at least 3/4" at the bottom of the door.

    Even if you have a sufficient gap, your house may be too airtight, especially if it was built in the late 70's thru the 80's. If you have a forced-air heating system, installing a fresh air duct from the outside into the return air plenum may provide sufficient replacement air.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  6. #6
    Join Date
    Sep 2011
    Posts
    1

    Default Re: Bathroom ventilation fan

    There must be proper ventilation in the bathroom when you are having a fun because it needs the air go out otherwise it cause suffocation thats why ventilation fan doesnt work

  7. #7
    Join Date
    Aug 2011
    Posts
    14

    Default Re: Bathroom ventilation fan

    Quote Originally Posted by Fencepost View Post
    Maybe there isn't enough air coming INTO the bathroom to replace what the fan is attempting to exhaust? You should have a gap of at least 3/4" at the bottom of the door.

    Even if you have a sufficient gap, your house may be too airtight, especially if it was built in the late 70's thru the 80's. If you have a forced-air heating system, installing a fresh air duct from the outside into the return air plenum may provide sufficient replacement air.
    That would be my guess, too. Is it better if you crack the door? Or maybe it's pulling air from an adjacent door and not circulating in the room well enough?

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