Bathroom Exhaust Fan Leaks Cold Air

7 responses

  1. Trish
    November 23, 2013

    Hi, We have water leaking through our bathroom vent only when it is cold outside. We do not take showers in this bathroom. The voting pipe goes straight up from the bathroom then approx. 16ft throughout the attic to the roof. We have completely insulated the pipe. It is still leaking like crazy through into the bathroom and now there is water leaking into the kitchen but only when it is cold outside. Our kitchen ceiling is now covered with wet splotches. What do we do now??

    • TIm Williams
      February 6, 2015

      The water is almost certainly condensation - this means that warmer, more humid air (i.e. the air inside your house) is escaping through this exhaust vent.

      Hot air rises, so your home's warmest, most humid air is always up at ceiling level, seeking a way to get even higher. It'll use any crack it can find... and apparently your exhaust vent pipe is a nice open highway for air that wants to escape.

      As it goes, up, it cools and the water condenses on the inner sides of the pipe and makes its way back down.

      Basically, you've re-invented a distillation still, only instead of making moonshine you're making ceillng water 😉

      Your base problem is that air can escape the house via that vent too easily. It sounds like the pipe has nothing to act as a damper/flapper. That's why these dampers exist; to make sure the pipe is "closed when not in use".

      Fix the air escape by installing either an internal or rooftop damper.

  2. Jean
    October 12, 2014

    Tim. We just bought this home and have a gas fireplace . When it is windy out the vent has something outside that bangs. Hope you can help.. Jean

    • Tim Carter
      October 15, 2014

      Yes, I can help. Get up and see what parts are banging and fix them.

    • Dean
      November 10, 2016

      Get up the roof, bring some neoprene screws from Lowe's.

  3. frank
    February 7, 2016

    The damper on the bathroom fan broke off, do i replace the whole fan or is there a way to fix this piece (damper)

  4. John
    February 10, 2017

    My house has a bathroom fan duct that was installed to point toward an eave vent to let the exhaust air out. The fan seems to clear air from the room, but outside air can seep in when it is not running, e.g. cold air seeping in in the winter. The fan is a good Panasonic one, with louvers by motor in the bathroom ceiling. I'd like to have an outside louver installed at the eave vent, but the standard outside louvers are 6" on a side, and the eave vent is only 3-1/2" to 4" tall, so the standard is too big. Is there a smaller outside louver that would fit, or else what do you recommend?

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