Bathroom vent into a chimney?

Discussion in 'Remodel Forum & Blog' started by smartin684, Jan 29, 2007.

  1. smartin684

    smartin684 New Member

    May 3, 2005
    I have a 2nd floor gutted batheroom,ready for remodel. I need to install the vent fan, but the joist run to the side of the house where it will be a real pain to work on the outside on a ladder. There is an old, unused chimney stack running through the bathroom and someone had at one time run a vent from a gas space heater into the chimney stack. So I have this great vent opening just waiting for me to take a shortcut. My question is.... can I run my bathroom vent into this unused chimney stack? What would be the possible downside to attaching my bathroom vent to this opening? Like I said, the chimney is not used by anything anymore.
  2. leejosepho

    leejosepho DIY scratch-pad engineer

    Nov 23, 2006
    disabled-retired industrial fabricator
    200 miles south of Little Rock
    Condensation is the only thing that comes to mind for me here, and that would preclude you from running a flexible vent line (like the "liner" my furnace uses) all the way to the top of the chimney. Long runs or vertical rises can cause the same kind of problem for dryer vents. But, I cannot see any reason to not run your new bathroom vent into an old chimney.
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  4. Gencon

    Gencon Renovator

    Nov 16, 2006
    Etobicoke, Canada
    It can be done. Use ridgid pipe, nothing flexible. Insulate the pipe with a sleeved insulation. This insulation has a plastic vapour barrier over it. The insulation must be continuous from the termination point to 5' inside the building envelope. The duct must be sealed as well as the VB and where it comes through the wall. You may want to upgrade to a minimum 150 cfm fan if the exhaust duct run is greater than 12'. Don't forget to use a termination cap that has a built in backdraft damper and ensure that the top of the chimney is sealed tightly.
    Running the fan a bit longer will ensure that any condensation that may form within the pipe gets dried up. A timer control works great for this.Just press the 30 minute button as you leave the bathroom after a shower.
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