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bath fan, shed roof, cold air coming in

nctacoma | Posted in General Discussion on November 6, 2009 02:55am

I have a shed roof bathroom. The panasonic vent fan in mounted in the shed roof 2×12 rafters.
It is allowing an incredible amount of cold air into the bathroom.

Any remedies? I believe the fan is vented directly outside into a roof cap with a flapper on it.

Reply

Replies

  1. cjeffrey | Nov 06, 2009 04:07am | #1

    You may have to pull down the van. It may have an uninsulated pipe leading to the roof vent. and be a fairly direct path. You may need to use a insulated pipe and run longer on the horizontal. Not straight up.

    I prefer to put the bath vent fan on an interior wall. Run it down the wall and out the floor joists. Cold air can not rise like that and come in the fan.

    I know they make a flapper for dryers that has a Styrofoam ball in it, maybe something similar for a roof application? Ask around.



    Edited 11/5/2009 8:09 pm ET by cjeffrey

  2. rnsykes | Nov 06, 2009 04:28am | #2

    Is the damper stuck open? Or missing? There should be a damper at the fan, and then another one at the roof cap. Either one could be stuck, and the one at the fan is easy to knock out when you install the duct.

    1. wane | Nov 06, 2009 04:18pm | #3

      okay, the panasonic fans do not have a complete damper, it is clipped to allow air to pass through, ..

      similarly most exhaust vents are the same ..

      if you call them to ask why they say to keep them from freezing up ..

      the only solution is to put an aftermarket damper in the exhaust line, or find a terminal vent that is 100% tight when closed.

  3. calvin | Nov 06, 2009 04:19pm | #4

    If you have easy access and there's a screen on the roof cap that you can easily remove (squeeze lightly and pull out)-

    remove screen, silicone a heavy fender washer on the flapper.  Weight of washer is the key-heavy enough to keep the flapper shut in a wind, light enough that the fan can still push it open.

    Use tape initially to find the proper weight.

    The in the fan flapper is "inside" the pipe opening-never a real good seal.  The roof cap flapper lips over the opening and usually has a minimal gasket.  It seals better if it can stay closed.

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