It is acceptable to vent a bathroom exhaust fan into a crawlspace?
The crawlspace in question is uninsulated, has a dirt floor, and varies in height between 5' and 7'.
The vent would enter roughly in the middle of about 1000 sq ft or floor area.
The furnace and water heater (both gas) are located fairly close.
Bathroom exhaust vent into crawlspace
bathroomcrawlspaceexhaust-fanvent
Related Solutions
Yikes, this is really the first time I have ever heard of this configuration. Could this have been part of a previous central forced hot air system? It is not common to tie exhaust vents from a bathroom to any other living space. A dedicated exhaust fan vented to outdoors with a one way damper is a very important way to remove excess moisture from bathrooms and help prevent mold and mildew growth. It is not acceptable to vent a bathroom to another living space or into an attic. It is equally not right to tie this type of vent to any other air plenum. If you are feeling cold outside air through these vents, you are getting huge heat losses. There is no need to introduce outdoor air into your house intentionally unless it is done with specifically designed air exchange equipment in an extremely airtight designed house. I think you need to determine the routing of these "phantom" vents and come up with a plan to isolate the bath vents to the out of doors with a proper bathroom fan unit and block your heat form other areas from being wasted out an open plenum.
I used something like this (4 in. Round Wall Vent). It only flaps when the wind is really blowing.
Here is another option that should have no clickey clackey at all:
Cape style backdraft damper
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Best Answer
No, at least not under the international residential code (IRC):
And more specifically:
The reasoning is simple: the exhausted air is likely to contain a lot of moisture, and will therefore result in mold growth in your crawlspace. Your local codes may differ depending on where you live, but it's still not a good idea.