Help - what do you do with bathroom fans that go....nowhere

[Andrew George Dennis]

I have a two bedroom, two bath condo that I am updating.  It's garden level unit - actually a half way under grade with a crawl space underneath.  The bathroom fans were rattling really bad so I pulled them out and found out the bathroom fans are ventless.  WTF??  They go nowhere (they are just a metal box with charcoal filter and a fan, and there are no windows in the bathrooms.  I found some ventless fans on Amazon that I'm going to put in, but was wondering if anyone has come across this.  If so, did you leave them ventless, and was it a major problem??  This is a condominium, so I can only assume that all the units are like this. I have no roof access, so venting these two bathrooms, which are not on an exterior wall, would be a project for sure.

[Dan Weber]

You don't want to leave it as is because the moisture will be trapped between your ceiling and the floor above you. Can you run hard/flex duct from the fans to the outside of the building and then core a hole in the exterior of the building to vent them?