Re: 1st Floor Bathroom Vent
I would use 3" round, rigid aluminum ducting. Venting to the outside is the only right way to do it. Venting a bath to any enclosed area is a recipe for mold and moisture damage.
Was there no building authority in the area 12 years ago when the house was built? I find it hard to believe that ANY inspector would sign off on the venting prior to sheetrocking, which is required just about everywhere.
If, as you say, all the houses in the area were built that way, you might be able to open a class action suit against the builder(s) and the building authorities. Chances are the members of the class would get $50 each while the lawyers get $5000, but it might be something to look into if it's a BIG problem. (I've never sued anybody or had need for legal advice.)
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.