We were just discussing a similar topic on another forum,,
Homeowner in state "A" says vent into the attic, it will be OK,,
Homeowner in state "B" says NO WAY,, MOLD!
The relative humidity in different states makes both answers possible to be true,,
Vent into an attic in coastal South Carolina, or Florida,, the moisture will destroy the structural wood in the house,,
Vent into an attic in Colorado, the moisture may actually strengthen the house!!
(Just kidding, but, it is dry in CO!)
I would think the
"OTHER" (PHEW!!) reason for bathroom fans would be enough to want to duct the air out of the house!!