The son is having some work done on his house and wants a bathroom vent fan installed. It is a vaulted ceiling in the midwest, so I'm guessing there is not much room to route a vent pipe unless It goes right out through the roof. I am also guessing, that there is not a vent in there now, but still in code because of a window.
Bath vents, usually around 1250 CFM, will empty a room of conditioned air in short order The make up air has to come from some place and that is outside. So we are pumping heated air out to replaced with cold air in winter and the opposite in the summer. If the vent pipe is not installed correctly, there will be water build up in pipe which will go racid. What's that funny smell?
If there is not a vent installed now, I'm sure the fan will just be wired to come on with the light. Not a problen until one of the kids goes off to school and forgets to turn the light off. Furnace runs all day and now it gets expensive.
What say you? Other than code which was probably introduced in NYC then adopted by everyone else, has anyone thought this through?