While we are on the subject, might I also ask a bathroom fan/exhaust question. I don't have a fan in the bathroom of my small old (70s) nothing fancy home. The problem is mildew or mold, whatever that black stuff is the grows on the ceiling. A couple of years ago, a very kind painter painted with KILZ underneath, which stopped it for quite a while.
As other people above, my fear about putting in a fan is that, although this is just a very inexpensive house (basically a tract home), it is very very tight against the very very cold NH winters. And I don't want to interfere with that. I guess a fan could be put in to exhaust either directly out (through the wall), or up into the unfinished attic, or maybe even down into the basement/garage. Any advice or thoughts would be very useful in terms of not having this turn into a fiasco. Thanks! R