[Exeric]

Michael, one more thing to think about. It sounded like you weren't using forced air for the temperature conditioning system of your house. Perhaps I'm wrong. But if you aren't that means if you have the bedroom doors closed at night for a guest or to conserve temperature in the bedrooms, then air in the bedrooms will no longer circulate from a bathroom fan. It doesn't sound like you'll have the temperature problem but you will have the air circulation problem if the bedroom doors are closed at night.

The house I'm renovating doesn't have forced air either and will just use a bathroom fan. To get around the stagnant bedroom air at night I'm going to put a return air duct from the bathroom floor to the bedroom floor through floor registers. I also plan on putting another return air duct high up on the walls in each bedroom that separates the bedrooms from the living room. That way I'm creating a path for warm air near the ceiling in the living room to move into the bedrooms at night. The colder air near the floor in the bedrooms will be sucked into the bathroom from the bathroom fan through the floor registers connecting the bathroom and bedrooms.

The plan is to not undercut the bathroom door as is usually done on the bathroom door to provide air circulation. Instead I'll just keep the bathroom door closed at night and then force the air circulation path through the bedrooms. Hopefully it will also let me turn down the heat at night and use the main living space for the heat reservoir helping to heat the bedrooms at night (or during the day). I hope it works.