Mold issues in the bathroom are big and is mainly caused by people not running the exhaust fan long enough. One reason for this is that people want to keep the bathroom warm. I recently lucked into a towel falling on the floor which covered the space between the door and the floor. It was significantly warmer when I stepped out of the shower and there was less fog on the mirror.
This led me to the realization that when I would open the window on colder days to see if it would help expel the moist air, this was actually creating more mist as the cool air dropped the temperature of the vapor creating more mist. So in my tiny study it seems best to reduce the introduction of air from outside or other rooms which will keep the vapor high and easily pulled out by the exhaust fan.
Either way, make sure to leave your exhaust fan running for about 15 minutes beyond when your shower ends and help keep your ceilings mold free unlike this one.
Window photo via http://www.flickr.com/photos/iwona_kellie/
