"(from Ask Ed) Our windows have a lot of moisture inside due to humidity. We run a dehumidifier, what else can we do?...."
Link: Ed Del Grande: Ask Ed -- Wet Windows (HGTVPro.com)
[I have this problem too. On really cold mornings, we have to wipe the windows down at least twice. Only one bathroom has a fan. (The others have windows.) I wonder if that would work.]