This is a little 23 ft rv, with 2 large dogs and 2 cats. No room for a humidifier anywhere, all I can do is vent it. If not for worry about the animals being cold we'd just leave the heat off more and use another blanket, but I cant leave my animals freeze. I do leave closet doors open and now in the day when windows are open or overnight, take the cushins off the dinette where most to the moisture seems to be. Lousy design as storage under the seats has no doors. Would never even consider plugging up holes or caulking like I would a house, because a house, its not! :)