I am new to TOH, and just starting to try my hand at home projects. One of our baths is damp after a shower, even with a fan running. THere are also water stains on the walls where it is damp (also one spot in the attached bedroom). THere is no bubbling in the paint on the walls. I have two questions: Could this be water coming in from outside, if we have no bubbling? How can we stop dampness? Do we need a new fan, perhaps? Better ventilation? Suggestions?