Am having the same problem with my cabin in North Carolina. When I purchased the cabin I actually had heavy mildew on the wood panel walls and under every cabinet. The cabin sat empty for almost a year with water problems. Previous owner enclosed underpending, but failed to put in vents. To-date I have put automatic vents in the underpending, put down plastic, Washed inside walls with clorox twice and purchased a dehumidifier. My first question is what is a good setting that will not allow mildew to grow? Secondly, I plan to leave the humidifier running after I close and winterize the cabin in Novmber. I have run a hose from the humidifier drain through the floor and out the back underpending wall. How do I keep the water in the hose from freezing and flooding inside?