I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.