Just living in the RV puts an enormous amount of moisture in the air, and that will go right to a cold surface like the frames. Someone mentioned de-humidifiers and if your rig allows for it's size, it's the way to go. Not everyone's does tho, so then open two windows/vents..one each end of the RV to allow for the moisture laden air to flow out. I know..it is counter-intuitive, but it is correct. The moisture will will wick right into soft material like curtains, bedding and clothing. Once you are at that level, you just can't get warm.
Gary Haupt