Oh, by the way ... a significant portion of moisture damage on motorhomes actually comes from inside the coach. Humidity from cooking and human and animal respiration migrates through the panelling into the coach framing where it condenses due to colder exterior temperatures.
In the mid-90's, I lived in a place with a ceiling that dripped every spring because of humidity that migrated through the ceiling, condensing and freezing in the insulation above the ceiling, due to no vapor barrier in the ceiling. (The builders assume the foam insulation sheets were enough of a vapor barrier.) When it warmed up enough for the condensation to melt in the spring, the ceiling dripped even though the roof was intact and waterproof.
