I had a couple of ADCO covers for my previous class-C. The covers are purposely not waterproof. They only shed water and are meant to breath. If you had a totally waterproof cover, there would be condensation underneath, which would create mold and also would freeze. The biggest problem that I had with the covers is that the wind would cause the cover to rub and create holes at corners like the ladder, topper ends, awning ends, antenna, etc.. I tied foam to these places which helped somewhat, but there was always new places where holes would start. No matter how tight the cover is tied, it is impossible to keep the cover from rippling with the wind.
I therefore gave up with a cover for the Berk. I do suggest that the tires are covered when in standing for any length of time to keep UV off the tires. There are pluses and minuses to covering the RV and is a personal decision.