For you poor soles that don't have covered parking I am trying out an rv cover. Kind of spendy but I found one on sale. Hopefully it will last a few seasons, supposed to be mildew resistant, and breathable. Check out the pics. I can roll up the sides and access the rig from all doors!
http://m.campingworld.com/shopping/item/classic-accessories-polypro-3-class-b-rv-cover-fits-20-23/60299