I am in the middle of insulating the floor of my RW 30 C. I first installed 25' of foam pipe insulation on all of the water lines including those that were between the black plastic lining and the fiberglass insulation. Had to re-route the main water line from the two tanks as they were routed between the coroplast and the cross frame members. After insulating the water lines I then glued 1.5 " white foam board to the interior of the main frame members and used expanding foam to plug the numerous penetrations for the wiring bundles, water hoses, gas lines and just holes in the main frame. at the fron I have the black tank and gray tank so used 1" white foam board wedged over the frame lip on the sides and taped the perimeter of the foam where it meets the steel frame. Under the two water tanks I am using 1/2" pink foam board. in other areas where there is sufficient clearance, I. Use 1.5 white foam board. the garage area in the toy haulers is not insulated so I used 2" pink foam placed between the frame members and screwed into the 1" plywood floor. Then I covered the 2" foam with a 1" white foam board with the reflecting/shiny side out to reflect away the road heat. I can't believe that the factory thinks that blowing heat into an I insulated area with numerous penetrations is going to keep anything from freezing. I've got 3 part days into this project and I'm only half done. I've used 3 sheets of 1" foam board, 2 sheets of 1/2", 4 sheets of 1.5" and 2 sheets of 2", couple tubes of foam board floe, 2 cans of spray foam and 1 roll of gorilla tape.