R values are pretty meaningless. First, there is only so much insulation that can be installed in a 2" thick wall and almost every manufacturer plays the trick of claiming the "best case calculated R value". Yet substantial areas of the RV are much worse. That combined with substantial air leaks in all trailers has a much bigger impact on interior comfort than the "best case" numbers.
Examples: 1) 25% of the floor area has much less insulation, the area between the frame rails and outside walls is just the thickness of the floor joist (about 3 inches) vs. the underbelly area between the frame rails. 2) the interior wall of the frig. cabinet have almost zero insulation even though the backside is exposed to the full range of outside temps in summer and winter. 3) slideout walls, roof and floor are thinner and have less insulation than the main body, surface area will be substantial with multiple slideouts. 4) everyone uses Reflectix foil insulation and claims the "equivalent" R value even when installed wrong and in places that are almost devoid of IR rays to reflect.
I could go on, but there are just so many weaknesses, too many to fully list.
Texas Baptist Men-Retiree Builders member since '01
13 Silverado 3500HD D/A, 2wd CCSB srw, custom RKI bed
11 Cruiser CF32MK