[aerohead]

I'm gonna go with a National Building Code for all recreational vehicles based upon thermodynamics.
The National Home Builders Association members cannot construct a home in the United States unless it meets certain minimum Federal criteria for thermal insulation to control its heating fuel economy/kW-h economy,National Plumbing Codes,National Electrical Codes.
The aerodynamic drag factor of an RV is the same to fuel economy as R-Factor and U-Value is to heating and cooling.
Electric and gas appliances are also subject to Federal standards.
I'm for huge government meddling in the marketplace,with onerous government regulations which mandate the equivalent of draconian CAFE standards for all RVs sold in the USA.
Consumers can remain as ignorant as they like,but they'll be structurally forbidden from purchasing a product which would be the engineering equivalent of a bingo ditch,trash incinerator, or toxic spill; and expect their neighbors to just absorb the insult.
Manufacturers would be totally free to build whatever they like as long as the minimum requirements were met.A level playing field.