EPS has been an excellent choice for an RV wall substrait for years. Normally used as a foam core laminated between an inside and outside skin (usually aluminum) it creates an envelope around the whole RV

A molded roof panel for high volume requirements is a good example of how the initial investment in a tool tool can be offset by the increased savings when compared to cutting and fabricating these same EPS panels. The production cost per unit for molded panels is usually much less than traditionally manufactured roof sheets and/or fabricated parts. Another advantage is the predictable, reliable quality of the molded part when it comes to dimensional tolerances and physical properties.

By also taking a closer look the OEM, E-PAC and Automotive sections on this web-site you'll begin to see how molded foam can be much more than a packaging material.  In fact there are many application in an RV whrere molded foam is replacing wood, metal and hard plastics already (water heater chassis, etc...).