Carpet Concept - Reflectix is Worthless

[Ballenxj]

As for the van with solar, a 1" gap beneath the panels would shadow the roof and make it much cooler.  
The 1" gap would be a handy place to store pull-out shades for the side windows.

My unproven theory is that while the panels give shade and help cool the section of roof they cover, the one inch or more space underneath would act like an attic vent in an abstract sort of way. Hey, it sounded good to me?  
Anyway, that, in conjunction with window covering, decent insulation and proper ventilation in my opinion would go a long ways to help keeping the van cooler in summer months.