Cooling Issues in my stealth camper

I found a material with foil on one side and it is very light but doesn't appear to be very flammable. Forgot what it's called but home depot carries it. It has both a radiant barrier and it has a decent R value as well, I think it's about 3/4 of an inch thick. I'm going to line the inside of the trailer with this stuff and I should be adequately insulated. It will certainly be a vast improvement on what's there now. If I can take off the paneling and replace the insulation there, and put the paneling back on and it tests out great, I'll just stop there.

Reflectix,a radiant barrier attached to bubble wrap. It would certainly help with insulation but I'd suggest you use foam board cut/fit into the cavities. The bubble wrap material only has the R-value of the depth of the material (around R-1?). 1/2" barrier-faced extruded polyethylene foam board will be around R-5 or so.

If you want it even better insulated, staple a 1/4" foam panel over the frame and the insulated cavities. That will give you a thermal break, When I did mine, I also installed a full 4 mil vapor barrier for condensation and air migration. 4 mil also rates R-1,