Proper installation of Reflectix & foam board?

[Texas Torpedo]

I'm about to head to Lowes to buy a bunch of foam insulation board and Reflectix. I've read a lot of threads both here and elsewhere on the installation of both and I've seen people put the reflectix right up against the outside metal skin, while I've seen others put the foam board against the skin followed by the reflectix and then re-installing the inner paneling board. Could someone in the know explain which was is the proper way?
Also, I've read that to get the best results out of the reflectix installation, there needs to be an air gap between it and the metal skin?

Thanks in advance!
David

[PaulS]

I'm not sure if it was correct but I put it towards the outside on mine because I thought it should reflect the suns heat in the summer time and that is when I would use it the most

[MtnDon]

Any reflective coating on insulation (reflectix bubbles or foil on rigid foam sheets) requires an air space in order to reflect radiant energy. No air space between the foil surface and the next hard surface (inner or outer wall) = no gain in performance. My personal opinion is that reflectix is not worth the money in many cases.

[Rainier70]

I may be wrong, but I would spend the money on another layer of foam board instead.

[asianflava]

I used some kind of paper coated foam board with a reflective side. I put it towards the outside but I've been reading that you want the radiant barrier (in a house attic) on the inside. Honestly, considering the size of a trailer, it probably doesn't make much of a difference. The 5000btu airconditioner in my teardrop will over power any kind of heat I dare camp in.

[abqlloyd]

I would opt for the press on sound deadening material with the reflective back before reflectix, especially on the ceiling. It's more expensive but the space is small. Last year I rode out a small hail storm in an uninsulated CT and it was not fun.

[Texas Torpedo]

Thanks a bunch for all of your feedback. I'm going to go ahead and just get the 3/4" foam board. I have a 12,500 btu a/c unit that should hopefully do the trick and I'm going to coat the roof with a white elastomeric coating as well.