Holy shit, I’m dense. But so are a lot of other vandwellers. Too many of use Reflectix wrong. I did. Big waste of time and money. Know why?
No Air Gap = No Good
What Vanholio did was put closed foam insulation against the metal wall, Reflectix against that, and then plywood paneling against the Reflectix. All touching. Stupid, stupid, stupid!
At least my Reflectix is tape-sealed to the wall. It’s an expensive vapor barrier now. I coulda used cheaper foil or plastic, though.
(Well, supposedly the bubble wrap part has an R-value of 1.1. But I’m skeptical.)
And no, pressing your Reflectix up against fluffy, "airy" fiberglass batting like this guy did doesn’t count. It needs to be air, plain old air. If that foil touches *anything*, it stops being a reflector/non-emitter and becomes a conductor. The heat energy will just pass on through to whatever it’s touching. (See the video at bottom.)
OK, you can read about “The Physics of Foil” if you want to get your egghead on. Bottom line though: No Air Gap = No Good. The Reflectix company themselves says that on their website.
You could also do it the other way round: put the furring strips on the metal, and the Reflectix over that, then paneling. So long as you get your air gap, you're in fucking business.
Another option: Dispense with the furring strips and leave the Reflectix exposed. The van interior becomes the air gap then.
But maybe it’s not even worth it then. Especially if you’re tight on space. You might be better off using straight foam insulation (or wool, or fiberglass batting, or cellulose, or etc.).
Or if you live in a hot, sunny place and just want to reflect solar radiation, cheaper foil insulation would be just as good. Hell, you could glue up Reynold’s Wrap! Just leave it exposed to your interior. Might be ugly, but it'll work!
The one place Reflectix rocks is windows. Yes, you could use plain old foil, like every trashy house and trailer in America. But the bubble wrap interior gives Reflectix some structure to bear taking up and down. I assume you don’t want foil in your windows all the goddamned time!
Still don’t get why Reflectix in your van walls *must* have an air gap? Don’t believe all those van conversions you saw online are wrong? Watch this video below. You’ll wish you coulda had a fucking V-8!