Holy shit, I’m dense. But so are a lot of other vandwellers. Too many of us 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.
3 Build Strategies Work
1. Side - Reflectix - Furring - Paneling
So how do you correctly use Reflectix in your van for living down by the river? Like they do on roofs and walls! Put furring strips (thin slats of wood, about an inch thick) over the Reflectix, then tack your paneling atop the furring strips. This’ll leave a little air gap between the paneling and the Reflectix.
2. Side - Furring - Reflectix - Paneling
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 fuckin' business.
3. Side - Reflectix - NOTHING
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!
But Use Reflectix on Windows
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 fuckin' V-8!
I've actually given up explaining this to my camper buddies and just sorta smile now. It would appear that you are an exceptional "man", in my experience at least, than most to admit you were doing it wrong. Excellent write up here. Bookmarked to share. ☺️
ReplyDeleteHoping at least one person will learn from my experience, but that's probably too much to hope for.
DeleteI have finally found the HOLY F*** VAN BUILD GRAIL!!!! Thank you! I have been searching for what the hell is a proper air gap and what the hell it is! Simply a damn air gap! Ah hah! I am insulating my van and I do not want to do it wrong, like some you-tubers, it just didn't make sense! BIG QUESTION tho! What if I use a fiber insulation with foil backing, with the foil backing facing inside the van (air space).....but I glue fabric to the foil side? Will the fabric defeat the purpose?
ReplyDeleteIF I now have the correct understandin' ... Yes, it'll decrease the efficiency. The foil will transfer radiant heat to the fibers touchin' the foil, and the fibers will bleed into the air. And the other direction, too.
DeleteMaybe use solid foam insulation, sans foil, and glue the cloth to that. Check this out: https://www.youtube.com/watch?v=HxqPUv2RL_o&t=644s Not sure how it turned out long term, but I bet you can email her.
Hello, I understand: 'Put furring strips (thin slats of wood, about an inch thick) over the Reflectix, then tack your paneling atop the furring strips. This’ll leave a little air gap between the paneling and the Reflectix.' What if FatMat Rattletrap was touching metal and reflectix on top of that and then the wood, is that OK? Thanks.
ReplyDeleteThe FatMat already has an aluminum shield. I'd skip the Reflectix as redundant. I'd stick the FatMat to the sidewall, put in furring strips to create an airgap, then put the wood atop the furring strips. Then the FatMat is also a radiant barrier; it's aluminum shield touching mostly air is the same thing as reflectix.
DeleteThank you.
DeleteWhat about sound deadening foil based butyl like dynamat? Onto the wall of the van? Is this a no no?
ReplyDeleteOh, it's gonna be the same deal. If ya want to use the aluminum foil layer as a radiant barrier, you're gonna have to leave it exposed to air, either showing inside or with a gap between the aluminum and the next wall/insulation layer. The butyl layer will still do it's sound-deafening job whether the foil is touching anything or not.
DeleteI imagine Reflectix became popular (and improperly used) because it's easy to work with. You can cut it with scissors and it bends easily. Foam board, fiberglass batting and such are a pain, especially for people who've never built anything before. So Reflectix sometimes gets seen as the magical solution.
ReplyDeleteThat and it's got buzz.
DeleteSo for slow learners like me..... you need a gap from ceiling and walls. You put wood strips around as a kinda frame. Then to put this foil over it. How do u attach it? What u mean tacks? And the gap. You then attach wood paneling or what ever floats one boat against the foil thing right?. I am from Australia so it's hard to get the products and lingo to sink in. Oh great common sense and building codes in oz. Always say u need a gap between outside cladding and the foil wrap which we use. So I believe u are correct and alot on YouTube are incorrect. Hmmm what a cockup. Wouldn't alot of Van's that be camped for a while have rust on the insides of the van metal frame?
ReplyDelete"to tack" literally means to use a tack, which is like a small nail with a huge, wide, shallow head. They would work to attache the Reflectix to the wood frame. But "to tack" in American lingo also means any way of mounting: nails, spray adhesive, tape, whatever. Not sure what's best for Reflectix and your build. You'll have to research. I ain't no expert.
DeleteThe point of the air gap isn't to breath; it's to prevent heat exchange via conduction. Air is mostly empty space, so heat doesn't move through it a fast as a liquid or solid. So it insulates. That's why a down sleeping bag is so warm: all that air space.
Whether a van rusts inside the wall is just about whether that space -- however tiny -- lets moist air in. As long as ya tape and/or caulk it up good, shouldn't be a problem. No leaks is the key!
This is my first time i visit here. I found so many interesting stuff in your blog especially its discussion. From the tons of comments on your articles, I guess I am not the only one having all the enjoyment here! keep up the good work attic insulation removal and replacement
ReplyDeleteIs an air gap still desirable for windows too or can it be pressed firm against the glass?
ReplyDeleteWell, this is 6 months late but ... no. Ya *could*, I guess, but the main thing is ya got one side a the foil inside the van only touching air.
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