Installing reflectix on walls and ceilings

[Bluespoet]

I find the installation instructions confusing, in videos I see people just installing it on walls and ceiling, but the installation instruction say dead air spaces both sides.

They really don't address putting relectix in busses. So wonder if I should just put in some foam insulation and then reflectix on top of that, could put in battons or go right against the foam, anyway would love some ideas about how to install on exterior walls and ceilings.

Mine is a airporter style shuttle bus, the walls and ceilings have fiberglass exterior with foam insulation over that and then 1/4" plywood likely melamine for the interior surface. Am going to add insulation to the interior, have the reflectix already, but need to come up with an install plan, any suggestions?

[TAOLIK]

My short summary is you should probably google and study radiant barriers, for reflectix is a radiant barrier. After studying this, you should develop a solution which makes sense to you. However I like talking so I have a long rant for you.

I encountered the same problem specifically regarding reflectix. Some will argue that it's not worth using at all. I do think it is extremely expensive (about the same cost per foot as 1/2" poly iso). But I used the crap out of it and am pretty fond of it. However I can share how I used reflectix, which by no means is correct. In fact it's probably completely incorrect.

I used reflectix primarily as a thermal break/air trap. My logic behind this was "the touch test". Is it cold? okay, lets throw some reflectix on the other side of that. Then smash it in with my insulation panels/fasten with furring strips. I know everyone says 1/8"-3/4" air gap or something along those lines. But for me I justify that the air bubbles in the reflectix are worth some space. Also my work is sloppy enough that I can be confident that there's an airgap with the reflectix no matter how hard I try to get rid of it. I also put long layers of reflectix all over the bus after I insulated the first 1". This was primarily to provide a thermal break between the steel bus with the hopes to eliminate as much thermal bridging as possible. Because the steel studs stick out more than my insulation boards do, I'm confident that there's an airgap there as well.

I made a post which sums this up for the most part, you can find it here.

Ultimately I have developed an ideology towards insulation as a maze for air. Air will get through one way or another, just gotta make it as hard as possible by making lots of twists and curves as well as lounge areas where it can take a rest. Close down the highways (thermal bridging), and make lots of blockades.

Hope this helps a bit.

[Carytowncat]

TAOLIK makes a good point about air. I am amazed at how a simple .5mm plastic over windows works magic. And if i double the plastic layers, its as if there is a supernatural thermal barrier between the cold window and me.

That being said i dream of having the money to pull everything out of the bus and add 3" of rigid insulation lol

It's good to dream

Good luck with the refletix.

[Tango]

I used Reflectix all over my shorty. With the inner panels off, I applied two layers to the outer skin, then another layer to the inner skin. That leaves about 1.25 inch of airspace in between. In a couple of spots I added a layer or two of aluminized 1/2" foam board. Not the R factor you'd get with spray in foam, but that was not an option on my rig.