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Insulating using ONLY Reflectix in cavities, the right way!
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Insulate van cavities using only Reflectix?
Simple setup: 2 layers on glued on each side, metal + panel
40%
 40%  [ 4 ]
Complex setup: 3 layers, simple setup + additional layer in between
0%
 0%  [ 0 ]
Don’t insulate using just Reflectix
60%
 60%  [ 6 ]
Total Votes : 10

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T3TRIS
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PostPosted: Mon Sep 17, 2018 5:39 pm    Post subject: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

In the never ending subject of insulation, there’s a scenario I haven’t seen implemented (and please correct me if I’m wrong or missed it in my searches). That is insulating your van using only Reflectix, the right way!
Now, I’m not talking about just (wrongfully) putting one layer on the metal of the van and using Reflectix on a window. What I had in mind was more like creating a Reflectix air cavity inside the walls and doors. Reflectix only works well as an insulator if it has at least 3/4” of air on one side, or both. Using only Reflectix would simplify installation and save weight.

Has anyone tried or tested any of the following two scenarios:
- Simple setup: one layer of Reflectix glued to the metal side of the cavity and another layer glued to the interior panel, creating an air cavity around 2-1/2” with Reflectix on both sides?
- More complex setup: same method as above but adding yet another layer in-between using furring strips to maintain two air cavities of a little over 1” each? (Relfectix Big Mac anyone?)

Any thought? First hand experience? Pros and cons? Issues with condensation? Not worth the insulation value?
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flomulgator
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PostPosted: Tue Sep 18, 2018 9:56 am    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

I did an even simpler version:
butyl rubber Fatmat stuck to the body panels (for sound insulation, but also reduces the thermal conductivity of the sheet metal) then one layer of Reflectix cut to size and floating around in each panel. Each piece is somewhat held in place by being cut to the panel size which is larger than the bracing it must pass through. In theory, it will have some air on each side, but even if it is just laying against the trim panel or Fatmat the Reflectix is a closed cell system so it does not need an air gap to insulate. Like any insulator it will work better with more trapped "cells" of air behind it, or more layers, but it functionally insulates the same way as any camping sleeping pad on it's own.

The primary benefits of this installation are ease of installation, less material cost, and lower moisture retention. It provided a noticeable benefit in winter heat retention.
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bobbyblack Premium Member
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PostPosted: Tue Sep 18, 2018 11:28 am    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

I've got no vote, but several conflicting notions.

#1; on my summer trip with the kids, elevation changes from 1100 ft at home to over 9000 ft in 'mountains' resulted in two interesting results; Bag of chips which were purchased at home and not yet opened by the top height of our climb was a bloated balloon like object. Keep this in mind with 'cells' you put into places that would suffer from bloating.

#2; from memory, behind each panel down at the bottom, there are usually manufacturer's "weep holes" for the inevitable infiltration of some moisture, so it can escape. Means you won't get an actual seal of any sort in the cavity.

As most folks know, the use of air pockets between cold/warm/hot is mostly what keeps heat from traveling, and the silvery part is useful mostly to show off that you've got it insulated. So, the lots of little bubbles of air in the silver stuff is what does most of the work. Not saying the silver part does nothing, but it is way less than the air pockets. That being said, the thickness of the material is inherently what you'll want to be concerned with, rather than the silver coating.

I think its at least worth a conceptual visit.
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danfromsyr
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PostPosted: Tue Sep 18, 2018 11:46 am    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

heres a dont use reflectix vote
https://vacayvans.com/camper-van-insulation-reflectix-wool-spray-foam/
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T3TRIS
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PostPosted: Wed Sep 19, 2018 4:21 pm    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

danfromsyr wrote:
heres a dont use reflectix vote
https://vacayvans.com/camper-van-insulation-reflectix-wool-spray-foam/


Yeah. That’s why I tried to insist on doing it the “right way” by making sure there is the required air gap and nothing else.
Per that website: “The problem is that everyone we’ve seen is installing Reflectix incorrectly, which renders the product useless.”
According to the video they show, the radiant foil is only letting about 3% of the heat go through with the air gap.
Again per the website: “For installation to be correct, there MUST be an air gap of at least 3/4″ between the foil and any other material. If there is no air gap, the foil acts as a conductor and will actually work against you!”
And: “To properly install a radiant barrier in your van just isn’t feasible– you would need to run ¾” furr strips around the entire interior of your van and then ensure no insulation or paneling touches the foil. This would take up a LOT of valuable space in your van.”

As I mentioned, I’m talking about installing it correctly AND using the van’s existing cavities as air gaps, not filling them with insulation. This is not a poll on comparing poorly installed Reflectix VS foam. It’s not about how Reflectix is poor with conduction. Whomever responded to the poll without understanding that is skewing the results by not grasping the concept, rendering the results useless.

I agree with all the conclusions that putting a layer of Reflectix inside your van straight on the metal then slapping a piece of foam insulation right onto it is useless. I agree that adding at least 3/4 inch of air gap inside the van is inconvenient. I agree that most people install it wrong.

Reflectix is really good at reflecting heat when there’s an air gap, so. If we put a layer inside the walls, onto the metal and a layer onto the back side of our panels with no insulation, that creates a 2-1/2” air gap (not super sealed as bobbyblack pointed out). Radiant heat from outside would pass through the first layer (on the metal), through the 2-1/2 air gap and hit the correctly installed second layer of Reflectix (on the panel) and would be reflected. The same applies to radiant heat trying to escape the van when it’s cold out. It’d make it through the panel, then the air gap and would now be reflected by the Reflectix on the metal. One question is: am I just trapping radiant heat inside the walls of the van?

That’s one reason why I suggested the other scenario, with the additional layer of Reflectix floating inside the wall, in the middle, with two sufficient air gaps on each side. Hopefully that’d just make the RADIANT insulation value much better.

Does any of this make sense? People love to bash on Reflectix and with good reasons when it’s improperly installed. But that’s always what it seems to be left at, just imporperly installed. Does it work well when properly installed?
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DanHoug
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PostPosted: Wed Sep 19, 2018 4:38 pm    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

ANY foil faced insulating panel requires the air gap. it's a matter of infrared physics. there's very detailed info on foil faced foam insulating panels of the R value vs air gap. search Celotex for example. the Reflectix has some R value in and of itself, which can be useful but must have the air gap to achieve its magic properties. otherwise, just use closed cell foam which can be less expensive.
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nemobuscaptain
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PostPosted: Thu Sep 20, 2018 5:12 pm    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

All insulation involves trapped air. Period. Reflecting radiant heat is not insulation. I like reflectix on my windows, just fine.

The problem with trapped air is you end up with a cold metal (colder than if you had some heat source inside two bodies, whatever, and no insulation anyway) and lots of humidty on the inside. Condensation will occur. Rust is shortly behind. Vapor barrier never works because you simply can't seal it all. Even the seam likely isn't completely sealed.

I live in the humidity zone, and I'm way more concerned about keep the inside of my panels dry and rust free than insulated.

Not sure why every one is in a hurry to insulate. That stuff inevitably causes rust and frankly, with may windows and a perhaps a poorly sealed poptop, never causes the slightest difference in temp anyway.

I'd really like to see some tests of temperatures of two similar busses with and without insulation.

While you are at it, take the bullshit insulation Westy put in the driver's side wall and fix the rust it caused. Busses that came from the factory without that crap insulation never seem to have that seam rust.
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westyventures
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PostPosted: Fri Sep 21, 2018 10:43 am    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

/\ /\ /\ Ha!

Might as well not insulate homes either!

Data point: my previous Syncro Westy: QuietCoat sound deadener sprayed in all the interior walls, followed with Enguard insulation. Incredible difference in HOT and COLD weather, not to mention the huge reduction in noise inside when camping or driving. In one instance when I owned it, in -10 weather a few nights, the Espar diesel furnace was only running at stage 2 (of 4) at night to maintain 70 degrees inside. It just returned from 21 months on the road through Latin America (with 'new' owners), through some horribly humid weather and other weather extremes, no issues whatsoever with rust or water soak.
But as previously mentioned, the only place silver bubble wrap is of any good is for windows. If you're going to insulate walls, use a real [non-fiberglass] insulation. Unless your van is riddled with rust or bare metal with zero paint inside, it won't cause rust to happen.
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T3TRIS
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PostPosted: Sun Sep 23, 2018 10:27 pm    Post subject: Re: Insulating using ONLY Reflectix in cavities, the right way! Reply with quote

nemobuscaptain wrote:
All insulation involves trapped air. Period. Reflecting radiant heat is not insulation. I like reflectix on my windows, just fine.

The problem with trapped air is you end up with a cold metal (colder than if you had some heat source inside two bodies, whatever, and no insulation anyway) and lots of humidty on the inside. Condensation will occur. Rust is shortly behind. Vapor barrier never works because you simply can't seal it all. Even the seam likely isn't completely sealed.

I live in the humidity zone, and I'm way more concerned about keep the inside of my panels dry and rust free than insulated.

Not sure why every one is in a hurry to insulate. That stuff inevitably causes rust and frankly, with may windows and a perhaps a poorly sealed poptop, never causes the slightest difference in temp anyway.

I'd really like to see some tests of temperatures of two similar busses with and without insulation.

While you are at it, take the bullshit insulation Westy put in the driver's side wall and fix the rust it caused. Busses that came from the factory without that crap insulation never seem to have that seam rust.


I had heard about the train of thought that insulation is supposedly useless if you have an area that has significantly worse insulation, or thermal bridging. I don't necessarily think it's the case and believe some insulation is better than no insulation (as long as it doesn't create condensation/rust). If you can insulate parts of a van without creating additional rust, it can't hurt! Sure we can debate the usefulness of a small insulated section vs big windows, but if we can insulate our floors, most of the metal on the side panels and a little bit of roof, it has to make a measurable difference compared to an uninsulated van. Just as westyventures mentioned.

Thanks for the rust comment, I wasn't thinking about creating condensation with a method like this one.
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