Using Reflectix / Rattletrap Incorrectly? - I am rethinking my insulation approach...

Midwestdrifter

Engineer In Residence
When you say 'judiciously', do you have any pointers on what would that be? As a dampener, would it work better cut into strips with open metal in between? Or around the edge of the space, or completely covering 'noisy' places like the wheel wells?
Ideal coverage is 25% of large non braced panels. Stiff or curved panels will receive little or no benefit from the CLD materials.
 

hein

Van Guru
When you say 'judiciously', do you have any pointers on what would that be? As a dampener, would it work better cut into strips with open metal in between? Or around the edge of the space, or completely covering 'noisy' places like the wheel wells?
Thinsulate(TM) is great at killing resonance in panels. In addition to providing R-value and noise absorption. This mostly eliminates the need to mass loaded or mass loading products like Dynamat, Fatmat, etc.
 

mountainhick

Active member

randomgood

New member
So is foil insulation completely out now.
I had considered cutting it into strips and placing it in the groves under the factory wood floor and a thin layer of foam.
Is this just a waist of time, or will it still provide some benefit.

We camp exclusively in the spring, summer and fall.
 

Midwestdrifter

Engineer In Residence
So is foil insulation completely out now.
I had considered cutting it into strips and placing it in the groves under the factory wood floor and a thin layer of foam.
Is this just a waist of time, or will it still provide some benefit.

We camp exclusively in the spring, summer and fall.
I did something similar. I filled the floor corrugations with a single layer of reflectix, and then used 1/2" of rigid foam, followed by the factory floor. The result was good enough for our usage.

The reflectix was cheap, and an easy way to add a small additional R value as there was a 1/4" tall air space between the corrugations.
 
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JFloFoto

Active member
Does anyone have experience with this product - UltraTouch insulation? It is a foil faced insulation with recycled natural-fiber padding. Available through Home Depot and cheap.

UltraTouch link

 
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PaulDavis

Member
Does anyone have experience with this product - UltraTouch insulation? It is a foil faced insulation with recycled natural-fiber padding. Available through Home Depot and cheap.
the fiber isn't hydrophobic, so it will trap moisture. in many places, that can lead to mold and rust issues.
 

DieselFumes

2015 4x4 2500 170 Crew
I'm liking the idea of Thermozite Thermal Acoustic Insulation glued in alum side towards steel to reflect heat out and a another later of Jute insulation pad glued on top.

See RB Components / insulation @: http://www.rbcomponents.com/sprinter-van/sprinter-van-interior/insulation

I think I'll use "Rattletrap" only on the inside of the doors, including the front if I can get in there.
If you glue an aluminum foil faced product to the steel wall of your van, it will not reflect heat out. It will conduct heat. The foil faced products will only reflect heat when they have an air gap between them and the heat source. That's probably why RB says "The tough aluminum foil side provides a radiant heat shield which can increase themal resistance ® up to a factor of four (depending on distance from heat source)"

The jute layer is also a potential concern. Jute is a natural fiber and it may want to absorb moisture. That would be bad in a conversion van because it can encourage rust.

You can read more about radiant barrier products (foil faced foam) here.
 

DieselFumes

2015 4x4 2500 170 Crew
where will it conduct it to? will it be somewhere that the heat wasn't going to reach without the reflectix?
Nope, but it won't have any insulating effect either. Lots of people appear to read the R numbers for foil faced products and believe that they apply in every situation. They don't. The R numbers claimed by the foil faced product manufacturers assume air gaps. Even then the numbers are dubious. If you were to use Reflectix next to the metal, you might just as well use the plastic bubble stuff. Same with this jute one - might just as well use the jute without the foil.

My point being, the foil faced products insulate by reflection, not (lack of) conduction. If you use them incorrectly, they aren't going to be as useful as some other type of insulation you could have used instead. Just trying to safe people time, money, and aggravation.

We used LowE in those floor indentations because I had some left over, but we did it for the (marginal) noise reduction that the foam provides, not for any magical R value that it surely does not provide in that location.
 

PaulDavis

Member
Nope, but it won't have any insulating effect either.
That's my point. It is accurate to say that the reflection-based "insulative" property is lost in this configuration. It isn't accurate to say that it will "conduct" because that requires a heat conducting pathway from the van body to the foil face on the inside of the van. This will rarely exist (though it may).

If you were to use Reflectix next to the metal, you might just as well use the plastic bubble stuff.
Agreed. The foil does provide a little bit of stiffening though, perhaps, and an easy surface to apply glue or whatever.

My point being, the foil faced products insulate by reflection, not (lack of) conduction.
I think the immobilised air gap(s) provide a very small amount of insulation. Not much, for sure.

We used LowE in those floor indentations because I had some left over, but we did it for the (marginal) noise reduction that the foam provides, not for any magical R value that it surely does not provide in that location.
closed cell foam in the floor: best of both worlds.
 

DieselFumes

2015 4x4 2500 170 Crew
That's my point. It is accurate to say that the reflection-based "insulative" property is lost in this configuration. It isn't accurate to say that it will "conduct" because that requires a heat conducting pathway from the van body to the foil face on the inside of the van. This will rarely exist (though it may).
I think we're agreeing. The aluminum will conduct heat from the van wall. It won't necessarily conduct it to anywhere else, but it'll conduct to/through/along the foil itself. i.e. the foil is conductive. Hair splitting, probably.
 

continuous

New member
I know the thread is quite old, but here is my contribution - as an engineer and physicist and not as a layman or a salesman.

There are only two things to know and apply to your specific situation in relation to heat:

1/ only surfaces radiate heat, the greater the temperature difference of the surface to the space in question the more it will radiate, and

2/ all things resist the flow of heat - some more than others - metal extremely poorly, plastic so - so, air good and vacuum perfectly.

The van body heats up in the sun because it absorbs heat from the sun - how much it absorbs depends on how long it is exposed and its infrared "colour" foil for example is a good reflector, matt black is not. Given enough time however the body will heat up to the same temperature regardless of the colour. (almost the same...too much detail and too small an issue to go into it)

As the sheet metal of the van body gets hotter it radiates heat more and in all directions - out and in - equally. The hotter it gets the more it radiates.

By putting in an insulator (foam or aerogel or anything that resists the flow of heat substantially) inside the van you slow the transfer of that heat to the inside surface of the insulator.

The cooler the surface of the insulator inside the van, the less it will radiate heat and therefore the interior will remain cooler for longer. The thicker the insulation layer the longer it will take to heat the inside surface of the insulator so the van will stay cooler longer.

Foil on the inside will do nothing to reduce this heating of the foam inside surface - but it will keep the heat in by reflecting it back into the vehicle - that is good when it is cold outside.

Ofcourse in hot weather any insulation can be avoided by putting a tarp or fly with an air gap over the van to stop the sun heating the metal in the first place.

Then there is the question of heat coming in through by convection - that is just the flow of hot air. Just keep the doors closed and any vents and make sure they seal properly. If you plan to live inside, then you can't avoid heating by convection - you need air.
 
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Nomad_Elvis

Guest
...Given enough time however the body will heat up to the same temperature regardless of the colour. (almost the same...
I'd have to take exception to that. What you say is true if the body is in a vacuum, but not if surrounded by an atmosphere, because different characteristics (surface finish, etc.) affect the rate at which heat is dissipated to the atmosphere, a variable that doesn't exist in a vacuum.

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For those interested in more info about using reflectix & other materials for insulating a van, here's some more info...

Here's why gluing a single layer of Reflectix to the interior surface of the metal skin of the vehicle is actually not a bad idea, but there are better alternatives.
First, a quick look at the physics involved:

The thermal energy in sunlight is approximately 52% in the narrow infrared & near-infrared part of the spectrum, and 48% in every other part (visible light). When sunlight hits a surface, the visible light that is not reflected is converted to heat energy, and some of that heat is absorbed and some is rejected, depending on the color and other factors. As the energy from the sunlight is absorbed by the sheet metal skin of a van, all of the energy that is not reflected or dissipated to the atmosphere is transmitted to the interior in the form of heat energy.

That incoming heat energy from sunlight can be conveyed to the interior of the van by one of three methods (conduction, convection or radiation) as has already been discussed. "Radiation" is just another term for infrared energy, more of which is emitted by an object as its temperature rises (all else being equal).

Radiant barriers work because they have low "emissivity" ("Low-E") which means they do not readily emit infrared energy. Reflectix and other metallic barriers (anf even household aluminum foil) typically emit less than 5% of the heat energy as infrared radiation. In comparison, most plastics and most paints emit over 80%, and a van upfit can be designed to take advantage of that.

In stock form, the inside of a van's exterior skin has infrared emissivity that is almost as high as the paint on the outside.
That means that in stock form, almost as much radiant heat energy is emitted inwardly as outwardly.

But if a radiant barrier is applied to the inside of a van's exterior skin, the interior of that barrier will emit (radiate) heat inwardly at a much lower rate than the exterior surface. This will cause relatively more heat to be rejected outwardly (where it will be dissipated to the air) rather than inwardly (relative to the temperature differential), which is desirable in this application (at least on a hot summer day).

However, it does not have to be Reflectix or a similar metalized bubble wrap product.

A foil layer will work almost as well, *AS LONG AS A SEALED AIR GAP IS MAINTAINED ON THE INSIDE OF THAT MATERIAL,* and assuming that bulk thermal insulation (the kind that has "real" R-value, like rigid foam) is installed on the inner side of that air gap. And two foil layers with an air gap between them will work slightly better than a single layer of "double-bubble" Reflectix.

Here are the layers for optimal insulation, from outside to inside:

1. OEM Sheet Metal skin
2. Radiant Barrier Foil, glued to skin
3. AIR GAP, 1/4" minimum (preferably 1/2"-3/4") with all gaps, top, bottom, sides, etc. closed off.
4. Radiant Barrier Foil...
5. ...on bulk ("real" R-Value rating) foam insulation (Polyiso if primary concern is summer heat. JohnsManville AP Foil is acceptable, but it's not quite as good as Dow Tuff-R or Dow Thermax.)
Avoid using the "Rmax R-Matte" product sold at Home Depot if possible, because it is inferior to Tuff-R or AP Foil.

Of course, don't forget about the glass area. Everybody knows that, but what they may not know is that exterior sunshades are about twice as effective at keeping heat out as anything installed inside the glass. Reflectix works OK for that but there are a few better products available (but not at local Lowes or HD).

Beyond that, the only other way to do any better for reducing heat gain on a sunny summer day is to paint the exterior with a high performance roof coating, with a "Solar Reflective Index" of 110 or better, such as Gardner S-100.

The only advantage Reflectix has over single layer of foil (like Attic foil) in this application is that Reflectix is technically a double layer radiant barrier separated by a pseudo-air-gap. But unfortunately there is a lot of plastic bridging those two surfaces, so Reflectix is actually not as effective as two layers of foil separated by a true air gap. Sometimes it's hard to maintain a true sealed air gap everywhere in a vehicle installation, and that's why one layer of Reflectix is not a terrible choice, especially since it doesn't take a huge quantity just to do a van, and local Lowes/Home Depot carry it (but generally do not stock radiant barrier foil like Attic Foil, etc.).

The bottom line is: Reflectix will reduce heat transfer to the interior of a van if applied directly to the inside of a van's exterior skin, but any radiant barrier product needs to be part of a more extensive insulation system using conventional bulk thermal insulation, and frankly, there are better options than Reflectix for this application.

There are generic equivalents of Reflectix available online, but here is what I recommend using instead of any "bubble-foil" product, for the inside of a van's skin:
1. Single layer non-perforated (solid) foil, e.g. www.atticfoil.com/index.php/products/
2. Silent Silver Underlayment (or equivalent), radiant barrier + acoustic dampening https://www.rubberflooringinc.com/underlayment/silent-silver-underlayment.html

Either one of these can be applied directly to the inside of the sheet metal but needs 1/4" air gap at the very minimum between it and additional insulation, and preferably at least 1/2" (more than 3/4" adds nothing, according to specs from Dow, and JohnsManville). The bulk insulation added on the inside of that air gap should also have a foil (both Tuff-R & AP Foil do) facing the air gap.

As for the spray-applied expanding foams (e.g.: "Great Stuff): These one-component spray foams sold at Lowes & Home Depot do not have nearly as high closed cell percentage as two-part foams, and that's the main reason they can trap water, either from leaks or condensation. The R-value of these foams is not as high as 2-part foams.

Manufactured polyiso foam sheathing is always preferable to field-sprayed foams because the manufactured foam is the only type that actually achieves its rated R-value; even professional spray application is not as consistent as the manufactured boards. The generally accepted "real-world" R-value for field-sprayed polyiso foam is R 5.6 per inch, but only in mild temps, because the R-Value of all Polyiso foam (sheet & sprayed) drops substantially in very cold temperatures.

For filling voids, two part foams are greatly preferable, and cheaper than 2-part spray foam: http://www.uscomposites.com/foam.html
and they do not corrode sheet metal or trap water unless water was present when they are poured.
In some cases, non-rigid foam is needed: https://www.smooth-on.com/product-line/flexfoam-it/

Two-part foams must be mixed correctly and applied at room temperature to expand fully. There are also DIY two-part spray foam units available, but they aren't cheap.
It is preferable to use foam sheathing in any area where that is possible, because it is a more consistent product that will maintain its R-Value longer than any field-applied foam.

I hope this helps.

I posted this here after getting frustrated by all the misinformation that seems to be so prevalent on youtube.
Seems like everybody's got a video up of their van-to-RV upfit, and based on the comments I saw, a lot of people getting misled too.

FWIW, I design RVs for a local upfitter, and am up to date with the latest ways to squeeze out every last wasted BTU or watt-hour.
Here are two of my favorite go-too components:
http://www.hotspotenergy.com/DC-air-conditioner/
http://www.lensunsolar.com/Flexible-solar-panel/Aluminum-flexible-solar-panel

Important note: if you glue PV panels down to the exterior skin of an RV, you loose one of the other advantages that an aluminum-backed PV panel can provide:
shade... which you will have if there's an air gap under it. :thumbup:

...
 
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roblee

Member
Interesting that last 2 posters were first time posters. Both sound learned and each has helpful info but very different conclusions. Continuous says not a salesman, Elvis is an upfitter. Big difference is what they think of reflectix in a van. My take is reflectix is not magical. It is about 1/4" thick with a R of about 1; despite sales spin. The air gap systems described in DOE research are complex, 18+" thick, and have a continuous air exchange in the air gap. This just isn't possible in a van. Air gap from shade? That works wonders.
 

hein

Van Guru
Thank you for joining the discussion and sharing your knowledge and insights.

Please be aware that materials used in vehicles should pass FMVSS-302.
Thinsulate(TM) and Low-E SSR(TM) meet this requirement.

Insulating a van does not need to be a science project. Our system, methods and
materials provide a great balance between ease of installation and performance.
 
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Nomad_Elvis

Guest
Thank you for joining the discussion and sharing your knowledge and insights.

Please be aware that materials used in vehicles should pass FMVSS-302.
Thinsulate(TM) and Low-E SSR(TM) meet this requirement.

Insulating a van does not need to be a science project. Our system, methods and
materials provide a great balance between ease of installation and performance.
I only posted here in this forum because one of my searches for something unrelated happened to direct me to this thread, where I saw evidence that a people had a lot of about uncertainties about best materials for this application.

For anyone who has concerns about FMVSS-302 (which is not a particularly stringent standard) I'd suggest researching the relationship between the testing used for a Class A fire rating and FMVSS-302. That way you won't have to take it from what you saw posted on the internet by some guy named 'Elvis.'

FWIW, the "Low-E SSR(TM)" is not a special or improved variation of ESP's "Low-E."
It is just "Simple Solution Rolls," meaning small rolls sold for small DIY projects.

I am very familiar with both ESP's Low-E and 3M Thinsulate.
Neither one has been used in any of the builds I've designed since the first cost-benefit analysis I conducted back in 2006.


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ESP Low-E is one of the very thin foil-faced foam/bubble/fiber products that Ed mentions in this video:
https://www.youtube.com/watch?v=Vl8GslJ9hnI
For anyone who wants to cut to the chase, the bottom line starts at 4:45

Please note: I am not Ed, nor do I have any affiliation of any kind with Ed.
I sometimes cite his videos because they are (mostly) accurate, unlike a lot of the other information out there.

Like Reflectix, Low-E has a true R-value (which is a measure of conductive heat flow resistance) of no more than the foam substrate (polyethylene in this case).
Polyethylene foam one of the poorest performers of commonly available foams, with an R-value barely R3 per inch.
Practically every other foam: carpet foam, styrofoam, polyester foam, etc, are at least 30% better than polyethylene as an insulator.

Polyethylene does have one key advantage though: it's cheap.
LDPE is the least expensive of the commonly available plastics, and that's why it's used for so many consumer products.

We tested ESP Low-E twice over the years, and it proved to be a low performer at a relatively high cost (compared to comparable products), making it a poor value compared to some of the alternatives.

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3M Thinsulate is mainly intended for acoustic insulation:


...and it does a pretty good job at that too, but only the thickest versions have decent performance at the lower frequencies that are the most problematical in RVs:


Thinsulate has a fairly good resistance to heat flow (like most acoustic absorbers, about half that of polyiso foam).
Thinsulate variants with better acoustic performance (e.g.: SM 600L) have worse thermal performance (R3.15 per inch):


Thinsulate is as easy to install as flexible foam, but that comes with a tradeoff: its performance depends on a carefully designed fiber structure, which means that areas compressed during installation lose some of their acoustic & thermal performance.

Thinsulate is a pretty good product for OEMs: it is designed to be easily integrated into mass production, and large OEMs can buy it at a fraction of the cost of what it normally costs DIYers.

Thinsulate is also good for DIYers who are willing to get ease of installation in exchange for high cost and fairly good performance.
In that case (ease of installation & fairly good performance), there are other options, commonly available in most large cities, that mostly provide those attributes at lower cost.
My first post provides guidance for anyone who takes the time to dig a little further.

There are better, more cost-effective ways of reducing interior noise in an RV without resorting to expensive absorbers, especially when taking into account the very limited space available. I'll mention one of them that's pretty commonly known: "limp mass barrier" (typically, that is Mass Loaded Vinyl).

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Considering all these factors, Thinsulate or Low-E simply aren't the best or most cost-effective choices, even for vehicles with interior structures not conducive to the use of rigid foam board.

As you mentioned, it doesn't have to become a science project, and I really should not give away any of our IP anyway, so I've deleted every other post except my first one, which pretty much covered all the bases, without the excess technical explanation.

...
 

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GeorgeRa

2013 Sprinter DIY 144WB, Portland OR
………………………………….
And frankly, it's not in our best interest to give away any aspect of our IP that perform better at lower cost than what you've recommended in your related build thread....
Thank you for the extensive write-up, I tried to follow your points and got stuck on the last one. Are you saying that most of the stuff is not good except yours but you can’t share what it is because of IP?

George.
 

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