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

jghutchinson

New member
I have two rolls of reflectix sitting in my garage. After doing a little more research I am now deciding whether it is worth using it all. From what I understand, in order for reflectix or any radiant heat barrier to work for that matter... you need to have an airgap. If the reflectix is touching anything (like the interior metal of a vehicle) it will actually conduct the heat rather than reflect it. The ability of the reflectix to reflect the heat is negated by the simple fact that it is sitting behind the vans interior walls.

This video does a good job of explaining how reflective heat barriers must be used to work effectively:

https://www.youtube.com/watch?v=E1IwS0_lpBc


I would like someone that actually has a grounded understanding of thermodynamics to chime in on this rather than people that are simply regurgitating other people's potentially unfounded information.In an effort to reduce internal temperatures inside my van my initial plan was to use rattletrap buytl mats for sound deadening as the first layer on the interior panels, then lay reflectix on top of this. After thinking about this configuration in more depth I am now thinking that this will actually cause an increase of internal temperatures inside my van. Here are my thoughts...

The rattle trap is a dense buytl based mat with a reflective barrier on the back. The buytl mats density and general composition (like an asphalt road) will actually absorb heat in the form of sunlight that is hitting the van's panels. I am thinking that the bare metal of the van is actually more efficient at dissipating heat on its own when compared to the metal coupled with the rattle trap. Taking this further, if we then lay the reflectix on top of the rattle trap, all of this heat being absorbed by the rattletrap will simply be conducted and transferred across.

I am expecting people with argue that because reflectix is a double sided reflective material with the bubble rap in between, that this will act as a sufficient thermal decoupler but based on this video I am beginning to wonder if that is a load of bull.

I'm trying to avoid doing a lot of work that may actually be doing more harm than good. I've already purchased the materials, just not sure if I want to actually use them now.
 
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jghutchinson

New member
I see radiant barrier products sold for under slab installation, especially for use with a heated slab. My question is about air space being needed for reflectivity or emissivity or work. It seems that a pouring a cement slab over a radiant barrier pretty much takes all the air out of the situation. How are these products working? Thanks, Jim
You are correct, if the foil is on top or bottom of the insulation, then it will loose it's ability to be a radiant barrier since the aluminum layer is "sandwiched" between the insulation and the concrete or the insulation and the ground. Without an airspace, you cannot have radiant heat (you only have conductive heat flow in this circumstance) and if no radiant heat exists then you can't have a "radiant barrier." Don't waste your time or money putting any type of foil insulation under a slab. I'd go with a foam board or something that can provide some extra R-value.
 
In an effort to reduce internal temperatures inside my van my initial plan was to use rattletrap buytl mats for sound deadening as the first layer on the interior panels, then lay reflectix on top of this.
I'll leave the Reflectix debate to others, but I'll comment on the Rattletrap.

Although you are saying the Rattletrap will be applied to the interior panels, I am going to assume you mean the inside surface of the outer sheet metal. Products like Rattletrap have beneficial anti-resonance performance, but it reaches diminishing returns at about 25% coverage. Any coverage beyond that adds weight and cost, but will do little for further noise reduction. NCV3 vans already have reasonably good coverage of anti-resonant tiles.

The Rattletrap will be largely neutral as insulation. It has little/no R value, but your fear that it is converting sunlight to heat is not a concern. It will add thermal mass, which may increase the time required for your can to dissipate heat as it cools from day into night, but it won't create/transfer more heat to the subsequent insulation material further inboard (Reflective or other).
 

jghutchinson

New member
Thanks for your feedback and clarification on the rattletrap. I did indeed mean that I would be applying it to the inside surface of the outer sheet metal. That is good to know about the diminishing returns, I will use less and sell the remainder.

At this point, I think that only value insulation would provide to me for my use would be to dampen road noise coming into the cabin. My sprinter is being used as a surf mobile for the west coast of the United States, Baja Mexico, Central America and potentially South America down the line. My goal is to keep the cabin cool in the day vs keeping heat in to stay warm at night - am I doing more harm than good by trying to insulate the walls?

I am thinking now that I will focus on some good noise deadening materials to help mitigate road noise, do no insulation, and for cold nights I may just invest the money in a good down comforter / bed configuration / heater setup.
 
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I suggest you search the forums for 3M Thinsulate. It is engineered for the exact purpose you are pursuing: good noise absorption and reasonable thermal insulation. Its easy to work with.

Hein (forum member) sells it on eBay (search ebay for SM600L ). Its not cheap, but if you were considering full coverage of Rattletrap, it should be within your budget. For sound control, its FAR easier to install than common foam/MLV/foam techniques, and cheaper. FWIW I did my entire 2014 144" Crew with a 40 foot roll (200 sq ft) which ~= $500 on eBay.
 

lazylnm

Member
I'm with Inertiaman concerning sound deadening matt applications. My '15 has matt applied to the middle of all the large panels. I plan to only treat the wheel wells.
I've also been mulling over the insulation install. My current thought is to install a non-woven plastic matt - Stuc-O-Flex has a drainage mat with a filter fabric applied, which I would rip off - against the inside of the vans walls with perforated reflective film over that. Thinsulate would be installed over that followed by a true vapor barrier. The drainage matt is 3mm thick and provides an airspace for the radiant barrier and a drainage path to the bottom of the walls and weep holes so that when moisture does condense on the inside of the van walls, it has a place to go. I know that the contact points between the drainage matt and radiant barrier will transmit convective heat, but having 75-85% radiant barrier is better than nothing. It's important to have a vapor barrier at the interior face of the wall with everything else permeable. Still in the planning stage and I may change my mind. BTW - I practiced Architecture for 30+ years and these are basic concepts we used in developing wall systems in damp climates of Seattle and SF.
Another idea I had the other day way to apply a radiant reflective film on the roof of the van This was an inspired by a post concerning a radiant heat reflecting window film. Just a wild a$$ idea at this point. Our van in dark blue metallic.
 
Rattle trap etc is Constrained layer Damping material. Look up sound deadener showdown and read his info about CLD. I think many people use it incorrectly. It is not a sound barrier, It is a damper that changes the resonance of vibrating panels. It can be used judiciously in small quantities with great benefit, but you reach apoint of diminishing returns if you over do it. Covering every inch of your van is not cost effective use of the material.

I used CLD in my previous van and just applied most of it in our Sprinter yesterday. It may be moot if you stuff walls with batt insulation, the batt will also dampen vibration, but I noticed a beneficial difference when I added CLD to the Previa after driving it for a while with just polyester insulation in the walls.

I just had a thread about reflectix. Yes, you need an airspace for it to be effective as a radiant barrier. If you can furr it out from your walls and provide an airspace, it will help reflect heat back to the shell rather than allow it into the interior. Call them!
 

rb3232

Member
I'm with Inertiaman concerning sound deadening matt applications. My '15 has matt applied to the middle of all the large panels. I plan to only treat the wheel wells.
I've also been mulling over the insulation install. My current thought is to install a non-woven plastic matt - Stuc-O-Flex has a drainage mat with a filter fabric applied, which I would rip off - against the inside of the vans walls with perforated reflective film over that. Thinsulate would be installed over that followed by a true vapor barrier. The drainage matt is 3mm thick and provides an airspace for the radiant barrier and a drainage path to the bottom of the walls and weep holes so that when moisture does condense on the inside of the van walls, it has a place to go. I know that the contact points between the drainage matt and radiant barrier will transmit convective heat, but having 75-85% radiant barrier is better than nothing. It's important to have a vapor barrier at the interior face of the wall with everything else permeable. Still in the planning stage and I may change my mind. BTW - I practiced Architecture for 30+ years and these are basic concepts we used in developing wall systems in damp climates of Seattle and SF.
Another idea I had the other day way to apply a radiant reflective film on the roof of the van This was an inspired by a post concerning a radiant heat reflecting window film. Just a wild a$$ idea at this point. Our van in dark blue metallic.
Rolls of aluminum tape might work on the roof. I was considering using aluminum tape in the low channels of the floor. I won't now that I have decided on foam that will fill the air gaps of the floor channels...
 

lazylnm

Member
Don't think that radiant heat will be much of an issue on the floor - you might get some heat if parked on hot asphalt but no direct sun. I'm planning on painting the painted floor with a DIY truck bed liner prior to adding insulation and plywood.
The link to the window tint I was reading about:
https://sprinter-source.com/forums/showthread.php?t=38242&highlight=ceramic
From my earlier post - I said I didn't worry about the convective transfer of heat between the drainage matt and foil - should be conductive transfer.
 

roblee

Member
A fact-based discussion of the effectiveness of various insulation materials is indeed needed. I'd propose asking some questions first; like, what do you want to do? Me? I want to slow down the heating process of the inside of my van as the day gets hotter in the summer. I want to slow the cooling process of my van in winter as temps get colder after sunset. I want my heater or AC to be able to make the inside comfortable regardless of ambient temp and to do that efficiently so as to use as little energy as possible. Insulation is one way to do this; however, insulation only delays the inevitable. Without applying energy (AC, furnace, etc), the temp inside a van will equal ambient in winter and exceed ambient in summer regardless how it's insulated if it sits long enough. This is a matter of hours, not days. So we can never make a van cooler or warmer by adding insulation. We can only make it easier to heat or cool while using a HVAC system or slow the process of homeostasis because the laws of thermodynamics dictate that our van "wants" to be the same temp as it is outside. Convection, conduction, and radiation are all factors and all should be considered for van insulation. The skin of a van is a very effective barrier to convective heat gain/loss. With the windows and doors closed it is essentially sealed, there is little air exchange, and some aspects of convection are reduced. One thing to consider regarding Reflectix: the leap of faith is that the micro thin layer of "foil" would have to be more "Powerful" than the steel of the van skin that is magnitudes denser and trying like all get out to radiate its stored energy into the van. No contest IMO. I'd like to hear from others and I'll review some more physics.
 

ddunaway

Member
jghutchinson.

Generally speaking there are 3 kinds of heat transfer: conduction, convection, and radiative heat transfer. Reflectix works by reflecting radiant heat. All surfaces are emitting radiant heat at all times. Hotter surfaces emit more radiant heat than cooler ones. The material of the surface also affect the amount of radiant heat. Without an air gap the aluminum of the reflectix will just conduct heat though the bubbles provide some insulation. Conduction is via direct contact and provides the fastest heat transfer. Aluminum reflects heat efficeintly but also conducts heat quickly (good and bad for insulation respectively). There are also some nuances of whether it is hot outside or inside and on which surface (facing inside or outside) you have the reflective layer.

Reflectix is cheap. I am using it in areas where I have extra space between the Thinsulate and the wall, for example the lower parts of the van where the space is thicker than the 1.75 in Thinsulate.

There are some areas where reflectix is good but it is probably not the main product to use for insulation. If you do not have an air gap you should use something else for that location.....
 
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roblee

Member
EPA and Florida Solar Energy Center have a lot of info on radiant barriers. Bottom line: A properly installed barrier in an attic of a home in the southeast US could realize a maximum reduction in yearly cooling energy use of 8-12%. These installs are for attics where the air space is very large, the ceiling is insulated, and the air space is VENTED (like all attics must be to prevent condensation. This is a big difference than a van application. ddunaway's use of reflectix seems appropriate; put it in areas where a little more insulation is needed.
 

jghutchinson

New member
My thought process is that if it is not being used as a reflective barrier then surely the money could be better spent on a product that works more effectively as a thermal barrier with a higher r value. For what you are getting in terms of how it is being used in the van conversions... a roll of bubble wrap would achieve essentially the same thing and save you a pretty chunk of change.
 

mofo989

Member
I used 3M Thinsulate covered with Tyvec Thermawrap which has a metalized reflective coating which increases R-value due to reflectivity, but remains vapor permeable. It's thinner compared to Reflectix, and achieves the air-gap requirement as mentioned.
 
I used 3M Thinsulate covered with Tyvec Thermawrap which has a metalized reflective coating which increases R-value due to reflectivity, but remains vapor permeable. It's thinner compared to Reflectix, and achieves the air-gap requirement as mentioned.
The Thermawrap products are interesting. You are referencing the "LE" version which, as you note, is sort of Tyvek with a metalized coating. But they also have "Thermawrap R5.0" which frankly seems a lot like Thinsulate but cheaper. Its hard to find online, but I see a Home Depot page that shows it about $1/sq-ft (though I couldn't seem to come up with a zip code that actually had availability).

$1/sq-ft for 1.5" R-5 hydrophobic polyester insulation might be a compelling alternative to Thinsulate, no?

EDIT: I see now that it seems unavailable in USA Home Depots, but it is stocked at Canadian Home Depot. $169 Canadian for 4'x40'.
 
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mofo989

Member
The Thermawrap products are interesting. You are referencing the "LE" version which, as you note, is sort of Tyvek with a metalized coating. But they also have "Thermawrap R5.0" which frankly seems a lot like Thinsulate but cheaper. Its hard to find online, but I see a Home Depot page that shows it about $1/sq-ft (though I couldn't seem to come up with a zip code that actually had availability).

$1/sq-ft for 1.5" R-5 hydrophobic polyester insulation might be a compelling alternative to Thinsulate, no?

EDIT: I see now that it seems unavailable in USA Home Depots, but it is stocked at Canadian Home Depot. $169 Canadian for 4'x40'.
Interesting product. It came out after I did my van. I see it is 1-1/2” thick... might work. I'd love to see a sample to understand how easily it can be folded and tucked into tight places like the Thinsulate. Thinsulate certainly is meant for acoustic damping and is intended for automotive, so it does have that going for it.
 
Interesting product. It came out after I did my van. I see it is 1-1/2” thick... might work. I'd love to see a sample to understand how easily it can be folded and tucked into tight places like the Thinsulate. Thinsulate certainly is meant for acoustic damping and is intended for automotive, so it does have that going for it.
I'm already committed to Thinsulate (about 50% installed with the rest to be finished next week) but I'll seriously consider the Thermwrap to fill out the lower walls, sliding door and other areas which the Thinsulate didn't fully fill.

It looks like it should be as easily manipulated as the Thinsulate, though the Tyvek will be a little stiffer than the black polyester scrim on the Thinsulate, which might be a good thing.
 

mofo989

Member
Yeah, a more durable scrim would be a nice benefit. I think you're onto something here! Too many people stick with the same old methods and technology... even RV up fitters using fiberglass... yuck.
 

SprintingDragon

New member
Rattle trap etc is Constrained layer Damping material. Look up sound deadener showdown and read his info about CLD. I think many people use it incorrectly. It is not a sound barrier, It is a damper that changes the resonance of vibrating panels. It can be used judiciously in small quantities with great benefit, but you reach apoint of diminishing returns if you over do it. Covering every inch of your van is not cost effective use of the material.

I used CLD in my previous van and just applied most of it in our Sprinter yesterday. It may be moot if you stuff walls with batt insulation, the batt will also dampen vibration, but I noticed a beneficial difference when I added CLD to the Previa after driving it for a while with just polyester insulation in the walls.

I just had a thread about reflectix. Yes, you need an airspace for it to be effective as a radiant barrier. If you can furr it out from your walls and provide an airspace, it will help reflect heat back to the shell rather than allow it into the interior. Call them!
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?
 

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