Van insulation... welcome to the most controversial topic since the creation of #Vanlife! After years of passionate debate, Internet experts still can't agree on the best insulation for DIY van conversions. Let's hit pause on the emotional debate and do it our way: with theoretical analysis and real-life follow up.
Table Of Content
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1- Jumping to Conclusion
We’re not fans of shortcuts and hasty decisions, but there you have it. After 2 winters of full-time vanlife at temperatures as low as -22F (-30°C) and up to 95F (35°C), we recommend insulating your van with:
Thinsulate
We personally used Thinsulate in our van. It has kept us warm, no mold, no bugs, since 2017. It’s SO easy to work with, and there are no chemicals added (as fire retardant or bug prevention). We and our van love it.
(Shipping to USA and Canada. USA orders are tax free and ship from USA warehouse. Canadian orders are subject to taxes and ship from Canadian warehouse.)
That being said: knowledge is power! Make your own conclusion about van conversion insulation by reading the whole thing below… 🙂
2- Theory
2.1- Heat Transfer 101
The goal of adding insulation is to combat heat loss. Heat loss happens because of heat transfer (a.k.a. heat flow). Heat is always transferred from warm to cool and continues as long as there is a temperature difference; a larger temperature difference means more heat transfer potential. There are 3 heat transfer mechanisms: Conduction, Radiation & Convection.
Conduction
- Conduction is heat transfer through a material.
Examples:
- A pot handle (see picture above!)
- A spoon in a hot cup of tea
- A metal van surface getting hot inside the cargo area on a sunny day
HOW:
Energy is stored in the vibration of atoms. More heat = more energy = more vibrations. The collision of atoms between each other transfers heat.
Insulating for conduction:
The more dense a material, the closer the atoms are from each other and the more they transfer energy to their adjacent atoms (by physically colliding with each other). Therefore:
Less dense materials are a better insulator for conduction.
Radiation
- Radiation is heat transfer through electromagnetic waves.
Examples:
- The sun
- A Mr. Heater Buddy (there is some convection too but it's mainly radiant)
- A van dash getting hot when exposed to the sun
HOW:
Any hot (or warm) object radiates electromagnetic waves and can heat up other objects at distance (and therefore lose heat themselves). Energy is transferred through the electromagnetic waves, therefore, thermal radiation can happen through vacuum (without the presence of matter).
Insulating for radiation:
A white shiny surface is poor at absorbing and radiating heat. It is, therefore, a good radiant barrier.
Convection
- Convection is heat transfer through fluid (or gas) movement.
Examples:
- Hot air rising above an intense heat source (i.e. electric heater); Cold water falling towards the bottom of a lake
- A vehicle ventilation system (hot/cold air travels with the air being pushed by the fan)
HOW:
Heat is “transported” from one part of a fluid (or gas) to another by the bulk movement of the fluid itself. Hot regions are less dense, so they tend to rise and are replaced by cooler fluid from above.
Insulating for Convection:
Insulating hollow structure (i.e. frames) and eliminating air gaps minimizes air movement and reduces heat loss through convection.
While heat transfer can be separated in to 3 separate mechanisms, heat loss normally implies all 3 of them together. For example, a hot cup of coffee:
- Heat is transferred from the liquid to the cup surfaces (conduction + convection from the circulation),
- From the cup to the air and objects nearby (convection+radiation),
- From the cup to the cold table underneath (conduction),
- Blowing on coffee to cool it down (convection).
- (Heat is also lost through evaporation -change of phase-, but that’s out of our scope).
2.2- R-Value
Insulation materials are good at resisting heat flow. To quantify how good an insulating material is and to allow easy comparisons between them, a neat dude came up with R-value.
R-VALUE
R-value denotes the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power. It is normally noted (for example) “6.5 per inch“, which means applying one inch thickness of the material will provide 6.5 R-value; applying two inches will provide 13.0 R-value; and so on. R-value takes into account all three heat transfer mechanisms (conduction, radiation, convection). R-value is determined with the ASTM C518 test (“Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus”).
2.3- Condensation and Moisture Control
Vapor Barrier or not?
The purpose of a vapor barrier is to prevent moist air (from inside the van) from migrating towards cold surfaces. The idea is that moist air from respiration, cooking, drying gear, etc. won’t reach cold surfaces, thereby eliminating condensation issues. However, if, for any reason, moist air makes its way past the vapor barrier, it would be very hard to dry that moist air because it would be sandwiched between two vapor barrier layers (remember that metal is a vapor barrier too).
Even if one could achieve the perfect vapor barrier (which is unlikely, sorry), there are paths for outside air (charged with moisture) to infiltrate, and there are potential leak points as well:
Therefore, we believe that moist air will inevitably come in contact with cold structure, so our approach is to let the insulation layers “breathe” (no vapor barrier).
Condensation and moisture is quite complex, there is much more to talk about… we think this article should help you understand the phenomenon and help you make a better informed decision about your insulation:
2.4- Thermal Bridges
A thermal bridge is a path of least resistance for heat transfer. In other words, it’s a path for heat to “cheat” your insulation and find a way around it. It normally occurs via conduction through a dense material (such as metal).
Take for example the following picture. We added Thinsulate pretty much everywhere, except on the frames and pillars where we will attach our structure (cabinets, etc.). All the exposed metal is considered a thermal bridge, and heat will flow through it around the Thinsulate.
To mitigate the thermal bridges, a thermal break is added. We added LOW-E (EZ-COOL) since it’s pretty resistant to compression (applied by the structure attached to the van’s frames).
That’s important, especially if you’re using 80/20 aluminum extrusions for your build (structure, cabinets, etc.). Indeed, attaching the 80/20 aluminum directly to the van metal creates excellent thermal bridges; as a result, the 80/20 inside your van will be almost as cold as the van metal!
2.5- Air Loops
Hot air is less dense, so it tends to rise and be replaced by cooler air from above. That’s called an air loop and it’s a phenomenon that happens in non-insulated, hollow structures, like in the frames and pillars. So, to the question: “Is it worth shoving insulation inside frames knowing heat will find a way around (thermal bridges)?” We think it’s worth it. The total heat loss of your van is the sum of all the small pieces and bits… It all adds up!
3- Van Insulation Materials
At this point, we’re still on our quest to find THE BEST van insulation material… But in order to find out, let’s review our different options:
Thinsulate
- R-Value: 3.3 per inch.
PROS
- Very easy to install
- Hydrophobic (doesn't retain moisture)
- Doesn't off-gas
- Doesn't lose fibers and not itchy
- Good noise insulation
- Can be stuffed in hard-to-reach places
CONS
- More expensive
Bottom line: it’s a popular tried-and-true product that gives an added value to higher-end builds.
Polyiso Rigid Board
- R-Value: 5.6 per inch at 75F, 5.0 per inch at 15F.
PROS
- Impermeable to water vapor.
CONS
- R-value decreases substantially at cold temperature.
- Creates air gaps on funky surfaces (which is mostly the case in vans) = water traps.
XPS Rigid Board
- R-Value: 5.0 per inch at 75F, 6.0 per inch at 15F.
PROS
- Provides more reliable thermal performance than Polyiso.
- Impermeable to water vapor.
CONS
- Creates air gaps on funky surfaces (which is mostly the case in vans) = water traps.
- Maximum service temperature: 165F. (a darkly painted roof will get hotter than that in the sun! source: phys.org)
Spray Foam
- R-Value: 6.5 per inch.
PROS
- Conforms to curved surfaces.
- Impermeable to water vapor.
CONS
- Can distort the van panels if applied in thick layers.
- Messy to apply.
- Will block mechanism if no precautions are taken (e.g. doors).
- Some body shops won't do repairs if spray foam was applied.
Rockwool
- R-Value: 3.0 per inch.
PROS
- Easy to install
- Hydrophobic (doesn't retain moisture)
- Doesn't off-gas
CONS
- Itchy
- Can release fibers
Reflectix
- R-Value: 1.0 per inch.
Once upon a time, someone decided to insulate his van with Reflectix and blogged about it. Then everyone started using it.
By now, we know Reflectix is a very poor insulator. And on top of that, it requires an air gap in order to be effective.
It’s a good option to make your own window covers (to reflect the sun), but we prefer LOW-E as it is more resistant to tear and doesn’t have that annoying foil noise.
Low-E (EZ-Cool)
- R-Value: ?
PROS
- No foil noise
- Resistant to pressure (when inserted between van and structure)
Low-E insulation (formerly EZ-COOL) is sold as a “radiant-barrier”. It doesn’t have much R-Value, but it’s convenient to use as a thermal break and for insulated window covers.
From Heros to Zeros:
Recycled Denim
- R-Value: 3.5 per inch.
Why we don't recommend it
It’s hydrophilic: it absorbs and retains moisture. People sometimes attempt to enclose it in garbage bags only to find out later that the bags are torn and the insulation is soaked or moldy.
Fiberglass
- R-Value: 3.2 per inch.
Why we don't recommend it
It’s hydrophilic: it absorbs and retains moisture. People sometimes attempt to enclose it in garbage bags only to find out later that the bags are torn and the insulation is soaked or moldy.
Lizard Skin and other insulating Paint
- R-Value: Negligible
Why we don't recommend it
By now we know that efficient insulation materials are low-density. A coat of paint is everything except low density…
The manufacturers don’t provide any data (i.e. R-value, etc.) to backup their claims; there’s probably a good reason why (it would be fairly easy to test and publish data).
According to this Scientific American article, the EPA does not recommend insulating paint: “We haven’t seen any independent studies that can verify their insulating qualities”. They noted some heat gain reduction on surfaces directly exposed to sun only, and that “the reflectivity of the painted surfaces decline considerably with time”. It’s all about reflectivity, not insulation capacity. Are you really gonna paint the exterior or your van with insulating paint..?
Until independent studies show a benefit of insulating paint through standardized test, save your money and your time.
4- Our Insulation Strategy
Going from theory to real-life implies making compromises; there is no perfect solution! The best vanlife insulation is not just about R-Value, it’s also about:
- Ease of installation for the average DIYer
- Risk of messing things up (i.e. warped van panels)
- Condensation and moisture control
- Conformity to curved and uneven surfaces
- Material properties (i.e. maximum temperature, resistance to pressure)
With that in mind, here is how we insulated our campervan:
4.1- Floor
- XPS RIGID BOARD
To be efficient, any compressible insulation material (thinsulate, wool, etc.) must be fully expanded. As a result, they’re not ideal for floor insulation. On the other hand, XPS is an excellent insulator, provides a solid and flat foundation for our floor, is quite cheap, and is readily available at your local hardware store.
So, does it work in real-life? Definitely! We installed our Webasto so it blows hot air in our living space near and parallel to our floor; as a result, the floor is nice and warm, even in sub-freezing temperatures. But don’t get us wrong: the farther you go from the Webasto, the colder the floor gets. Cold air falls, remember? So even a perfectly insulated floor won’t be nice and warm all over unless it’s heated somehow. No, we don’t think a radiant heated floor is necessary (but could be a nice luxury); a pair of slippers is just fine and much more energy efficient!
We chose XPS Rigid Board C-200 to insulate our floor. The C-200 is rated 20PSI capable; human footprint = 16 PSI.
Here are our layers from bottom-up:
- 1/2″ thick XPS (to fill the corrugations)
- 1″ thick XPS
- MLV -not shown in the picture- (noise insulation, but we’d skip that layer if we had to start over)
- 1/2″ thick Plywood
- Vinyl Flooring -not shown in the picture-
We documented EVERYTHING about our floor installation here (insulation, sealing, bonding, plywood, vinyl, etc.):
4.2- Walls, Ceiling, Overhead cabin & Sliding Door
- THINSULATE
Installing Thinsulate insulation in a DIY conversion is a piece of cake: there’s no mess, no risk of messing things up, it’s not permanent, and it’s easy to work with. You’ll be all done in a weekend. Here is how it goes:
- Cut Thinsulate to size (using tailor scissors)
- Apply 3M 90 spray adhesive to the van wall and on the white face of the Thinsulate
- Wait 30-60 seconds for the adhesive to become tacky
- Press the Thinsulate against the wall
- That’s all!
How does it perform in real-life? Since we moved full-time in our van (2017), we’ve had everything between -22F (-30°C) and +95F (+35°C), and we’re in a good position to say it’s a tried-and-true van insulation material. If we had to build another van, we’d use Thinsulate insulation again without any hesitation.
We documented EVERYTHING about the installation of our Thinsulate insulation (walls, ceiling, overhead cabin storage, sliding door, etc.) in the following article. We also have a calculator to help you find out how much insulation to purchase:
- LOW-E
We covered all the remaining exposed metal and about 50% of Thinsulate surfaces with LOW-E insulation; this is to create thermal breaks and add some radiant barrier. We didn’t completely cover the Thinsulate in order to let it “breathe” (the LOW-E acts as a vapor barrier). As usual, we documented the whole thing:
4.3- Windows
- DIY Insulated Window Covers
You can spend a lot of money and time on the best insulation, but remember that glass is an excellent heat conductor (in other words, a horrible insulator). You can make cheap & dirty Reflectix covers to reflect the sun in summer, but if you are skiers like us, you will want something that performs better… To minimize heat loss during winter, we made insulated window covers out of low-e + thinsulate + fabric. They make a HUGE difference in sub-freezing temperatures, and they’re just plain essential below 5F (-15°C). Here is how we made them:
5- On Second Thought
You can read our second thoughts in each respective installation article listed above. But to sum it up: we would choose exactly the same van insulation strategy if we had to start over! It has served us very well.
Want to know more about winter vanlife? Driving in snow, 4×4, FWD vs RWD, electricity, finding water, finding camp spots, etc.? We wrote a debrief after our first winter full-time in the van (and plan on updating it every winter):
Your pix show ezCool installed underneath the wood panel strips used later for affixing cabinets, wall covering, etc. Did you use the pre-existing holes to affix the wood panels + Rivnuts, and if so, how did you ‘mark’ their location before applying the ezCool?
I wasn’t sure if you either: 1. marked and ‘uncovered’ the holes as you applied the covering, or 2. just covered and later drilled new holes through the wood and the metal.
If I recall properly, we transferred the hole pattern to the wood, then inserted the EZ-cool + wood and poked through it.
Hello. 🙂
The van I purchased has black wall and floor liners. I noticed y’all said that you used XPS for the floor because it’s solid and flat. Since my van already has floor liners, do you think placing Thinsulate under the floor liners would work just as well?
Thank you!
How to remove kilmat that was installed by the previous owner on the ceiling? I want to add additional beam support to the ceiling of the van but, the the surface is covered in sound deadening kilmat.
Could you please give the unit of R value?
Hey! The unit of R-Value can is ft2·°F·h/BTU
Per https://en.wikipedia.org/wiki/R-value_(insulation)
Not sure if that answer your question?
It seems like there are a lot of types of Thinsulate that 3M makes, with the “classic type C” coming in with R values between 4 and 5 per inch rather than the R3.3/inch on the variants you listed. Was SM600L picked to balance with acoustic properties?
Type C thickness is only 0.83″, as opposed to 1.65″ for SM600L (after expansion). Taking that into account, you get more R-Value with SM600L 🙂
Super surprised no mention of Havelock Wool! R value of 3.6 per inch, and moisture/mold resistant. Any experience with it?
Personally I prefer Thinsulate.
There are too many downsides of Wool:
– Factory sprayed with chemicals for insect repellent (and fire retardant I believe).
– Smells.
– Finicky installation (can’t be glued to the metal surface, must use ropes and strings).
– Pack out with time and vibration and therefore looses its insulation properties (I’ve seen photos of wool all packed at the bottom, after years of use).
So I’d rather stick with Thinsulate. My 2c! 🙂
The smell doesn’t last.It goes away quickly. You need to take the “sagging” into account when installing it. Because it can be broken in small pieces, you can use it to insulate the ribs. The chemical used for it’s treatment is Boric acid. The fact that you cannot glue it like Thinsulate makes it more complicated to install though.
I used it for my conversion and I’m very happy with the result.
What If I don’t want to strip out the walls upolstery? I may decide down the road I do want to do Van Life full time. I can’t put the insulate over the upholstery using glue. Wouldn’t that ruin the upholstery?
No mention of Havelock wool?
Hey Isabelle and Antoine, So far so great on all of your research and work. This stuff is tremendously encouraging because I would be making it up as I go with out your help. Question with insulation, thinsulate or wool? I keep seeing ads for Havelock wool pop up in my IG feeds and I was just curious because I’m typically a sucker for this sort of thing. My name is Ryan, I’m in Denver and just inherited a 69′ Ford Econoline.
We prefer Thinsulate. It doesn’t absorb moisture, doesn’t smell (we had a few report that wool smell a bit like barn), and it’s super easy to install: https://faroutride.com/thinsulate/
cheers
I’ve been reading your comparisons for insulating your van. I see that you chose thinsolate. I realize most of your testing is for living in a van. I am going to use mine for transportation and want to really help with the sound proof and keeping the van cool in the hot weather while driving. I have purchased the Kilmat but wanted your opinion what I should use over that if anything.
Hi Antonie. I’m from México and here the weather isn’t as cold. What’s you’re advise for a weather at a range of 15 to 100 F ?
Btw thanks for all the info, it’s very helpful.
Same thing, Thinsulate. It works for hot or cold weather. I would definitely get a white color (or light color) van for Mexico and plenty of ventilation! 🙂
Great explanation of the way heat loss works. We’re living in the Netherlands Thinsulate isn’t available (import would almost double the price) what are you thoughts about next best thing to insulate van walls and ceiling? We are considering sheep’s wool.
Hey folks! I’m looking for ways to increase standing height in a mid-roof 2019 Transit 150. One idea is to cut out and raise sections of the headliner between the roof beams. But I’ll be doing a fair amount of winter travel so still need insulation up there.
So… Wondering what your thoughts are on using 1/2″ XPS on the ceiling, instead of thinsulate? The van is painted white, which [could / should] reduce risk of over-heating the XPS in the summer compared with dark-colored vans. Another thought would be to add a layer of sound deadening material (dynamat or similar) as a mild heat barrier, and install the XPS over that. My experience with XPS is that while it’s not terribly flexible, it’s flexible enough to conform to the curve of a van roof.
But let me know what you think. And thanks for all the info and thoughts you’ve already shared.
I would not suggest very much Dynamat on the ceiling. Its VERY heavy, so covering the whole ceiling with it is going to add a good 75-100lbs of ceiling weight. Just cover some of the middle of each panel and it will help dampen vibration that leads to road noise. It doesn’t actually block sound, just dampens vibration in the metal. 20% coverage will provide nearly the same noise reduction as 100% if you get the centers of the panels where vibration is most prominent.
XPS will work as a ceiling material. Its going to be a little difficult to avoid gaps and voids, but I’m considering doing the same on my van as well.
Bonjour, félicitation pour tous les informations que vous nous avez fourni, je regardais pour l’isolation que vous suggérez et il n’y a pas mention de l’armaflex, un produit anti moisissure, je me suis commandé 14 feuilles de 36 X 48 X 1/2(pouces) j’espère que j’ai fait un bon choix!
Armaflex is very much like neoprene, a closed cell foam rubber product of a different name. Armaflex is like the foam tubes you insulate your hot water pipes with. How hard sheets of it are to conform to the sides of your vehicle without leaving air gaps is important. It does have good at noise reduction, heat insulation properties, and repels water. Will it work??? Probably, but keeping it snuggly attached to the sides of your vehicle might be a problem.
Isabelle and Antione and all,
Thank you for all you have provided, it is quite impressive, learning so much. Just bought Ford van and have a blank canvas. I’m starting to plan insulation and sound deadening, may be getting carried away.
I got to a place where I want to apply on butyl sound deadener to inside metal, then on top apply Uxcell which seems to offer me added sound deadening, plus radiant barrier. Both of these are thin enough, why not add? Then put Thinsulate on top of all that. I know cost may be an issue, until I calculate I really don’t know. I am willing to compromise on noise reduction and pay a little more, but don’t want to get carried away. Can these products be expected to perform together in my example? After installing butyl then Uxcell, can I spray the adhesive on them that will be needed for thinsulate to put on top? What do you think about all this?
Hi Guys,
Thank you for putting together such a comprehensive guide for people getting into van life!
We live in Tromsø in northern Norway and have just purchased our first van, unfortunately for us Thinsulate is not available here (or in Europe in general) and the price to import is beyond all but lottery winners. We are going to use XPS on the larger areas but I’m unsure what to use for door cavities and and deeper spaces. Rockwool is available here but I’m obviously concerned about water vapour getting into it (we are NOT installing a vapor barrier). Is there any other alternatives you could suggest?
Regards,
Ryan Ennis
Hey Ennis,
For other which may see this. In Europe, we have access to Armaflex XG which works great at 19mm and is easy to cover all large surfaces with. Then some 9 or 6mm to cover all the beams etc.
Even with the 3mm stuff, I can feel it stopping heat transfer.
Hello guys,
I love following you and think you built an amazing van.
How did you insulate your wheel well? With thinsulate?
Thank you
Yes, we added a layer of Thinsulate on it.
Antoine
Excellent article. There’s a lot of information here, and I’m digesting it in anticipation of our upcoming build.
Question: what do you think of using Kilmat in place of LOW-E (EZ-COOL), as a thermal barrier? I know you ultimately passed on a sound-deadening layer in the flooring, but might this be a way to incorporate some anyway?
I haven’t found any hard numbers on Kilmat’s thermal properties (and the sites that talk about it and its competitors are very short on figures), but it occurred to y’all might have some knowledge.
Thanks
Kilmat is a sound deadener; we don’t know much about the thermal properties and we never considered it as insulation. Plus, it’s pretty heavy and screwing anything through it sounds like a challenge! Low-E insulation is the material we would still use to reduce the thermal bridges.
We have sound deadener on our walls and ceiling and we have a layer of MLV in our floor. The truth is that we don’t really see the benefits of it… Once the van is completed, it’s hard to tell if sound-deadening is really helping and if adding all that weight was really worth it knowing now that the van is almost at its full weight capacity.
Thanks much, I’ll incorporate that into the plans
No chemicals added? Everything. Is. A. Chemical. Including everything in the insulation.
Absolutely enjoy your detailed approach to all of this. Fascinated to know what your take is on this havelock wool everyone is talking about lately!