WARNING: VERY LONG. And searchable.
Okay, I spent several weeks doing a ridiculous amount of research about various van insulation options, and getting confused and frustrated many times in the process. I even went back to insulation theory 101 to try to sort out fact from manufacturer’s claims, and relevant factors from confounding factors in anecdotal evidence by end-users.
What follows is a summary of what I have found, NOT recommendations for what you should use. No one insulation has it all; there are tradeoffs and you need to pick what factors are most important to you. I am writing this in the hope it will help you make more informed choices without re-inventing the (research) wheel.
DISCLAIMER: All of what follows is from research into the scientific basis of insulation, manufacturer’s claims, and end-user reviews, NOT my personal experience. I haven’t tried most of this in a real-world environment. Also, I have no affiliation whatsoever with any of the products mentioned, and listing them here is not an endorsement; just providing info.
I will try to stick to facts and not represent my biases, though I realize this is fundamentally impossible. I have tried to fact-check everything here as much as I can, but some information I found is inconsistent or even contradictory, so errors may have crept in. And I am not responsible for your choices of insulation.
About heat transfer:
There are three types of heat transfer, and most types of insulation are only good at blocking one, maybe two. Which means it is good to combine two or three types of insulation to combat them all.
CONDUCTION: Is when two surfaces touch and exchange heat, like when you touch your van’s engine when it is hot, and the heat transfers from the metal to your skin upon contact and burns you. Or when you bolt something to the roof of your van, then the van gets hot and contact between the metal in the van and the metal in the bolt makes the bolt hot, which in turn transfers to the thing bolted to it.
RADIATION: Is when energy moves through space (literally outer space or within our atmosphere) in the form of a wave and heats an object. This is how your van gets hot in the sun. And how, when your van’s engine is hot and you put your hand near it, you can feel the heat even from a few inches away.
CONVECTION: Is when heat moves through fluids, including air and other gases. Like when your van has been cooking in the sun (radiation), that energy is transferred to the air inside the van and the hot air makes it unbearable inside (greenhouse effect).
Lots of insulation products like to throw around R-values as a measure of how good they are at slowing down the transfer of heat from outside to inside, or vice versa. There are a few reasons this number is always misleading:
R-value ONLY measures conductive heat transfer. NOT the other two. So a product like Reflectix, which only blocks radiant heat, cannot have an accurate R-value (despite their claims). Because of differences in testing, even stated R-values vary widely between products or the same product in different applications.
And those R-values are only accurate under the same exact conditions as when they were tested in the lab. Real-world uses can drop the insulation’s efficacy by a lot. For example, fiber insulation relies on having lots of air space in and around it, and just the act of installing it can compress it slightly (a gentle hand putting it in place) and reduce its R-value. The R-value may also deteriorate as the product itself ages, or if moisture creeps in, or if it shifts within the walls of your van as you rattle down the road.
Take R-values with a grain of salt.
On to the insulation types:
Listed roughly in order of commonality among van dwellers.
REFLECTIX AND SIMILAR: Reflectix (http://www.reflectixinc.com) is the brand name of the most common RADIANT BARRIER. Strictly speaking, radiant barriers are not insulators but heat repellers. They don’t keep the warmth in, they reflect the sun’s rays before they get inside your van, so you don’t have to cool it down as much because it didn’t get as hot in the first place. This is a big plus on sunny summer days. Radiant barriers are highly reflective materials, usually with a thin bubble layer sandwiched in the middle of two layers of aluminum-foil-looking-stuff. It is completely free of chemical irritants, has no VOCs, is safe to handle and pretty cheap. The big issue is that a lot of van dwellers install it improperly and completely negate its reflective effect.
Radiant energy by definition transmits heat through space, and so the reflective barrier needs to have some space on the reflecting side in order for the radiation to travel to it and rebound off. No space = no reflection. Even worse, if the Reflectix is in contact with the wall of your van, it not only doesn’t reflect the sun, but because it is in contact with the van, it becomes a conductor of heat and actually makes the inside of the van HOTTER. Not what you want. So when you put Reflectix in the van, it needs to have about a 1/2″ to 3/4″ gap of air on the reflecting side. It could be stapled or glued to a wooden frame, attached around the frame of the window (not pressed up against the window itself), or with some other spacer. If doubling the Reflectix, there needs to be a space between each layer to get improved performance.
Also, where you put the Reflectix, matters. Because the floor of your van does not receive any rays from the sun, there is little to no radiant heat, so there is no point putting a radiant barrier there. The roof receives by far the most sun, and the walls get some but not as much as you might think.
SOLID FOAM BOARD: This is technically called extruded polystyrene rigid foam insulation. It is a petroleum product, highly resistant to moisture, and hence mold, but over time, on the order of years, it will break down and begin to trap moisture. It is also resistant to bugs and small critters as it provides no foodstuffs. It is easy to cut to fit, light, needs no special handling to install (no respirators or the like), and is reasonably priced. However it does contain VOCs and other chemical irritants, including formaldehyde, and takes years to off-gas, which in a small space can be unpleasant. Common reported side-effects include headaches, insomnia, respiratory irritation, depression, etc.
STYROFOAM: This is a brand name of closed-cell extruded polystyrene. Has all the advantages and disadvantages listed above, but is cheap. As in potentially free. Sure, you can go to Home Depot and pick up sheets of the stuff, but you could also ask every store in your area and they’ll be happy to fork over as much as you want. Cut to fit using a sharp blade or hot wire and you have the exact same stuff you would buy in the store.
SPRAY EXPANDING FOAM: This is basically the same extruded polystyrene foam, but in a spray can. Same advantages and disadvantages as above, but because you can spray it, you can get it in all the little nooks and crannies that are hard to cut boards to fit. This means you can fill in all the air cracks to greatly improve insulation value. However it is practically permanent. Once it is sprayed in, it cures within a few minutes and, from that point on, is almost impossible to completely remove. Unless you get a can that unexpectedly breaks down over time and begins to turn to dust, but this could take years. Or weeks. One reason this might happen is if it is applied in weather that is too warm, cold, or moist.
FOAMULAR SOLID FOAM BOARD: Foamular (www.owenscorning.com) is a brand product by Owens Corning. This is the only extruded foam board that has very low VOCs and no formaldehyde, is made with about 20% pre-consumer recycled materials, and is green approved by the National Association of Home Builders (I’m not clear what their standards are). All the normal benefits of extruded polystyrene rigid foam board with less nasty off-gassing. Can buy from Home Depot online at only a little more than normal foam board.
WOOD PANELING: A common outer-layer that both insulates somewhat and has design qualities. A 1″ thick panel of wood has an R-value of approximately 1.5, so it is not a great insulator, but does provide some heat control extra benefit, and good moisture control. When treated with a stain or oil it can be highly moisture resistant, insect resistant, with low or no VOCs (could be more, depending on your stain), although most lumber processed today does include a formaldehyde treatment which will off-gas slightly. Look for formaldehyde-free wood at the lumber yard for a little extra money. Wood paneling is a little more expensive than foam board, but still in the medium price range, and reclaimed wood can be found for cheap or free. Installation does take a lot more labor, a jigsaw or table saw, and some basic woodworking skills, or at least a friend who knows how.
WOOL BATTS OR LOOSE FILL: This is wool that is usually below quality to make into sweaters and other consumer products. It is naturally highly insulating, wicks moisture away, is easy and safe to install, contains no chemical irritants, no VOCs (so no off-gassing), has a lower manufacturing burden than petroleum products (though the cleaning process does leave its own medium-sized footprint), and is reasonably priced. Combined with BORAX, by sprinkling the Borax over and in the wool, or diluting it in water and spraying it on, it claims to be insect resistant. Despite starting off moisture (hence mold) and insect resistant, after a few years many users report finding mold or burying insects or other critters in their wool insulation. It can also settle over time due to the vibrations of the moving van, leaving the bottom of your walls more insulated and the tops lacking.
DENIM BATTS OR LOOSE FILL: Made mostly from post-consumer recycled jeans, this is almost entirely cotton. Easy and safe to install, contains no chemical irritants, no VOCs, has a low manufacturing footprint, and medium R-values (about the same as fiberglass for the same thickness). This is not naturally moisture resistant, but is combined with other fibers and treated so they claim this is not a big issue, but end-user reviews suggest it can be. Like wool, after a while there could be moisture (hence mold) and insect issues, and it can also settle over time. And you need it to be pretty thick (3″+) to get those medium R-values.
WINDOW TINTING: Windows are a huge heat drain in winter and heat suck in summer. Sure, you can cover them at night, or permanently, but if you want to see out during the day, window tints and films can reflect radiant energy from the sun to keep your van cooler inside. There are new, non-metallic versions available that do not interfere with radio, cell or bluetooth signals, which can happen with some of these products.
The problem with traditional window tinting is that the darker the tint, the more it turns from a reflector into an absorber. The visible light that it blocks to prevent people from seeing inside is only one small part of the spectrum and the rest actually gets absorbed by the dark color, making it hotter inside. Look for a product that blocks full spectrum heat, measured in BTUs, not just UVs. One brand that got good reviews is XPEL Prime XR window film. (www.xpel.com/prime-xr/) It blocks full-spectrum energy and does not interfere with your devices. They even have an almost clear tint that still blocks many of the sun’s rays and is legal to put on windshields. This could make driving on a sunny day much more comfortable.
Now for a few uncommon or alternative options:
FIBERGLASS BATTS: This is used primarily in houses, but I looked into it anyway. It has a decent R-value if you can get it thick enough, but that will take 3″ to 4″ on each wall of your van. It is also likely carcinogenic, has lots of chemical irritants including formaldehyde, high VOCs, is not safe to install without protective gear, is moisture resistant only for the first few years and then it tends to develop major mold problems, but it is cheap and insect resistant.
BLOWN IN FIBERGLASS: Same advantages and disadvantages of the batts, except that it can get into more of the small spaces, because it is small and fluffy and gets everywhere, but that also means the little bits fly every-everywhere, and so do the carcinogenic particles (this is me betraying biased reporting).
ECOBATT: (www.ecobatt.us/eco_batt.html) This is a brand product from Knauf, a maker of fiberglass batting, and is a type of related glass wool fiber that is less dusty, less inhalable and therefore less likely to remain in your lungs for long. This is their answer to the health and environmental hazards of fiberglass. It is made of renewable organic materials, sand, and post-consumer recycled glass bottles with their proprietary ECOSE Technology, has a low manufacturing footprint, and is certified green. It has comparable R-values to, and is just as thick as, fiberglass batting. Like traditional fiberglass, when compressed it lowers the R-value.
STONE WOOL OR MINERAL WOOL: This is made from pouring molten lava or molten rock waterfall-stye, and then blowing high pressure air through the stream of lava so that it quickly cools into thin strands. These are then combined with slag and a few additives to make a wool-like substance or dense board. The result is a very good insulator, of which Roxul (www.roxul.com) is a common brand. Batts are around 3″ thick for R12 to R23 values. Medium price range, easy to install, there are particles that will cause itchiness, but much less so than fiberglass and when ingested they do not remain in the body for long, and is classified as not likely carcinogenic to humans. It does, however, use trace amounts of formaldehyde as a binder. It is fungi, bacteria, and water resistant but not waterproof, and tends to dry out quickly when it does absorb moisture. It also claims to be insect resistant though users report a variety of burying critters making nests in this in their home walls. It has a comparatively low manufacturing footprint and is made of partially recycled materials. As a bonus it is absolutely non-combustable below about 2150º F or nearly 1200º C.
CELLULOSE LOOSE FILL: (https://www.greenfiber.com) There are a few brands that make this, but Green Fiber is one of the leaders. This is most commonly used in house attics and walls, and is growing in popularity because the price is comparable to fiberglass but without the carcinogens. It is made of recycled newspapers, sometimes mixed with borax for flame retardant and mold retardant properties, has minimal or no VOCs, an R-value of 3.8, and because it is loose fill, will get in all the cracks and crevices of a van. It can settle in the walls over time, and produces dust during application, but there are no toxic chemicals in the dust and it is non-itchy. In house use it is normally installed by an industrial blower machine, available for rental from your local hardware store, but in the amount needed for a van, this may not be necessary.
THINSULATE: (www.3m.com/3M/en_US/thinsulate-us) This is thin batting that is primarily used for lining jackets and gloves, has low R-value, but is fairly cheap and free of chemical irritants, contains no VOCs, is easy and safe to use, but you might need a lot of it to get decent insulation. You can get a version that is made from 50% post-consumer recycled waste, and another version that is water resistant. I haven’t seen any end-user reviews of how well it worked in vans, so I have no idea about long-term moisture, mold, or insects. I only started to research it because I heard from at least two people who put it in their vans (don’t know how it turned out over time, though).
DYNALINER: This brand product (www.dynamat.com) is primarily marketed as a sound-deadener but also has very good insulation qualities against both heat and cold. The manufacturer has a few variants for different specific parts of your van, such as a floor pad, roof liner, and engine hoodliner, and the few end-user reports I could find about the insulating qualities specifically claim anywhere from “some” up to “50%” reduction in indoor temperature after the stuff was installed throughout the walls, roof and floor of the back of the van. It is made of butyl rubber foam, a form of vinyl rubber, not a petroleum product. It is considered “non-hazardous,” yet I couldn’t find anything specific about that either way, and also couldn’t find the MSDS. It is very thin, lightweight, weather resistant, waterproof, oil resistant, wear resistant, flexible, easy to install, and deadens noise and rattling to boot. It is also somewhat pricey.
MELAMINE FOAM: This is a type of foam that is often marketed as an insulation barrier or acoustic barrier (as well as fire retardants, fertilizers for crops, dinnerware, infant formula in small quantities, and sometimes illegally added to food products to improve its apparent protein content). It is thin, light, flexible, easy to install, and highly toxic when ingested, inhaled, or absorbed through the skin. Long term exposure to the odor is carcinogenic.
AUTO CARPET: This has a very low R-value (around 1.1 to 1.5, with a value of 1 equivalent to ambient air temperature) so that any insulation benefit it provides is more of a happy bonus. It is meant to collect dirt and moisture and does a good job at both, for the better and the worse. It also traps smells apparently, according to several board comments, so be careful when cook pungent meals around it. It is fairly cheap, flexible, non-hazardous, you can get it in post-consumer recycled varieties if you want, and is easy to install. It is useful for hard to insulate areas around doors and siding, and of course to cover floors or other insulation so your home looks nicer.
DUCT AND WATER TANK INSULATION BLANKETS: Products like those made by Frost King are specifically designed to insulate house air ducts, hot water tanks, and provide general weather striping around all air gaps in the house. These are usually very good insulators, are easy to install, some come with an aluminum backing for an extra thermal barrier and some don’t. They are reasonably priced per square foot, but you will have to buy a lot of small packages to cover the entire surface area of a van. They are usually made of a compressed fiberglass, which means formaldehyde and other VOCs just like the fiberglass above.
CORK UNDERLAYMENT: (https://amzn.to/33VzIFe) While not sold specifically as insulation in the US, cork has been used as rigid insulation in Europe for decades because of its excellent thermal insulation properties; it is often sold as trivets for putting hot pans on because of this. Its most common use is as wine stoppers, which testifies to how it does not grow mildew when wet. Cork is 100% natural and rapidly renewable as defined by the LEED Rating System. The majority of the world’s commercial cork is sustainably harvested from federally protected trees in Portugal. It has no VOCs, is naturally fire-retardant, has excellent sound-deadening properties, and when sold as rigid insulation usually has an R-value of around 3.6 to 4. It can be found in rolls as underlayment for flooring, and as such is in the medium price range and readily available at most hardware stores and online.
AEROGELS: Aerogels (https://en.wikipedia.org/wiki/Aerogel) are a relatively new product category, and are currently marketed mostly for industrial and commercial use because they are so incredibly efficient and so incredibly expensive. (www.tinyurl.com/gv8qmwx) As insulation, it is basically a super-dense fibrous blanket that comes in 5 mm or 10 mm thicknesses and has amazing R-values. It can insulate pipes up to 1000 degrees F, or your van, using very little space. It is flexible, breathable, light, easy to work with and safe to install, hydrophobic (moisture repellant), has no insect problems, and ultra low VOCs. It is also upwards of $6/sq ft. and available from very few distributors for consumer purchase. Here’s one that will sell it to you under the product brand Spaceloft: www.tinyurl.com/jytdaa3. I’ve haven’t heard of anyone using this in their vans yet, but am intrigued.
REFLECTIVE PAINT: This is sold as either pre-mixed paint or a paint additive that you can mix into whatever paint you choose. The premise is that the surface is highly reflective so that a portion of the radiant energy from the sun bounces off instead of heating up the van. (Basically liquid Reflectix.) Some of these paints work better than others, and some are no better than just painting your van white (which, by the way, also reflects a fair amount of radiant heat). Look for one that is “cool roof certified” by the Cool Roof Rating Council. (www.tinyurl.com/jgfuuyo) Nutech Paints has the best 3-year cool roof rating, and you can get it in a variety of colors. (Corporate: http://www.nutechpaints.com A US distributor: www.nutechpaintsca.com)
INSULATING PAINT: Okay, brace yourself for controversy. I’ve spent countless hours trying to sort fact from urban myth from marketing hype. Here is my conclusion: I don’t know.
The premise is that this is normal paint that contains tiny, hollow ceramic beads or vacuum filled nano particles or micro bubbles (there are a few versions). Supposedly this was developed originally for NASA to shield the parts of the rockets and boosters that bore the brunt of the scorching heat of hurtling through the atmosphere. They certainly had to use something for that, but some claim it was an unrelated carbon compound. NASA itself agrees that Insuladd (www.insuladd.com) brand insulating paint is a NASA-spinoff technology, so maybe that part is true. But it is also true that there are a number of manufacturers out there who claim they are selling this stuff (either pre-mixed in white paint or as a paint additive), and who are clearly frauds. There are tons of customer complaints to the BBB about these hoaxters, and their paints do not hold up to simple DIY tests.
However, just because some of them are frauds, doesn’t mean the technology isn’t out there. But even the most reliable-looking sources describe how it works as a way to reflect heat energy before it enters the painted object, so I would personally classify this as one version of a RADIANT BARRIER, NOT AN INSULATION per se.
There are also a lot of happy customers leaving reviews describing their houses feeling cooler and reporting energy savings in the summer, though these types of paints are almost exclusively white, and I am not sure how much those improvements were due to the reflective quality of the ceramic particles or micro bubbles, or how much was due to simply painting their roof white (itself highly reflective) instead of the much darker original color or exposed metal which would both absorb heat. There is a ton of undisputed research to the effect that if everyone painted their house roof white, it would result in gargantuan energy savings and reduce “heat island” effects in cities.
The idea is enticing, however, I am unconvinced at this point. If you try it, I’d love to hear how it turns out.
A few other considerations:
ACOUSTIC FEATURES: Many of the above insulation manufacturers tout their sound-deadening properties as a feature of their products. However, ALL of the above insulations have sound-deadening properties. This will be true of anything you put against the wall of your van.
Try this at home: find a piece of sheet metal (like the side of your vehicle) and rap it once with a knuckle. Listen to how it rings. Now lay one hand on the same bit of sheet metal and rap on it again. Notice the difference in sound? This happens because the sound waves are partially absorbed by your hand (or anything else you put against it). Some materials absorb sound waves better than others, but for me this is just an added bonus, not a reason to choose one insulation over another (yes, I’m betraying bias again) and that is why I did not include it in the reviews above.
FIRE RETARDANTS: Similarly, I did not include their fire-retardant qualities because they ALL have at least decent fire retardant abilities, as required by law to be sold as home or auto insulation.
AIR GAPS: Air gaps are the enemy of insulation. Do your best to seal every crack, hole, and gap, especially around windows, vents and doors, so as not to let condensation build up on any metal surface, or let your precious heat escape in winter or let it get in during summer.
SOLAR PANEL CONSIDERATIONS: While not strictly speaking insulation, I think it worth mentioning that solar panels can either help or hinder your other insulation efforts. Black solar panels absorb solar radiation (duh), and when attached to the roof of your van directly, conduct some of that energy to the van body and from there to the inside of your van, partially defeating any radiant barriers or insulation you have installed on the inside of the roof. When the panels are attached slightly above the roof (not in direct contact) by mounting brackets or a roof rack, it creates an air space which still allows some radiant heat through, but far less than the conductive heat from full contact. Plus it provides some shading from, and absorption of, some of the radiant heat that would be hitting the van if the panel were not there at all. Some of it will pass right through the panel no matter what and go into the van anyway, but you can minimize this.
SAVING MONEY: There are lots of people who have extra insulation leftover after big projects and are putting the remnants up for sale or free on Craigslist, Freecycle, eBay or similar sites. Since a van doesn’t require lots of materials, their scraps might be enough.
MAKING A CHOICE: Your van, climate, tolerance for chemicals, how long you want the insulation to hold up, etc. is different from mine and everyone else’s, so I provide the above in the hopes you can make sense out of the options out there to make the best choice for YOU.
Which is why I’m not making any recommendations, except this one. You might seriously consider using a combination of insulating materials to block the different types of heat, for example, a radiant barrier and other insulation, to give yourself a better overall experience.
Hope this helps.