Insulating Your Van: Everything You Need to Know for Your DIY Van Build

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Insulating Your Van: Everything You Need to Know for Your DIY Van Build

Van Build Insulation

This post may contain affiliate links. Learn more >>

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If you want to stay comfortable in your van no matter the weather, you need to insulate. Insulation is one of the most important steps of any van build, and it pays to take the time to do it right. There’s also a lot of confusion and debate over the best way to insulate a campervan, and it can be tough to wade through all the opinions and figure out what to do.

When we were planning our build, we had all kinds of questions about insulation:

What’s the best material to use? How do we go about installing it? Do we need a vapor barrier? How much should we budget? What other questions should we have that we don’t even know to ask?

In this post, we answer the questions that come up most frequently about insulating a van for vanlife. We also take a deep dive into commonly used insulation materials, their pros and cons, and whether you should use them. Finally, we dig into our recommendations and go through step-by-step installation instructions.

This post should cut through some of the confusion you may have about insulation, so you can get your van built and get out there on the road!

TL;DR: There’s a ton of great info on insulation in this post (including helpful charts and graphics!) But if you’re looking for a quick answer or just want to see our recommendations, click here to skip ahead to the bottom line. 

Heat Transfer and Insulation: What You Should Know for Your Van Conversion

So why do we need insulation and what exactly does it do for us vandwellers? To answer these questions, it helps to understand a little bit about how heat transfer works.

There are three types of heat transfer: radiation, conduction, and convection.

heat transfer methods

Radiation is heat transferred through air or a vacuum – think of the heat radiating from the sun, passing through the atmosphere, and warming your skin.

The biggest sources of radiant heat in your van are the windows, which allow sunlight to pass through and heat the inside. This can be nice in the winter, but absolute hell during a hot summer day. Reflective window coverings deflect radiant heat away from the van and keep the inside much cooler. You can also use reflective surfaces inside your van to help retain heat during cold weather.

Conduction is heat transferred through solid surfaces – think of when you touch a hot cast iron skillet and burn your hand.

When the radiant heat from the sun warms the metal body of your van, the heat is transferred inside through conduction. When it’s cold, heat also transfers out of the van via conduction. We can slow this process of heat transfer by insulating the walls and ceiling.

Convection is how heat moves through a liquid or gas (like the air in your van) – think of warmer air rising to the ceiling while cooler air sinks to the floor.

Because of convection, the heat inside your van naturally rises upwards. Having thicker insulation on the ceiling helps keep this heat inside during cold weather. And when it’s hot, a ventilation fan can suck out the warmer air near the ceiling while pulling in cooler air from a floor vent or cracked window.

Insulation slows the rate of heat transfer into and out of your van, which makes it easier to maintain the temperature you want.

A well-insulated van is easier to heat and cool, stays warmer in the winter, and won’t heat up as quickly in the summer (although, preventing radiant heat from getting in through the windows is even more important in hot weather).

Every insulation material has an R-value, which is a measure of the material’s Resistance to heat transfer. The higher the R-value, the better it’s able to resist heat transfer via conduction.

A thermal bridge is an area that has greater thermal conductivity than the materials around it, providing an avenue for heat to pass through.


When you stuff insulation between your van’s frame ribs but don’t do anything to the ribs themselves, the frame then becomes a thermal bridge. Heat can conduct inside your van through the exposed frame much more easily than it can through the insulated areas. This thermal bridge reduces the overall effectiveness of your insulation, since heat can go around it to a certain extent.

Some insulation is always better than no insulation, and an insulated van with some thermal bridging is much more resistant to heat transfer than a van with no insulation at all.

Insulating inside your van’s hollow frame can help reduce the effect of thermal bridging. If you spend a lot of time in very cold weather, it might be a good idea to put up thermal breaks, which are basically non-conductive materials (i.e. insulation) placed in the pathway of a thermal bridge to block the flow of heat. If you put up additional insulation on top of your van’s ribs, that would be a thermal break.

Now that we understand how basic heat transfer works, let’s take a look at the insulation materials we can use to slow it down.

Super Detailed Rundown of Common Insulation Materials (Plus an Informative Chart!)

common van insulation materials by @drivingdarlene

Photo by @drivingdarlene

There are a ton of different insulation materials available, from standard building insulation to experimental space-age compounds. Wading through them all and trying to decide what’s best for your van conversion can be a daunting task – which is why we’ve done that for you.

While there are a lot of options out there, not all of them are good choices for insulating a van. Good van insulation needs to have the following:

  • High R-value per inch. Space is at a premium inside a van, and you want to insulate with materials that will do the most in the least amount of space.
  • Bang for your buck. There’s no need to spend thousands (or even hundreds) of dollars insulating your van. Some materials may work well, but cost more than your actual van did. On the flip side, some materials are dirt cheap but have a host of other issues. The best insulation materials do their job effectively and are also friendly to your wallet.
  • Able to withstand vibration. Unless you’ve got your van up on cinder blocks in the front yard, you’re probably driving it all over the place all the time. Driving causes a lot of vibration inside your van, and your insulation needs to be able to take it without falling apart.
  • Resistance to moisture, mold, and mildew. Either the material is impervious to moisture (like rigid foam board or spray foam) or has moisture control properties and natural mold resistance (like Thinsulate or sheep’s wool).
  • Non-toxic. You don’t want harmful gases or microscopic particles from your insulation filling your (very small) living space. Bonus points if the insulation is produced in an environmentally-friendly way.

But how do we directly compare different insulation materials when they all come in different thicknesses and square footage and R-values?

With a spreadsheet, of course! The chart below compares the R-value per inch and relative cost of some of the most common and most talked-about campervan insulation materials out there.

MaterialR-Value / Inch*Cost for R-1**Recommended Use***
ReflectixR-4.4$0.39Windows, Cavities
Polyisocyanurate (Polyiso)R-6.0$0.12Walls, Ceiling
Extruded Polystyrene (XPS)R-5.0$0.12Walls, Ceiling, Floor
Expanded Polystyrene (EPS)R-3.9$0.10Not Recommended
Closed Cell Spray FoamR-7.0$0.27Gaps & Fill-In, Adhesive
Fiberglass BattsR-3.7$0.03Not Recommended
Rock Wool BattsR-4.3$0.64Door Panels
Denim BattsR-3.7$0.31Door Panels
Sheep's Wool BattsR-3.7$0.14Walls, Ceiling, Doors
3M ThinsulateR-3.2$0.53Nooks & Crannies
Lizard SkinN/AN/ANot Recommended

* Nominal R-value / Unit Thickness     ** Amount you would need to spend to insulate 1 square foot to R-1.     ***  See below for details on recommended use.     Want to see where these numbers are coming from? Click here to view our source spreadsheet!

Looking at this chart, there are a few clear winners that both insulate well and are cost-effective. But every type of insulation may be good for some applications and not so good for others. Below, we dig a little deeper into each of these materials and their recommended uses.

Reflectix (and Other Radiant Barriers)

reflectix van insulation by @karakarakaradise00

Photo by @karakarakaradise00
  • R-Value Per Inch: R-4.4
  • Cost for 1 ft2 of R-1: $0.39
  • Where to Buy: Most big box hardware stores

Reflectix is thin bubble wrap with a reflective coating on each side that acts as a radiant heat barrier. It’s widely recommended for diy van builds, but it’s also widely misunderstood.

If you’ve watched any van build Youtube videos, chances are you’ve seen someone insulating their van by gluing Reflectix up against the metal walls with paneling right on top of it. This is just plain wrong.

The fact is, Reflectix is primarily a radiant barrier. It’s very effective at reflecting radiant heat, but this goes out the window as soon as you put something on top of it.

Since radiant heat only travels through air or a vacuum, there needs to be at least a ¾” air gap next to the Reflectix for it to have any effect at all as a radiant barrier. When you put Reflectix directly against your van’s walls, you’re now dealing with conduction and the R-value comes into play.

While Reflectix does have an R-value, it’s very minimal (about R-1), and it’s very costly for what you get. Other materials will give you much more R-value for much less money.

That said, Reflectix has its uses. Because it’s so good at reflecting radiant heat, it’s awesome as a window covering. On a hot day, shield your windows with Reflectix (or another radiant barrier like EZ-Cool or Insul-shine, or an Eclipse Sunshade) and you’ll notice a dramatic difference in the amount of heat getting in. It also works well for insulating large cavities like the interior of door panels, because there will naturally be an air gap that allows it to hold heat in.

VERDICT: Recommended for window coverings and large cavities. Reflectix is great as a radiant barrier, but you’re wasting your money if you put it behind your walls. There are much more effective and much less expensive insulation materials out there that have a higher R-value per inch.

Polyisocyanurate (Polyiso) Foam Board

polyiso van insulation by @adventurevanfor9

Photo by @adventurevanfor9
  • R-Value Per Inch: R-6.0
  • Cost for 1 ft2 of R-1: $0.12
  • Where to Buy: Most big box hardware stores

Polyisocyanurate (or polyiso for short) is a rigid foam board insulation that’s widely used in green building applications and van builds. It has an impressive R-value per inch at R-6, it’s fairly easy to work with, and it’s affordable.

Polyiso typically comes foil-faced on one side, which both acts as an effective vapor barrier and provides a radiant heat barrier if you install it with an air gap.

Polyiso is completely non-toxic and doesn’t off-gas anything harmful. It’s also much more environmentally friendly than XPS foam board, but not nearly as environmentally friendly as sheep’s wool insulation.

VERDICT: An affordable and effective choice for insulating your van. We used polyiso in our first van build, and we highly recommend it – especially for budget builds. With polyiso, you get great bang for your buck and even better R-value per inch. And when you’re building a van, R-value per inch is supremely important.

The downside to using polyiso (and foam insulation in general) is that proper installation is very important – you don’t want to create accessible air pockets behind your insulation where moisture could get trapped.

You can find polyiso at most big box hardware stores these days, but it can still be a bit tougher to find than other types of insulation.

Extruded Polystyrene (XPS) Foam Board

xps van insulation by @battlestar_galactivan

Photo by @battlestar_galactivan
  • R-Value Per Inch: R-5.0
  • Cost for 1 ft2 of R-1: $0.12
  • Where to Buy: Any big box hardware store

Extruded polystyrene (XPS) is another type of rigid foam board insulation that’s also widely used. You’ll recognize it as the big pink or blue foam sheets at the hardware store (the pink stuff is branded as Owens-Corning Foamular).

XPS has very good R-value per inch at R-5, and is also impermeable to moisture. Another benefit is its high compressive strength, making it ideal for floor insulation. You can even use it to build lightweight cabinets for your van!

Although XPS is slightly cheaper than polyiso by the sheet, it also has a slightly lower R-value per inch. And it’s not at all environmentally-friendly. XPS manufacturers use HFCs (hydrofluorocarbons) in its production, which are incredibly harmful greenhouse gases that are much worse than CO2 in their effect on global warming. XPS manufacturers say they will stop using HFCs by 2020.

VERDICT: Use this if you can’t find polyiso. Because of its high R-value per inch and fairly low cost, XPS is an excellent choice for van insulation. Even if you use polyiso as your primary material, we recommend using XPS under your floor because of its higher compressive strength.

There’s also some research that shows XPS performing better than polyiso in extreme cold, so if you regularly spend time in very cold weather this may be your best option. That is, if you can get over the unfortunate environmental costs.

Expanded Polystyrene (EPS) Foam Board

eps van insulation by @vinnieandthelynchs

Photo by @vinnieandthelynchs
  • R-Value Per Inch: R-3.9
  • Cost for 1 ft2 of R-1: $0.10
  • Where to Buy: Any big box hardware store

Expanded polystyrene (EPS) is another type of foam board insulation. It’s basically the same stuff as typical styrofoam.

EPS works fine, and it’s super cheap. But it contains a lot of air gaps that allow moisture to penetrate, degrading the material over time. It also won’t stand up to vibration as well as polyiso or XPS, and generally isn’t as durable.

But, on the plus side, no HFCs are released in its production, so it’s relatively environmentally friendly!

VERDICT: If you’re going with foam board, there are much better choices. Although EPS is cheap and works fine as insulation, it has a lower R-value per inch and degrades over time – especially when exposed to the vibrations of a van. Polyiso and XPS have much higher R-value per inch, can stand up to vibration, are moisture impermeable, and are generally far better choices.

Closed-Cell Spray Foam

spray foam van insulation by @karastein

Photo by @karastein
  • R-Value Per Inch: R-7
  • Cost for 1 ft2 of R-1: $0.27
  • Where to Buy: or most big box hardware stores

Closed-cell polyurethane spray foam comes in two varieties: the big spray kits that professionals use to insulate houses, and the smaller cans of spray foam like Great Stuff.

Spray foam insulation has the highest R-value per inch at R-7, and when installed correctly forms an impermeable vapor barrier that can shield your van’s metal walls from condensation. It also works as a sound dampener.

But, spray foam kits are rather expensive – foaming your entire van would cost upwards of $400. Installation can also be pretty intimidating, not to mention messy. It could end up being a total nightmare if you do it wrong.

Canned spray foam like Great Stuff is fairly inexpensive, and does a great job at filling gaps, cracks, and hard-to-reach areas like your vehicle frame.

VERDICT: Skip the big kits, but use Great Stuff to fill gaps. Spray foam is great insulation, and if you’re okay with the extra expense and installation process then it can be a good choice. But rigid foam board is much cheaper, easier to work with, and nearly as good at insulating.

However, Great Stuff canned spray foam is perfect for gluing up foam boards and insulating between them, as well as filling all those little gaps and cracks.

Fiberglass Batts

fiberglass van insulation by @sprinter_adventures

Photo by @sprinter_adventures
  • R-Value Per Inch: R-3.7
  • Cost for 1 ft2 of R-1: $0.03
  • Where to Buy: Any big box hardware store

Fiberglass is the most widely-used insulation in houses because it’s super cheap and it works. It stands to reason that it would work well in vans also.

But its only real upside is that it’s cheap. Fiberglass has a fairly low R-value per inch, meaning you need more thickness to get the same insulating value as foam board. It’s also toxic and a pain to work with. It will make your skin itch, and you do NOT want to breathe it in.

Fiberglass soaks up moisture, which you definitely don’t want sitting behind your walls. It also degrades over time, and may fall apart and release harmful particles with all the vibration of driving around in your van.

Because fiberglass is so cheap, it’s definitely an attractive choice for bare bones van builds on a tight budget. It’s also good for stuffing in door panels and jamming into your vehicle frame (that’s what we did). Just make sure you have it fully sealed off from the living space.

VERDICT: Toxic and a pain to work with, but it can be useful in some cases. We generally don’t recommend using fiberglass in your van, but we do recognize its utility as a budget material. It’s also a way to cheaply insulate your door panels to R-13 or higher.

Rock Wool Batts

rock wool van insulation by @spritesizedadventures

Photo by @spritesizedadventures
  • R-Value Per Inch: R-4.3
  • Cost for 1 ft2 of R-1: $0.64
  • Where to Buy: Most big box hardware stores

Rock Wool (also called mineral wool) is a semi-rigid batting material made from recycled stone spun into thin fibers. It’s very common in Europe and Canada, less so in the US. Rock wool has a higher R-value per inch than fiberglass, and its rigidity makes it much more durable and easier to work with.

But, it’s also a whole lot more expensive, and the R-value per inch is still a lot lower than foam board. And, like fiberglass, installation can be a very itchy process. Again like fiberglass, you will want to wear protective clothing and a face mask whenever you work with rock wool. Inhaled rock wool slivers can become lodged in your lungs, and there have been some indications that this can lead to health problems.

VERDICT: Alternative to fiberglass if you can stomach the extra cost, but there is growing evidence of possible health concerns. Rock wool is a more effective insulator than fiberglass, and it does a better job dealing with moisture. This would be a good choice for insulating door panels, but foam board is still a better (and cheaper) choice for the rest of your van. Rock wool also has some emerging health concerns, so if you use this make sure to wear protective gear and seal it off completely from the rest of your van.

Recycled Denim Batts

denim van insulation by @thevanprogram

Photo by @thevanprogram
  • R-Value Per Inch: R-3.7
  • Cost for 1 ft2 of R-1: $0.31
  • Where to Buy: Most big box hardware stores

Denim batt insulation is made from recycled cotton blue jean material. It’s non-toxic and very environmentally friendly. Denim has the same R-value per inch as fiberglass, but it’s quite a bit more expensive (although it’s cheaper than rock wool).

One major drawback of denim when it comes to van builds is that it easily soaks up and holds onto moisture, so you definitely don’t want to get this stuff wet. It’s also more expensive than both fiberglass and sheep’s wool.

VERDICT: Better than fiberglass, but it’s too absorbent and mold-prone for general use in a van. Denim batts are much more pleasant to be around than fiberglass, and could be a good option to insulate cavernous areas like door panels. But because it’s so absorbent and relatively expensive, we don’t recommend insulating your entire van with it.

Sheep’s Wool Batts (Havelock Wool)

sheep wool van insulation by @diamondsdreamcatcher

Photo by @diamondsdreamcatcher
  • R-Value Per Inch: R-3.7
  • Cost for 1 ft2 of R-1: Varies; $0.14 on average
  • Where to Buy: Havelock Wool

Sheep’s wool is a renewable insulation material that’s non-toxic, very environmentally-friendly, and has some great benefits. It doesn’t have the highest R-value per inch – it’s about the same as fiberglass and rock wool – but its relatively low price, moisture management properties, and environmental friendliness make it an attractive option (one that we’re sold on using for van build #2).

One big benefit of sheep’s wool insulation is its breathability and moisture control properties. Sheep’s wool can absorb moisture in the air without compromising its insulation abilities, and it will wick condensation away from your van’s metal wall. It’s also naturally resistant to mold and mildew, has some sound deadening properties, and even helps purify your air.

Because of its lower R-value per inch you’ll need more thickness than you would with foam, which may take away from your van’s interior space. But because you don’t have to worry as much about the effects of condensation with sheep’s wool, it’s much more fool-proof to install.

The one downside to sheep’s wool is that it’s not as available in brick-and-mortar retailers, so you will have to order it online – which adds shipping costs to the equation. The good folks at Havelock Wool are working hard to reduce shipping costs for smaller “vanlifer” orders, and they are currently at about 20%-25% of the order total.

VERDICT: Great choice for van insulation, especially if environmental impact and health are top priorities. We really love a lot of things about sheep’s wool insulation. It’s 100% natural, it’s environmentally friendly, it’s resistant to mold and mildew, and it helps manage moisture and condensation.

If you’re concerned about VOC’s, air quality, and condensation inside your van – and if you prefer to use natural materials – then sheep’s wool is an excellent choice. We’re pretty much sold on using this for our next build.

However, sheep’s wool insulation has a lower R-value per inch than foam board, which means you’ll need to give up more interior space to get the same insulating effect. It’s also a bit more expensive, especially after factoring in shipping costs. But depending on your needs and priorities, these trade-offs may be worth it.

3M Thinsulate

3m thinsulate van insulation by @sprocket3

Photo by @sprocket3
  • R-Value Per Inch: R-3.2
  • Cost for 1 ft2 of R-1: $0.53
  • Where to Buy: Amazon

Thinsulate is a synthetic insulation material produced by 3M. Originally designed for use in clothing, Thinsulate has become increasingly popular in van builds of late.

Thinsulate is attractive because it combines decent insulation properties with sound deadening and moisture control. The synthetic fibers it’s composed of do not retain moisture, but they do allow it to pass through – meaning Thinsulate will not trap condensation behind it. It’s also non-toxic and easy to install – just glue it up with spray adhesive and you’re good to go.

But, Thinsulate has the lowest R-value per inch of any insulation material we look at here. You would need nearly twice the thickness to match the R-value of foam board insulation, which is a tough sell when every inch of interior space counts.

It’s also expensive – more than four times as costly as polyiso for the equivalent R-value, and much more expensive than sheep’s wool.

VERDICT: Great product and good for nooks and crannies, but there are cheaper choices for the rest of your van. There’s something to be said for Thinsulate’s moisture control properties, but in our opinion it’s just too expensive for general use in a van.

If you’re interested in Thinsulate because of its breathability and moisture management abilities, we highly recommend looking at sheep’s wool insulation instead. It’s much cheaper and has a higher R-value per inch.

Lizard Skin and Other “Insulating” Ceramic Paints

lizard skin van insulation by @sugasrt

Photo by @sugasrt
  • R-Value Per Inch: N/A
  • Cost for 1 ft2 of R-1: N/A
  • Where to Buy: or Amazon (ceramic additive)

We’ve seen some discussion about using insulating paint like Lizard Skin as an alternative to standard insulation in van builds. Lizard skin is essentially paint with ceramic micro bubbles suspended within it.

Basically, you spray this stuff on the interior (or exterior) of your van, and once it dries you have a very thin layer of ceramic that forms a super effective heat barrier – or so the manufacturers of these products claim. You can also buy just the ceramic microbubbles and add it to the paint of your choice.

While this sounds like a great idea in theory, there is no actual scientific research that backs any of this up. The EPA does not recommend using these products in place of bulk insulation, and there are even tales of quixotic homeowners insulating with only ceramic paint and having severe heating and cooling issues with their homes – not to mention pissing away thousands of dollars in the process.

Not only that – this stuff is expensive. Lizard Skin costs upwards of $180 for a 2-gallon bucket (you would likely need 8 gallons or more to insulate a van). Buying the ceramic additive and using it with your own paint is much cheaper, but there’s still no evidence that it does anything at all for temperature control (in fact, just the opposite).

VERDICT: There’s zero evidence this stuff works. While we really want this to be a thing, it’s just not (at least, not right now). Because of the high cost and dubious insulating value, you’re much better off spending your money on proven materials like foam board insulation or sheep’s wool. If you have a bunch of extra money and want to experiment, go for it, but we just don’t recommend this for most people.

However, if research came out that ceramic paint is indeed effective, we could see it being used in conjunction with standard insulation as an exterior coating to prevent the metal body of your van from absorbing heat in the first place.

Van Build Insulation: What We Recommend

In our opinion, the best all-around material for van insulation is sheep’s wool insulation. Sheep’s wool is a sustainable product that insulates well, naturally manages moisture and condensation, and even helps purify the air in your van. It also has sound dampening properties, reducing the need for a separate sound deadening product.

However, if you don’t have the time or budget to go with sheep’s wool, we recommend using polyiso foam board to insulate your camper van. Polyiso has the highest R-value per inch (R-6) of any common insulation, it’s non-toxic, easy to work with, and isn’t terribly expensive.

If you can’t find polyiso in your area, we recommend going with extruded polystyrene (XPS) foam board. XPS also has a high R-value (R-5 per inch) and is slightly cheaper than polyiso.

Here’s How We Recommend Insulating Your Van:

  • Walls: Use sheep’s wool -OR- polyiso foam board, glued to the van body using Great Stuff spray foam or 3M High Strength 90 spray adhesive. Fill any gaps with spray foam.
  • Ceiling: Use sheep’s wool -OR- polyiso foam board, glued to the ceiling using Great Stuff spray foam or 3M High Strength 90 spray adhesive. Fill any gaps with spray foam.
  • Floor: Use 1/2″ XPS foam board. Another option is Reflectix, which will provide at least some sort of thermal break without taking up too much height.
  • Windows: This is highly important. Use reversible window coverings with a radiant barrier on one side (like Reflectix, Insul-Shine, or EZ-Cool). Face the radiant barrier outwards on hot days to reflect heat away from the van. Face it inwards during cold weather to retain heat inside the van. For the windshield, use Reflectix or a purpose-built reflective windshield covering (Eclipse Sunshade makes badass retractable coverings that stay mounted to your windshield, which is what we have on our van).
  • Ventilation: We always recommend installing a vent fan. Combined with proper insulation, a vent fan can both keep your van cool and help you deal with moisture and condensation.

This insulation setup should work very well for most people in most climates. But if you regularly deal with extreme heat or extreme cold, there may be a few other things to think about (which we discuss below).

How much does it cost to insulate your van?

You should be able to fully insulate your van with sheep’s wool insulation for about $350 to $550 (including shipping), depending on the size of your van.

Using foam board, you should be able to fully insulate your van for about $150 to $250 (we spent about $150 to insulate our standard wheelbase Chevy Express).

Warning About Reflectix

Reflectix is a primarily a radiant barrier. It does a great job as a window covering, but as soon as you stick it behind your walls without an air gap it becomes effectively worthless as a radiant barrier and you only get the benefit of its low R-value.

We recommend using Reflectix to shield your windows or to line large cavities (such as inside door panels). But you’re better off with foam board for everything else.

Do You Need a Vapor Barrier?

vapor barrier van build by @creativefreedom713

Photo by @creativefreedom713

There’s a lot of debate about vapor barriers and moisture control in van builds. There are two sides to this debate:

Argument 1: You need a vapor barrier to prevent your van from rusting out. When you live in a van you create a lot of moisture from cooking, running a heater, and just breathing. When warm, moist air from the living space reaches the colder metal of the van walls, it condenses into water and gets trapped, potentially causing rust and other problems over time. To keep this from happening, you need to install a vapor barrier between the insulation and your living space, so that moisture can’t even get to the metal walls.

Argument 2: You don’t need a vapor barrier because permeability and proper ventilation will allow any moisture to escape. The idea here is that you’ll never be able to completely seal off your van’s walls from moisture. If you install a vapor barrier that’s not 100% sealed, then moisture will become trapped behind it, potentially causing rust and other issues. Therefore, you should skip the vapor barrier and make sure your van has good ventilation and drainage, so that any moisture will just evaporate back into the living space.

Our opinion: Don’t worry about putting up a separate vapor barrier. If you use foam board insulation (or spray foam) for your van build then you’ve effectively created a vapor barrier anyway, since foam is impermeable to moisture. However, if you go this route it is vitally important to properly install your foam board so that there is no possibility of moist air becoming trapped behind it. This means making sure it’s installed right up against your van body so there are no air pockets, and sealing any seams with spray foam and foil tape.

Another option is to use an insulation material that won’t trap condensation no matter how you install it. Breathable materials like sheep’s wool insulation, rock wool, and Thinsulate manage moisture and allow it to naturally evaporate out of your van. If you use this type of insulation, then no vapor barrier is needed.

In terms of moisture control, it’s extremely important to make sure your van has proper ventilation. A good vent fan like the MaxxFan Deluxe 5100K is your best friend when it comes to moisture control. Even in cold weather, it’s a good idea to run your fan every so often to pull out moisture.

It’s also worth mentioning that your van has drain paths built into the floor, so any condensation that does drip down the walls can flow out of the van.

Why You Need Proper Ventilation in Your Van

van insulation vent fan

A vent fan is pretty much a necessity for comfortable vandwelling, and we think every van should have one installed.

Vent fans help you with both moisture control and temperature control, and they also make sure your van stays safe while cooking or running a heater.

If you’re dealing with humidity or condensation, running your vent fan will help pull moist air out of your van. When it’s hot out, running your vent fan with an open window creates a nice breeze inside your van, removing hot air and pulling in cooler outside air.

We have a Fan-Tastic Vent installed on our van that works well, but we recommend going with a MaxxFan Deluxe due to its built-in rain cover and lower profile.

Don’t Forget the Windows!

van build insulated curtains

Your van’s windows are the biggest sources of both heat penetration in the summer and heat loss in the winter. If you spend a bunch of time and money insulating but don’t do anything with the windows, your van just won’t be nearly a comfortable as it could be.

At the bare minimum, we recommend installing curtains made out of insulating thermal fabric. Even better are reversible window coverings with a reflective surface on one side. You can easily make these out of radiant barriers like Reflectix, Insul-Shine, or EZ-Cool, paired with dark fabric.

On hot summer days, putting up your window coverings with the reflective side facing outwards will reflect radiant heat away from your van. On cold winter nights, facing the reflective side inwards will reflect radiant heat back inside.

Here’s the setup we have in our van: we made reversible curtains out of Insul-Shine insulated reflective batting on one side and dark blue fabric on the other. We use these curtains to cover the windows in the rear living space.

For the cab, we have a retractable Eclipse Sunshade mounted to the windshield and reflective coverings for the driver/passenger windows. We also have a thermal curtain that we can close to separate the cab from the living space, which helps us trap more heat when it’s really cold out.

Want an Eclipse Sunshade? We don’t blame you, because they’re awesome. Buy yours using this link to receive a 3% discount off your order.

What About Sound Deadening?

sound deadener by @justanothervanbuild

Photo by @justanothervanbuild

We didn’t put any sound deadener in our van but we wish we had because the road noise is pretty loud (although some of that is due to the old, leaky door seals). It’s too late for us to put sound deadener in the living space, but we plan on adding some to the cab in the future.

The insulation itself will provide some sound deadening, but adding a dedicated sound deadener like Noico’s sound deadening mat to your van’s bare metal before insulating will help keep road noise to a minimum.

Insulating for Different Climates

Many vandwellers find they can stay most comfortable by following the seasons. So, they move to cooler areas when it gets too hot, and warmer areas when it gets too cold. If that’s you, then the insulation system we recommend above should be just fine.

But what if you spend most of your time in areas that are extremely cold or extremely hot? Well, you may have to change things up a bit or put more focus into mitigating certain things.

Insulating for Extreme Cold: More R-Value and Less Thermal Bridging

winter van insulation

If you spend a lot of time in very, very cold weather, you will probably want to insulate thicker than 1” to get more R-value. You will also want to reduce thermal bridging as much as possible to prevent as much heat from escaping as you can.

To achieve this, we recommend starting with a layer of ¾” to 1” thick polyiso or XPS foam board** in between the ribs of your van. Then, install another layer of ½” to 1” foam board covering the ribs. This gives you between R-8 and R-12 depending on how thick you go, and the second layer of foam eliminates the thermal bridging from the van’s metal ribs

Alternatively, we recommend insulating with thicker sheep’s wool insulation between your van’s ribs, and adding a thin layer of another breathable material like Thinsulate to cover the ribs.

Insulating this thick will cost you some interior space, but if you typically find yourself in very cold weather then that may be a worthy tradeoff.

If you have windows in your van, adding insulated window coverings with a reflective surface facing inwards will greatly reduce heat loss through your windows, and the reflective surface will help keep radiant heat inside. We have reversible reflective curtains in our van, and they make it noticeably warmer inside when we face them inwards.

In extreme cold, you’ll also want some sort of active heat source like a Mr. Buddy heater. But insulating well is the first step to keeping heat inside your van.

**Note: While we generally think polyiso is the best overall choice for foam board insulation, if you’re regularly in extreme cold environments you may want to consider XPS instead. There has been some research that shows polyiso’s R-value decreasing in very cold temperatures, to the point where it’s less effective than XPS. The jury’s still out on this, but it’s something to think about.

Insulating For Extreme Heat: Active Ventilation and Reflective Window Coverings

summer van insulation

Is there ever a time you shouldn’t insulate your van – like if you spend all your time in really hot weather? There’s a bit of a debate on this question, and the answer really depends on your overall setup.

Some argue that if you only spend your time in hot climates (i.e. Florida or somewhere similar) then insulation may do more harm than good. The argument is that while the insulation will slow down the heat from getting into your van at first, once it does get in the insulation actually prevents it from radiating back out once the day cools off.

But, that’s only really an issue if you don’t have any sort of active ventilation.

Installing a good ventilation fan will really help you control the temperature in your van.

A vent fan creates nice air flow that helps keep you cool. It also sucks out hot inside air and pulls in cooler outside air, which basically takes the insulation out of the equation when it comes to heat escaping at night. When we’re in hot weather, we run our vent fan literally 24 hours a day and it works wonders.

Here’s our opinion: if you have a very bare bones setup (i.e. no electricity or vent fan) and only spend time in hot climates, then insulation may trap heat inside when you don’t want it to. But if you’re installing an electrical system and running a vent fan (so there’s an active way for heat to escape), then insulating will only help with temperature control.

This is actually one time you may want to consider using Reflectix with an air gap between your van’s metal walls and the Reflectix. That way you’ll have something reflecting radiant heat during the day, but not stopping heat from escaping at night. But, we do not recommend doing this if you plan on spending any time at all in colder weather.

No matter what kind of setup you have, we highly recommend installing reflective window coverings if you spend time in hot weather.

Your windows are the biggest sources of heat coming into your van in the form of radiant heat from the sun. Adding reflective coverings to your windows during the day will reflect radiant heat away from your van and keep the inside much cooler. For covering your windshield, we highly recommend the Eclipse Sunshade retractable windshield cover.

Insulating Your Van: Step-by-Step

insulating your van step by step

These instructions are for insulating your van with foam board. If you choose to use sheep’s wool insulation, you can find some helpful installation videos here.

We recommend using ¾” to 1” polyiso or XPS foam board to insulate your van, glued in place with either Great Stuff spray foam or 3M High Strength 90 spray adhesive. If you choose to insulate your floor, we recommend using ½” XPS due to its compressive strength.

We wrote a post with detailed information about how we insulated our van awhile back that we recommend checking out. But we’ve learned a bit since then, and here’s our updated step-by-step:

  1. Make templates out of cardboard. Cut to fit the areas in between the ribs of your van walls and ceiling. If you plan to insulate your floor, make templates for this too.

    Pro tip: Keep all your templates! You can reuse them later when you install your wall paneling and your flooring.

van insulation cardboard template
  1. Trace the templates onto the foam board with a Sharpie, and cut with a utility knife.
  2. Install each panel one-by-one. Spray Great Stuff on the back of the panel along the perimeter as well as a few lines across the middle. Make sure the perimeter is completely covered.
van insulation bracing by @landonjump

Photo by @landonjump

  1. Once the panel is coated in Great Stuff, press it against the van wall and brace it with a piece of lumber until the spray foam sets. If your van wall is curved, use several pieces of lumber to get the foam to conform to the curved surface (XPS is more bendable than polyiso if you have really curvy walls). Repeat these steps with each additional panel.
  2. Ceiling: Follow the same process, once again bracing each panel with lumber until the spray foam sets.
van insulation ceiling by @landonjump

Photo by landonjump

  1. After all your insulation panels are installed, fill any gaps with spray foam. Once the foam dries, cut off any excess with a utility knife.
  2. If you choose to insulate the floor: use cardboard templates to cut ½” XPS or Reflectix to fit. Spray the underside with 3M High Strength 90, set in place, and weight it down until dry.
van insulation floor
  1. Door panels: Use the same method to install foam board insulation. Or, use 3M High Strength 90 to glue up thicker batting insulation. Another option is to line the door panel with Reflectix, since there will be a natural air gap to help hold heat in.
  2. Wheel wells: Wrap the wheel wells in Reflectix, glued down with 3M High Strength 90. Tape the seams with foil tape or Gorilla tape.
  3. Vehicle frame: Fill the frame with Great Stuff spray foam, or stuff with loose fill or batt insulation.

And There You Have It! A Fully-Insulated Van!

fully insulated van build

Now you’re ready to head off to Alaska in December, or drive down to Baja in July.

Well, maybe not. No matter how well-insulated your van is, it’s still a good idea to follow the weather you want. While insulation does make the inside of your van more comfortable, vanlife isn’t about sitting in your van – it’s about getting out there and enjoying everything this world has to offer!

For more epic build guides, vanlife tips, and puppy photos, be sure to follow us on Instagram @gnomad_home and on Facebook. Cheers!

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JohnOliveLoucakenJohn Allen Recent comment authors
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Excellent!! Thank you for this very thorough report.


This is such an excellent article! Many thanks!!

Out of interest, if you were to go down the ‘Extreme Cold’ route with a layer of insulation over the top of the ribs, how would you recommend attaching battens/cupboards/walls since there won’t be any surface area left?

Brandon Hood
Brandon Hood

Thanks for sharing the info. I was wondering should I put the Noico down on the floor first then put Reflectix on top of it or vice verse?


Hi! After reading through this, I still can’t decide where you stand on batts to use for door panel insulation and frame insulation on the lower parts of the van walls below the windows. I intend on having these sections fairly, if not completely sealed off from the living area, because they’ll be under wood paneling and other insulation, but you listed how toxic some things can be and how they can hold onto moisture, so which is best, just for door paneling?



Hey there! Just wondering if you find that there is much squeaking with the foam board when you’re driving? And it is any good for sound deadening in general for the van? We’re at the insulation step of our van build and there’s so much research to do! All the info you guys are posting on this site is a great help! Thank you!


I plan to live in a van near Fairbanks AK so this article was extremely interesting. I can’t move too far because I will be attending college so the info about extreme cold was awesome!

Van Dweller
Van Dweller

While insulation can help with sound deadening, your money is better spent on good heating and cooling devices for temperature control. Shade, lots of windows for ventilation, fans, and the indirect type of swamp coolers is the only off grid viable solution to hot weather. Dry heat, lots of windows and sunshine are the best solution for the cold. Most kerosene heaters fall into this category and can also run diesel if kerosene isn’t readily available. It’s cheaper, safer, and drier than unvented propane heat, and my 23k BTU kerosene heater keeps me toasty even during Alaskan winters. If you… Read more »


Hi Van Dweller, I’m also down here in FL. Can you link the indirect swamp cooler you use? I can’t find any indirect coolers at 12v. Thank you very much and happy trails.


Great writeup! Here are a few things you missed: Polyiso loses 25% of its R-value when the material gets really cold. For instance, in the dead of winter when pushed up against an ice cold metal van skin. Putting something that doesn’t suffer from that as the very outer layer might make sense. The second thing you didn’t note is that XPS loses much of its R-value when it gets really hot, such as in the desert, pushed up against a searing hot van skin, so ditto on that one. Those are two things one wants to keep in mind,… Read more »


Thank you for the awesome informative article. So helpful!
But why did you choose to cover the wheel wells with reflectix? Why not with some sounds damping material and maybe a spray foam or something?

Thank you

Greg Wilson

Two questions:

1. Do you run electrical wiring after insulating? I am guessing you make use of the vans grame channels for long runs of wire. But running to the spots needed do you cut a gap for the wire to run through, then fill with foam after? Or is it better to run electrical first and insullate over?

2. Do you reglectix over the ribs to break the thermal barrier?

3. Once wiring is done, fill the channels and ribs with batting?


Dear John.

Thank you so much for this very helpful article! Love it! I am insulating my VW T5 and I am dealing with big empty spaces in the frame itself. Would you recommend some RockWool/or other stuff and close of the holes with aluminium tape? Or is this still going to attract moisture?

After reading your article I kind of lost the interest in aluminium bubble foil
Thank you

Iain M Russell
Iain M Russell

Excellent article. Many, many thanks. I was leaning towards denim with reflectix as a vapor barrier. My van is a 90’s cargo van with curved walls. The ribs are not like that of the newer style wher they can be filled. They would be more like an “l” beam. So the inside edges of the ribs are pretty much straight (vertical), the opposite edge follows the curve of the van wall top to bottom. So the space to be insulated varies from @ 2″ at floor, @ 4″ mid way up, to @ 1″ at the top. I would love… Read more »


Excellent presentation. My question on the the gluing of the polyiso would you get a better radiant barrier if you had an airspace between it and the backside (exterior skin)? Rather than gluing it directly to the wall. Other thing have you ever looked at Prodex?


Thanks, great article. What do you think about hemp?

Nikki St Laurent
Nikki St Laurent

Hey just wanted to post a side note to the great stuff spray foam… make sure it’s a nice warm day and it sets up so that you don’t have it seeping from the walls later after it warms up. Read that on another blog…sorry lol my mind is slipping lol as my kids like to remind me of how I’m getting old (42) lol Will be getting a van and heading out when I retire, boys don’t wanna “live” in a van?! MOM REALLY?! Lol Great blog and the info is just laid out very well with descriptive details… Read more »


what are some examples of how you could “do it wrong” for using the closed foam spray?

Cara Barnes
Cara Barnes

Very helpful!!!! An excellent article with some great advice and tips that i will definitely be following! I can’t thank you enough for all this helpful information. but…

I am slightly confused about what R-value is, I have searched it up and still don’t really understand 🙁 could you please explain?


Hi, I have a 1978 Chevy G20 with rather curvy walls and live in a very humid area. I’ve looked at most of the rigid foam boards, but once you go over half an inch in thickness, they’re not very flexible and I doubt they’ll conform to the curve of the wall. I was thinking of using 2 1/2″ thick rock wool against the outside with 1/2″ foam board on the interior side and maybe a vapor barrier in between. The manufactures (Owens-Corning, Thermafiber Ultrabatt) claim it’s mold, mildew, and moisture resistant. But you say otherwise, so I’m a bit… Read more »


HELLO i need someone who can do for me insulting my van . I live in louisoky. email me


I need someone to do for me. Please contact me if you do


Awesome comparison!! Truly above and beyond anything I’ve seen (and I’ve looked)!

Did you also look at the acoustic insulation properties of the various materials? Foam board is for sure my choice for temperature (R-value) but I’m trying to balance that against sound transfer. Any thoughts?


Unfortunately, all rigid closed cell foam materials like polyiso are very poor at sound dampening.
It is very important if you convert from a cargo van like sprinter or transit. Cargo vans are practically just metal boxes.
I’d personally choose vibration dampening mats + thinsulate for a cargo van conversion, not polyiso.


I work at Eco-Building Products where I represent several product lines, including natural insulation, and we have more sheep wool customers every year who are using it for van, bus, and RV conversions. Recently I have acquired a truckload of no-itch foil-faced R4 Applegate Cotton Duct Wrap (10″ by 15 ft) and Pipe Wrap (3″ by 25 ft) which I am selling at about 50% to 75% off retail, and I am thinking it would work for the floors, perhaps other areas too. One would probably use reflective foil tape to tape the seams between adjacent rolls of foil-faced duct… Read more »


Hi there, Really informative article! I recently saw someone put spray foam into the channels on the floor of the van and then level it off when dry so the floor is then flat and I suppose half insulated in terms of area. I don’t know what they did after but that seems like a good idea to start with? I am 6ft4 and desperately seeking the best way to insulate the bottom and top of the fan without taking too much space. It seems like if I use reflectix on the floor with a 1inch gap I my as… Read more »


Have you ever thought about using a Fibre glass semi rigid board? Most commonly used for commercial HVAC insulation, it is great for sound, tolerates vibration and has a high R value. There is a local master upfiiter near my home that uses JM spin glass 800, since everything they use is approved by MB it seems like a good choice. Would be nice to know your thoughts.


Thanks for all of the information! I’m working on insulated window covers for the cold. I’m curious, does the reflective side need to be exposed for the benefit – or if it’s covered with fabric, will it still work similarly?


An excellent overview of everything (all in one place for a change) that one needs to consider when insulating a van. I knew I’d like the blog when I scanned through it and saw your diagrams explaining the types of heat transfer, the importance of catering for condensation and the discussion surrounding vapour barriers. Then I got confused as to your chosen solution. I’m still struggling myself to find the best solution for insulating my van, so I’m not criticising you, I just thought your discussion was going to lead to a different conclusion than what most people seem to… Read more »


Hi! I’m about to convert my Metris, and your website it SO helpful!
One question – if I apply Noico sound deadening to the van walls, is it ok to then spray the adhesive directly onto the deadening material when I’m installing the polyiso foam boards?


Thank you so much for all of this! Can I ask how many cans of the 3M high strength 90 you ended up using?


What an amazing guide and information… thank you so much.


Good article – I insulated with two layers of xps and then covered with rubberized shower wall. bonding is a real challenge. Contact cements melts xps. Best glue I found was Gorrilla glue in the bottle to bond rubberized shower wall to xps. Note- the thermal expansion of the shower wall is substantial where as the xps is nominal. The Gorrilla holds it across all temperatures/expansion.

sophia james

Insulating your vehicle is less exciting of a process, but worth the energy in your build. Quality insulation is paramount for the unit’s lifespan. Leaking roofs could damage the property and cause damage to the insulation and the walls. If you choose the best coatings for your RV roof repair, you could save money in the long run.

Andrew Hiddalbrans
Andrew Hiddalbrans

Your incorrect with the issue of mood and rock wool. Water is not absorbed by the product and I’ve never found told on the insulation even where told is present on the covering material.

Greg Rose
Greg Rose

Great stuff. Inspiring, one hopes. Thanks


Great write-up, but there is some language that bugs me related to the R-value as defined in the article. I understand what you’re going for here and that most people aren’t familiar with terms like “thermal conductivity”, but its important to understand as there is a little misguided information in this otherwise well-written article. 1) R-Value is ALWAYS a number used to communicate an insulates ability to resist heat at a CERTAIN THICKNESS. R-value should not be the primary focus, as it’s more important to understand the relationship between R-value and thermal conductivity. Primarily because most insulates come in varying… Read more »

Deb sarosy
Deb sarosy

Does the polyiso foil side face toward the van or toward the inside cargo area? Also did you just use foam around it or some other spay/ caulk adhesive as well?


What’s your opinion on putting a layer of sheep’s wool batting under the plywood floor? I don’t see it mentioned anywhere as a good option. Thanks!


Cracking guide! I’m planning to insulate my van with sheeps wool, found rolls online containing a blend of 75% sheep wool, 15% recycled polyester, and 10% polyester binder 🙂 and wondering if you would recommend adding anything else underneath or ontop, other than the plylining?


Hi there, I’ve got some celotex, polyiso foam board that is off cuts from a builder friend that I want to use, it only has the silver foil on one side. Shall I use it with the foil side against the van metal wall or foil in the inside facing the ply? Thanks, Zach.


Hey guys, great informative site! I just bought a transit connect and about to start the build. The van will be primarily based in Southern California and most likely road trips during the summer months in warmer west side states. Insulating is racking my brain on the best route to go if at all? Do you recommend primarily XPS foam board for my situation? Thanks for the help!

John Allen
John Allen

Very helpful! All the info I needed 🙂

Misty Johnson
Misty Johnson

Thank you SO much for this guide! I’m just getting started on my Promaster and whoa it’s overwhelming. This was incredibly helpful. I bought my Maxx fan and Noico through your links 😉


i just duct taped my insulation between the van ribs instead of gluing it. will this cause mold?


Hi John, great article. Thank you for doing this. I’d like to know about your take on this. I’m in Yellowknife NWT Canada (quite cold in winter). Although after your article the hard foam like Polyiso and xps sounds the best solutions for my location and budget(although here everything is 5 times the price anyways…: I previously found quite a bunch of those high impact flooring puzzle mat -for free-. They are about 1/2 ” thick and I have enough to cover most of the areas in need and even double it in some if needed. To your opinion could… Read more »


Hi there– wondering how to properly insulate the ceiling (and therefore the entire van) with the presence of a ceiling fan. Do I make sure it can be covered with an insulated section? Have found your blog so helpful, thanks for making all this information available!

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