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!

Best Van Insulation
Havelock Sheep's Wool Insulation

Eco-friendly and all-natural insulation batts made from sustainable sheep's wool. Sound dampening, breathable, controls moisture, sequesters carbon, and easy to install.

Our #1 pick for campervan insulation.

Learn More
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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. 

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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.

thermal-bridge

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 and your health.
  • 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 Havelock 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***
1ReflectixR-4.4$0.39Windows, Cavities
2R-6.0$0.12Walls, Ceiling
3R-5.0$0.12Walls, Ceiling, Floor
4R-3.9$0.10Not Recommended
5R-7.0$0.27Gaps & Fill-In, Adhesive
6R-3.7$0.03Not Recommended
7R-4.3$0.64Door Panels
8R-3.7$0.31Door Panels
9R-3.7$0.14Walls, Ceiling, Doors
10R-3.2$0.53Nooks & Crannies
11Lizard 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.

Havelock Wool Sheep’s Wool Insulation

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 have been working hard to reduce shipping costs for smaller “vanlifer” orders, and they are currently down to about 15% 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 Havelock 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, Havelock Wool 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.

Since Havelock Wool is effective, environmentally-friendly, non-toxic, and helps mitigate moisture and sound in your van, we think this is one of the best all-around choices for van insulation.

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: Sprayfoamkit.com 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.

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: Lizardskin.com 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.

Best Van Insulation
Havelock Sheep's Wool Insulation

Eco-friendly and all-natural insulation batts made from sustainable sheep's wool. Sound dampening, breathable, controls moisture, sequesters carbon, and easy to install.

Our #1 pick for campervan insulation.

Learn More
We earn a commission if you click this link and make a purchase at no additional cost to you.

If you don’t have the time or budget to go with sheep’s wool, we recommend using polyiso foam board or XPS 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. While polyiso offers the highest R-value per inch of any foam board, its performance does degrade in cold weather. So if you’re planning on camping in winter conditions, XPS may be the better choice.

XPS also has a high R-value (R-5 per inch) and is slightly cheaper than polyiso. It also maintaines its effectiveness in cold temperatures, so it’s a better choice if you’re using your van to, say, travel around to different ski slopes in the middle of winter.

Here’s How We Recommend Insulating Your Van:

  • Walls: Use Havelock Wool -OR- polyiso/XPS 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 Havelock Wool -OR- polyiso/XPS 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 Havelock Wool sheep’s wool insulation for about $300 to $600 (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 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.

Best Vent Fan
MaxxFan Deluxe 7000K

Powerful 10-speed roof vent fan with thermostat, remote control, and built in rain cover. Easily the best fan option for full-time vanlife.

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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.

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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.

Best Vanlife Sound Deadener
Noico 80 mil Automotive Sound Deadener

Why overpay for sound dampening? Noico deadens the vibrations on your van's metals panels, drastically cutting road noise and exterior sounds. All for a fraction of the cost of other brands.

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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 Havelock 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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  • Hi,
    Quite a nice write up.

    I did some testing on various types of insulation for moisture management and insulating value in a realistic van setup. Results here:
    https://www.buildagreenrv.com/insulation-testing-for-van-conversions/

    One thing you don’t mention that I think is valuable to know for van insulation is that both XPS and EPS have a max service temperature of 165F, and under hot sunny conditions (particularly for non-white vans) the sheet metal can reach these temps.

    Gary

    • Hi Gary, thanks for the comment. I refer to your website in a few places on our site, it’s packed with great info. We’re working on an update to this post and will be sure to mention temperature considerations for different materials. Thanks again!

      ~John

  • Thanks John, Great information. I have replied to a comment further down in the thread with regards to a discussion about cork insulation. But, wondered if you’d had anymore exposure to cork builds in the last couple of years? I am UK based and although not the cheapest insulation, cork is widely available here (I remember using self-adhesive cork tiles in my first VW conversion 20 years ago!). I’m using cork boards for under-floor & ceiling and granulated cork for in-filling the cavities in walls and door panels. It’s pretty light weight and as I understand, it should be very good for handling moisture and be resistant to mold problems. Hoping that it’s also the most sustainable and environmentally-friendly insulation available.

    • Hi Richie, glad the post was informative. We have since seen some builds that used cork insulation in interesting ways, and it’s definitely one of the options we are considering for our next van. We’re gearing up for a major update of this post that will go into further detail on cork, as well as examine the environmental aspects of all the materials. Hope that helps!

      ~John

    • Hi C, the R-value we list is per inch of thickness. While the total R-value of Thinsulate is 5.2, this is for 1.75″ thick material. Our goal here is to compare different insulation materials on a 1-to-1 basis that the layperson can understand, so we calculated R-value per inch for all materials rather than go with something like total R-value or K-value. Hope that clarifies!

  • I am on the fence about whether to use the lambs wool or Rockwool insulation. The Rockwool is much cheaper around here and there’s the savings on not paying for shipping to consider, but that lambs wool looks pretty nice. Whichever I go with, can the batts go directly against the inside of the metal wall?
    And thank you for all the useful info!

    • Hi Fred, both can go against the metal wall. They are both breathable and naturally derived. The lamb’s wool is awesome, but it may not justify the cost if there’s a big difference. Hope that helps!

  • Hi again…found the answer to my question…metric (SI) vs. inch-pound (I-P). Need to multiply by 5.678263337. Something to watch out for if you are from Europe, Australia etc and using American based data.

  • Hi John
    Can you expand on where you obtained the R-Values per inch from in your table. The Rockwool for example has a thermal conductivity of 0.044W/mK (www.rockwool.com). The R-Value is related to the thickness of the material so 1″/25.4mm of Rockwool only has an R-Value of 0.58. To achieve the R-Value of 4.3 in your table wouldn’t you need a thickness of 7.4″/189mm?.

    • Hi John, I obtained these values of using a fairly simplistic method of looking at insulation R-values and dividing by the material thickness. To use Rockwool as an example, an R-15 batt of Roxul Comfortbatt brand rock wool (view at Lowes.com) has a thickness of 3.5″. R-15 / 3.5″ = 4.29. I realize this is an imperfect way to calculate this, since thickness does play a role. To use another Rockwool example, the same brand batt in R-23 (view at Lowes.com)is 5.5″ thick, which equals 4.18 R per inch. R-23 / 5.5″ = 4.18.

      Hope that clarifies things!

      ~John

  • To the editor or those in the know,

    I am finalizing my insulation plan for my 1987 Vanagoin Syncro. I have already applied sound deadener to all paneling. I thought that applying the silver foil might be good againt the sound deadaner then wool but it seems that after reading your digest on silver foil requiring an air gap to work effectively I am convinced of not and saving money therefore it sounds like I will apply the wool to all air cavities. I was wondering how you treat an area like the front end therefore the area between the front and dash. There are wires and ventilation here and of course the woirkings of the wiper mechanism. I suspect that if I placed the wool in areas around the vent pipes other than the moving wiper ars than this would be good as the front leaks a substantial amount of cold. As well loosely around the wiper mechanism should not hurt anything but I suspect that some amount of wool will find its natural resting spot in those areas. Your thoughts?

    I would greatly appreciate it. Does the wool come from you? I will be placing an oreder shortly.

    Thank you and look forward to your response.

    James Zeff
    [email protected]

    • Hi James, you are correct about the foil insulation – it needs an air gap to work effectively, so if you have the space to spare you are generally better off using an insulation with a higher R-value. As far as the front end goes, I would be very careful about insulating up there since as you saw there is a good chance of interfering with moving parts. Generally, you would just insulate the living quarters in the back, and perhaps use an insulating curtain in between the cab and the rear if you need to contain heat a bit more. Hope that helps!

      The wool insulation comes from Havelock Wool, which is an awesome company out of California. You can check them out here.

      ~John

  • Really good article, thanks! My main worry is sweating and condensation. I may have missed it, but what’s the best insulation or way to avoid moisture and mold once it’s closed in? I intend to get a black van too too, to avoid the white commercial look.

    • Hi Jay, the number one thing you can do to avoid moisture and condensation issues is to have good ventilation in the form of rooftop vent fans. A good fan and a cracked window will keep the air flowing and will help prevent condensation from collecting anywhere. We run our fan 24/7, even in cold weather, just so we keep the air moving (if it’s really cold we’ll close the window and run the fan on “ceiling fan mode” with the vent closed).

      As far as insulation goes, there are two general ways to insulate a van. The first involves using an impermeable insulation like rigid foam board (XPS, polyiso, etc). Foam insulation is cheap, easily available at big box hardware stores, and insulates well. It is also impermeable to moisture, which can prevent condensation from getting back to the metal walls in your van. However, if it’s not installed correctly, then moisture could potentially find its way behind the insulation and get trapped. Spray foam also falls under this category, but it is much more expensive and difficult to install vs foam board.

      The other general way to insulate a van is to use a breathable insulation material such as Havelock Wool or Thinsulate. These insulation materials tend to be a bit more expensive and harder to find (you can’t get them at Lowe’s or Home Depot, but you can easily order them online). These materials are fully breathable, so they will allow condensation to pass through, but also evaporate back out with good ventilation, and you won’t run into potential issues with moisture becoming trapped. This is generally our preferred method, but foam board works well also if you’re mindful about sealing everything off.

      Neither foam nor wool/Thinsulate should give you problems with mold.

      Hope that helps!

      ~John

  • We are looking to insulate a Ford E-series Shuttle Bus. Both sides are lined with windows. We want to cover most of the windows, insulating over them. What is the best way to do this without risking condensation & other problems?

    • Hi Abi, you can use the same method you’re using to insulate the rest of your bus to cover over the windows. In general, there are two main ways to go about this. The first involves using an impermeable insulation like rigid foam board (XPS, polyiso, etc). Foam insulation is cheap, easily available at big box hardware stores, and insulates well. It is also impermeable to moisture, which can prevent condensation from getting back to the metal walls in your van. However, if it’s not installed correctly, then moisture could potentially find its way behind the insulation and get trapped. Spray foam also falls under this category, but it is much more expensive and difficult to install vs foam board.

      The other general way is to use a breathable insulation material such as Havelock Wool or Thinsulate. These insulation materials tend to be a bit more expensive and harder to find (you can’t get them at Lowe’s or Home Depot, but you can easily order them online). These materials are fully breathable, so they will allow condensation to pass through, but also evaporate back out with good ventilation, and you won’t run into potential issues with moisture becoming trapped. This is generally our preferred method, but foam board works well also if you’re mindful about sealing everything off.

      Hope that helps!

      ~John

  • Thanks for a thorough supply of info, soon starting on our van! I’ve read a fair amount about thermal bridges but never seen any advice about how to insulate the van ribs? Obviously need to be able to see where to fix structures, but every photo I’ve seen in every blog shows bare metal ribs, major thermal bridges. What’s your take on this?

    • Hi Nick, great question. Most people tend to pack the inside of the ribs with insulation – either spray foam or stuffing some sort of loose fill insulation in there. We did a half-assed job of spraying foam in ours. This probably helps a bit, but obviously does not fully eliminate the thermal bridge.

      At the end of the day, it’s impossible to eliminate all thermal bridging in a van. Even if you were to cover the van ribs with insulation, you will still have fasteners attaching your walls/furniture to the van frame that will act as thermal bridges (albeit small ones). Still, we can mitigate them by using thermal breaks. You don’t necessarily have to “fully insulate” the exterior of the ribs to do this, but rather introduce a less conductive material that breaks the conduction of heat (we later wrapped some of our ribs in a thin, flexible foam material to help with this).

      Of course, some insulation is better than no insulation, so even without adding thermal breaks, insulation is still adding to the general comfort of your van. Going all out with thermal breaks will help out a lot in more extreme temperatures – sweltering summer heat or freezing winter temps – but if you tend to avoid the extremes and stick to more comfortable weather, then you could get away more basic insulation.

      I’m personally a fan of insulating as well as possible, but I’m not certain of the best technique for eliminating thermal breaks in a van at this time. Hope that helps!

      ~John

  • As others have said, this is a fantastic write up! I’m wondering your thoughts on demin insulation. I understand it’s hydrophilic nature isn’t great, but since the stuff you buy at big hardware stores is all treated with boric acid to resist mold and mildew, do you think that would still cause issues over time?

    • Hi Eric, thanks for the comment! I would be very skeptical of using denim insulation in a van build. Even though it’s treated to resist mold and mildew, the denim itself holds on to moisture much more than a hydrophobic insulation like sheep’s wool or Thinsulate. And because a van is such a small space, moist air and condensation can quickly get into things, where in a house there’s more space for it to dissipate. Despite the boric acid treatment, mold would still be a risk, and if you have wood or other organic materials right up on the denim, these could mold as well.

      On the other hand, denim is very eco-friendly, available, and affordable, and works well. But if you do choose to use it, I think you would want to put up a vapor barrier between the denim and the living space, to prevent moist air from getting to it. Reflectix is a great material to use as a vapor barrier.

      Hope that helps!

  • Thank a lot for sharing this! It’s really helpful and thorough. I just wanted to ask if you need a vapour barrier at all if you use Sheep wool insulation. I was thinking of putting vapour barrier between the wool and the timber cladding.

    • Hi Michael, you do not need a vapor barrier with wool insulation. Wool is very breathable and also hydrophobic, so any condensation can easily evaporate out with proper ventilation. Hope that helps!

      ~John

  • This is an excellent article. Thank you . We have a question about sticking the polyiso foam board to the van…I have a 250 Transit van that we are converting. The upper portion of the walls curve and the foam board will likely leave air pockets between it and the walls. If we put great stuff around the perimeter of the back of the foam board and a few lines of it in the middle are we not creating a moisture trap?

    • Hi Gail and Jim, that is definitely the trick with properly installing an impermeable insulation material like foam board. As long as everything is sealed off and there is no way for moist air to get back there, then it shouldn’t become a moisture. Issues arise if the area isn’t completely sealed and moisture manages to get back there. Putting Great Stuff back there can fill the gap, and you can reinforce all of this by putting a layer of reflectix over your insulation as a vapor barrier, which will prevent moist air from getting into your insulation. Hope that helps!

  • Hi John

    What do I use to block out the window behind a shower wall in a Ford Transit van?I want to be sure it stays in place permanently since I wont be able to get to it ever again..
    Thanks Rosanne

  • Awesome write-up, thanks for the effort. I just researched the Owens-Corning XPS rigid foam, and they have indeed eliminated HFCs from their construction. I really wanted to make sure that was the case, and it is noted in the updated MSDS dated 6 June 2020. Cheers!

    • Hi Aaron, thanks for adding that info. We’ll be sure to note that when we update this article next. Cheers!

      ~John

  • Hi, Great read and very informative, I was just wondering what information you have to say that wool is an environmentally friendly choice?

    • Hi Doug, wool is a renewable resource that is not made from fossil fuels. Many of the options (such as foam boards and spray foam) on this list are made from petroleum products, and release harmful chemicals into the atmosphere during their production. Hope that helps!

      ~John

    • That’s what got me, too. Yeah, it’s renewable and not made from fossil fuels, but it still creates a good amount of CO2e. Animal agriculture in general is horrid for the environment, and sheep are no exception to that. See, for instance, Poore & Nemecek (2018), the recent IPCC report, and UN FAO reports like “Livestock’s long shadow.” Animal products, including wool, aren’t “eco.”

      • Noted and agreed. With building materials in general, eco-friendliness is often relative. When compared to something like XPS, polyiso, or spray foam, wool has the advantage of being renewable, biodegradable, nontoxic, and a natural product. Sheep’s wool also sequesters carbon (which makes up 50% of wool), in contrast with fossil-fuel-derived insulation, which actually desequesters stored carbon. This all serves to make wool’s payback time in emissions saved vs emissions expended much shorter than synthetic/fossil-fuel-derived insulations, and even cellulose-based products. But as you mention there are certainly emissions associated with animal agriculture. Another natural insulation material to investigate is cork. We haven’t looked into it too in-depthly as of yet, but it very well may address some of your concerns with wool.

        ~John

  • Great article but the webpage is over-monetised so the advertising distracts and detracts from the flow of the article.

    • Hi Freeman, thanks for the feedback. While we do monetize in order to keep our content free, usability is our primary concern. We’ll definitely take this into advisement.

  • Wow wow wow – that’s all I can say! Thank for sharing!
    QQ: how much space allowance should I make on the width? The van I’m looking at is 1787 mm and I am exactly 1701 mm, giving me 88.5 mm to play with on the width (I want to sleep side-to-side in the back of the Sprinter). This is about 3.2 inches … which doesn’t seem like a lot (enough?) to account for the insulation + whatever wall cover I/the builder chooses.
    Thoughts? Guidance? Am I cray-cray?? 🙂

    • So glad you found this helpful! Are those measurements between the frame ribs, or does that go all the way out to the sheet metal walls? Most of the insulation will be flush with the ribs – so if the measurements are rib to rib then you’ll still have inches to play with. Wall paneling goes on top of the ribs, and shouldn’t take more than 1 to 1.5 inches. If you are gungho on sleeping side to side instead of back to front, one strategy that some use is to sleep at a diagonal. Hope that helps!

      ~John

  • Hey! thanks so much for all your write ups! I’m in the process of building my Chevy Express with a fiberglass high top and your site has been super helpful (everyone else posts about Sprinters, Promasters, and Transits).

    One issue I have is that I hope to use the van to chase snow, and the Express ribs are pretty awkward to work with. I read you guys left the metal exposed for a while but have since covered it up. What are you guys using as a thermal break for the exposed ribs by the door and along the top (below the high top)?

    • Hi Aiguo, so glad you found this helpful! We think Chevy’s can be a pretty awesome base for van conversions. As far as thermal breaks, we wrapped the ribs below the high top with a flexible foam. Not a super high R-value, but at least it’s some kind of thermal break. The rib by the door houses a lot of our electrical wiring as well as our light dimmer and inverter switch, so we just faced it with a plywood panel. Hope that helps!

      ~John

  • Thank you so much for this site! We are “baby” VW Type 2 owners at the beginning of our rebuild. I read through your insulation page but didn’t see anything specific to sound dampening recommendations. Did I miss it?

    • Hi Kimli, so glad you enjoy the site! We have two general recommendations for sound deadening: there’s a product called Noico that you can purchase online that works equally as well as more expensive name brand options. Another option that some use is a product called “Peal ‘n” Seal,” which is a product you can grab from the roofing aisle at Lowe’s (Home Depot has a similar product under a different brand name). This is similar material to sound deadeners, and it’s what we used when we redid our floor. You can check out our post about that here: https://gnomadhome.com/vanlife-mold-prevention-flooring-redo/

      Hope that helps!

      ~John

  • Hi there!! Amazing article! Thanks for that! One question, please – I understand the difference between using sheep wool and spray foam, but … Is the higher R for spray form worth the risk of not installing it properly over the lower R factor for sheep wool, but that being riskless?

    • Hi Radek, it really depends on your needs and priorities. If your number one priority is R-value, then spray foam is tough to beat. But, there are some additional complexities/costs to installing spray foam. Sheep’s wool is easier to install, is more environmentally friendly, and is nontoxic, but it definitely is not as efficient in terms of pure R-value. There are good use cases for both, but it depends on what you value more. I hope that helps!

      ~John

  • more please on reflectix for window coverings. i’m reading some suggesting it can get so hot to ‘break windows’. i have reflectix coverings for my van’s windshield and have not had a problem, but i don’t keep it in place in the hot sun for very long.

    what are you finding on this question?

    • Hi there, I have not heard of Reflectix breaking windows. It’s very commonly used in budget van builds, and I’m not aware of any issues. Hope that helps!

  • Hello! I’ve been going back and forth about insulating my Ford Transit Connect Cargo van. My question is: if I insulate only certain areas of the walls (like in cavities), is that ineffective? And therefore not worth insulating at all? Will the areas not covered by insulation (like where the wheels stick out) defeat the purpose of insulating at all? Thanks so much!!!

    • Hi Penina, great question! Insulation is definitely not an “all-or-nothing” proposition, so some insulation is better than none. That said, having gaps and/or large uninsulated areas will reduce the overall effectiveness of your insulation. I’m not sure where the specific cost/benefit line is, however.

      To help you figure out if it’s worth it to insulate, think about how you plan on using your van. Do you plan to travel in extremely cold temperatures? Van insulation tends to be more effective at holding heat in, and can be a real game-changer in cold environments. If you’re mostly traveling in “comfortable” temps, then you may be able to forego insulation altogether. If you will be in hotter weather, then the biggest bang for your buck is going to be proper ventilation i.e. a roof vent fan (highly recommended no matter what), reflective window coverings to keep radiant heat out, and shade (both seeking out shady spots, and creating your own shade via an awning and/or a tarp setup).

      I hope that helps!

      ~John

  • Thanks for your webpage! It is very helpful and informative for those of us who are about to embark on such a mission. I am an RN who is planning to do very short assignments. I am planning to convert either a use Sienna or Odyssey by striping it down (a la Forestry Forest van in youtube), live in it and come back home to South FL from time to time. I would spent parts of all 4 seasons up North and West as do a variety of outdoor activities such as hiking and skiing.
    I want to contribute by addings studies on how Polyiso is such a horrible insulation for very frigid conditions, going from an R rating (1-inch) of 6 at 75 degrees F to R2 at 15 F (a loss of 66%!). XPS goes from R5 at 75 F to R6 at 15 F. Not only that Polyiso sucks and gulps water many times more than XPS. Polyiso may be OK in the Southern and Western non-mountainous regions in the US since dry and not so cold would be better. The Corning Brand FOAMULAR XPS “is the only XPS that is GREENGUARD Gold certified.” and it contains at least 20% recycled material….Not bad for a major conglomerate brand!
    https://www.owenscorning.com/NetworkShare/EIS/10019949-FOAMULAR-XPS-vs-Polyiso-Tech-Bulletin.pdf

    THIS is apparently an independent testing….Look at the R values for ALL manufacturers and how they drop…..There is also a difference in the quality:
    https://www.buildingscience.com/documents/information-sheets/info-502-temperature-dependent-r-value#Foot11

    Another article, you need a subscription but you get the gist of it:
    https://www.greenbuildingadvisor.com/article/in-cold-climates-r-5-foam-beats-r-6#:~:text=Although%20extruded%20polystyrene%20(XPS)%20is,6%20polyiso%20in%20cold%20temperatures&text=In%20cold%20climates%2C%201%20inch,has%20a%20higher%20R%2Dvalue.

    This is a presentation where the addition of certain chemical would make Polyiso much better at milder low temps like 40 F (but no freezing). I believe it is still not good enough FOR MY PURPOSE.
    https://web.ornl.gov/sci/buildings/2016/docs/presentations/principles/principles-01/Principles01_Paper159_Letts.pdf

    • Hi Fre, thanks so much for the info! We’ve definitely read about the temperature performance differences between these two types of insulation. We are working on updating this post and plan on adding additional information, as well as “green” ratings for each insulation type. Thanks again!

      ~John

  • Question: if you want to install sound insulation, where does it go? Under the thermal insulation right next to the body of the van? Or over the thermal insulation on top of the metal struts?

    • Hi Robin, sound deadening materials should go directly next to the body of the van. They work by adding mass to the metal panels, which prevents them from vibrating and transmitting sound. Hope that helps!

      ~John

  • Hi! We juste bought a Chevy Express 1500 Explorer Conversion van 1998. Basically the same as yours. This is sooo helpful. Quick question: What did you do with the holes in the floor from the seats bolts. I can see the grass under me van. Did you cover them from the inside or the outside? Did you use Great stuff or some metal sheet? I’m wondering what to do with that before starting my insulation. Thanks! 🙂 You website is a goldmine for us.

    • Hi Jeanne, thanks for reaching out! We actually did not cover the holes in our van. However, if you were to cover them up I would recommend doing so with a fiberglass patch kit (available in most hardware stores).

      ~John

  • how did you get the reflextix to stay on your windows? I have the same chevy can and am having the hardest time having it stay.

    • Hi Kevin, we actually sewed curtains out of a product called Insul-Shine, which is a reflective batting material. We fastened grommets around the top, and we hang them above our windows using cup hooks. Our curtains are reversible, so we can reflect heat out in hot weather and keep it inside in cold weather. As far as keeping Reflectix up, many people use velcro, or cut it slightly oversize so they can wedge it in there. Hope that helps!

      ~John

  • Wow amazing! Thanks for investing your time in making this page. It reaaaaally helped. Thank you a lot!!!

  • Love your article, possibly the most informative van insulation article on the net.
    This one like all. seem to miss other alternative insulating products commonly used in industrial applications. I’m talking about the likes of ceramic wool, superwool, Kaowool blanket/board and other cryogenic, oven and furnace insulating linings. These industrial linings have super high R factors, some are paper thin and can potentially be used to insulate vans. Definitely worth looking at.

    eg; https://www.amazon.com/Lynn-Manufacturing-Superwool-Blanket-Ceramics/dp/B07SRGTZVC?ref_=ast_sto_dp

    Personally, I’d like to try Aerogel with a binder but the cost is way too much.

    Anyway, keep up the good work. Much appreciated

    Cheers

    • Hi Wilson, thanks for the kind words! We’ll definitely look further into more alternative insulation products for our next update to this post. When I briefly looked into them in the past, many industrial solutions seemed like there wasn’t a lot of data related to “residential” applications (thus making them tough to compare to other materials), the cost was prohibitive, and/or sourcing was difficult.

      But we’re always on the lookout for better ways to do things and we’ll do some more digging. We have a home base now, so we’re planning on getting a cheap van shell that we can use to run some actual tests on different materials/products in the future. Thanks again!

      ~John

  • I’m scouting for a van to convert. I’ve been researching both cargo and passenger vans. If I go down the passenger/conversion van route will I need to insulate it? How much insulation do they usually have already?

    • Hi Scott, thanks for reaching out! In truth, that all depends. Our van didn’t have much insulation behind the walls – it was basically a very thin layer of fiberglass-looking material. But other manufacturers/converters could be different.

      As far as whether you need to insulate, it depends on how much work/customization you want to do, and where you plan on traveling with the van. If you’re mostly staying in comfortable or warm weather, you don’t necessarily need to add insulation. In hot weather, proper ventilation (i.e. vent fan), shade, and reflective window coverings will get you a lot more bang for your buck. Where insulation really matters the most is in cold weather – a well-insulated van can make a huge difference between comfortable and freezing.

      If you just want to do a quick build out without gutting the entire van (and you’re planning on staying in fairly comfortable climates) then you can probably get away with keeping the van stock. But if you’re doing a fully custom buildout that involes gutting the van anyway (or you’re planning on spending time in very cold places), then I would definitely take the time to insulate.

      Hope that helps!

      ~John

  • This is an amazing resource you’ve created! Thank you so much! I do have a question on the noico. Should that be for just the flooring or the walls too? As well as should it go under or on top of the insulation?

    • Hi Madelyn, so glad you found our site helpful! Noico and other sound deadeners need to go directly against the vehicle surface (i.e. under the insulation). They work by deading the vibration of the van’s metal paneling. Putting it on both the floor and the walls would be the most beneficial. But keep in mind, you do not need to completely cover the metal surfaces – there can be sizable gaps between the Noico sheets and they will still kill the vibrations of the metal. Hope that helps!

      ~John

  • hey dude am from india the dream of mine is building an van like this do you guys have any group or any online platform to get some suggestions or communicate with

    • Hi Sachin, thanks for reaching out! Here are a few communities/resources we recommend:

      1. Project Vanlife Forum
      2. Vandwellers Reddit.
      3. Vanlife Facebook groups. There are a ton of them out there. Some are more friendly/helpful than others, but there’s always a lot of activity and ideas.
      4. Instagram and Youtube. In terms of general vanlife inspiration, these two platforms have it in spades.
      5. Hope that helps you get started! Best of luck!

        ~John

    • Hi Jamie, the metal frame in many vans is hollow, but has openings that allow you to stuff insulation inside. When we say “fill the frame” we mean stuffing the inside with insulation material. Hope that helps!

      ~John

  • Hi. I’m still having doubts about using foam boards as it’s highly suspect that you can install them flush with the curved interior metal sheet walls without any air gaps. No amount of glue and certainly no greatstuff can guarantee a complete seal, which raises the question of moisture buildup and subsequently mildew possibility. I see very little support here for sparing kits that can leave out all doubts. Thanks.

    • Hi Mehrdad, I completely agree. To help further combat moisture penetration, some builders use a layer of reflectix or plastic sheeting outside the foam boards as a vapor barrier. However, I personally believe that using a breathable, moisture permeable insulation (such as sheep’s wool, rock wool, cork, or Thinsulate), combined with proper ventilation and airflow, is a better choice, since moisture cannot get trapped – meaning rust and mold are much less likely to be issues. Foam boards are cheap and effective as insulation and can be good budget options, but they may open you up to other issues over time. However, the real impact of this is unknown since insulation in campervans has not been thoroughly studied as far as I’m aware. Hope that helps!

      ~John

  • Take a look at armaflex or K-flex with adhesive back in a roll. Not so expensive, but R value is big and it is really easy to instal

    • Hi there, the standard batts that Havelock sells are 2″ thick, which gets you R-7. The insulation in our van is R-5, and we’ve found that we can stay fairly comfortable down into the mid-low 30’s without kicking on our propane heater. We’ve camped out in much colder weather (down into low 20’s/upper teens), but we definitely need to bundle up and run the heater right up until bedtime when it’s that cold. For hot weather, reflective window coverings, good ventilation, and shade (both natural shade and your own shade from an awning) are much more important than the amount of insulation behind your walls. Hope that helps!

      ~John

  • I appreciate your recommendation to use the canned spray to fill all the gaps and cracks. My wife and I love the idea of traveling around the states in a van while working remotely for a few years. We may consider spray foam insulation when we convert a van on our own.

  • WAIT THERE’S A * FREE RECYCLE PRODUCT INSULATION MATERIAL THAT WASN’T DISCUSSED HERE*!:

    This was a great very well done article and these open comments can open up more ideas and improvements.

    I would like to share with you how I insulated my 96 ford window ext van for FREE. Now my van is just for short camping and road trips so the most R value is not my objective.
    I wasn’t even going to insulate but Free recycled changed my mind! I’m Very glad I did because some of my camping party is very sensitive to the heat and I am very sensitive to the cold. When I shut my van doors with the loose polyfill it now sounds more solid and quiet like a meat locker door.

    A super cheap greatly overlooked free insulation material for what you might use to stuff into cavities in a van is used loose poly fill-pillow filling or sheets of poly batting as well and that you can fairly easily get for free from people’s worn discarded sofa’s are often found next to apartment or thrift store dumpsters OR the Foam From the discarded Seat Cushions-New foam is Very expensive but this foam is FREE and should also sound deaden some!
    The cushions often have zippers or just cut the seat open.
    To cut foam to desired size and shapes, I use a hack saw taken out of it’s holder, holding the blade loose in hand and saw back and forth although it does not work as quick and precise as an electric meat knife, it works ok.
    I didn’t use any foam to insulate because the loose poly fill and poly batting is so easy to work with but I will be back to a used sofa to get some free foam to make some seats in my boat next year!
    Gosh don’t use fiberglass insulation that goes in house attics, I think the loose fibers would get into your lungs no matter what and maybe cause cancer many years later, run from it like the plague for your van!

    Also note that the filling in used sofa’s have been covered and protected by the outer fabric so it’s usually in pretty good shape.
    The poly fill comes in different colors just like the plastic bottles it’s made from.
    Because any soft pillow pads or pillow backs can be full of the stuff. Just cut open with a knife to find out and take what you want before the garbage company crushes the sofa.
    Of course you’d want to give it a quick close scan smell with your nose on it in case it has pet urine but really most apartments deter pets by either not allowing pets or they charge a lot to have them and pets rarely pee on furniture.
    Manufacturers make the poly basically from plastic bottles and it’s fluffy and no one is allergic to it, it’s in our pillows and it doesn’t make you itch and it doesn’t absorb water and although it isn’t as good of an insulation as foam, it does insulate by holding the air in it’s fiber fluff pockets.
    Of course you can buy it new in bag at hobby departments but it can be kind of expensive and why buy new when you can get for free and save the environment from more new plastic?! Plus it would take a good number of bags of this stuff.
    ALSO of course for the floor insulation, a free alternative is used carpet foam can be found in dumpsters behind carpet stores.
    Some might be in very good shape as some people replace carpet often and some rooms just aren’t walked in much.
    If someone asks you what you used to insulate your van, tell them you used the guts of old sofas!
    What could be cheaper and help save our planet and reduce our landfills and our polluting factories? Reuse is a main part of recycle so maybe we need to get over our mental blocks of reusing vers buying new!
    Thanks again!

    • Hi Jim, thanks so much for commenting and for sharing these tips! I love how this method not only gets your van insulated, but also saves all of this synthetic foam from going into a landfill, where it would just take up space for hundreds of years. We’re all in favor of thrifty, environmentally-friendly builds around here, and we appreciate what you did!

      ~John

      • Thank you for saying so John!

        It’s the loose polyfil that I used and some of the polyfil batting where loose wouldn’t work, I didn’t use any of the foam from the sofas because the loose fill is so easy to work with.
        I definitely will be obtaining free used sofa sear foam when I redo my boat seats that are extremely weathered and old.

        I am using just a little spray foam in a can along the roof line edge to give the van roof sheet metal more support from the inside of the wall tops that don’t quite touch because of about an inch gap at the wall top perimeter and also in some of the van hallow pillars which might give them more strength in case of a roll over accident as filling hallow metal structures with a ridged material gives more strength in that when one wall of the metal is being forced upon to bend, it transfers that force to the opposite side wall making 2 walls that must bend at the same time to collapse the structure.
        Take care

    • Hi Lisa, Thermacork can be an excellent insulation material and it has many benefits. We recently toured a van build that used cork insulation to great effect. The big downsides for cork at this time, though, are cost and availability. You can’t exactly walk into a hardware store and buy cork insulation, nor can you easily order it online, and the costs are prohibitively expensive for the vast majority of vanlifers. However, we may consider adding it to this comparison in the future.

      ~John

      • Hi John, Thanks for your response and your whole website. But yes, you can walk into a hardware store now and buy cork insulation! It is all over the web too. 1/2 inch underlayment for a Sprinter van costs about $125. 1/4 inch underlayment is $75. So this is not expensive. It is so superior to alternatives because it is extremely lightweight, waterproof, fireproof, mold proof and also easy to access, easy to use, and cheap. So just want to encourage others to take a look. And here is a chart comparing the R-values of insulation that includes cork… Cork is one of the better materials out there. Oh, and it is harvested by real people from trees that are not cut down. So cork is also one of the most sensible materials out there. https://www.houseneeds.com/learning-center/pex-tubing-radiant-floor-heating/flooring-r-value-different-materials

        • Hi Lisa, I know this is a little late, but hopefully you will still pick up this message! I’m based in the UK and going to use SecilVit cork for my sprinter conversion. Cork boards under the flooring and on the ceiling, granulated cork for in-filling the walls and door cavities. What has your lived experience been with the cork over the last couple of years? Did you use any granulated cork to fill up gaps? Did you use a vapour barrier? I’d prefer not to use a VB, but would like to hear your thoughts. I think cork is the most environmentally-friendly and sustainable insulating material available!

  • 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!

    • Hi Olive, so glad our blog has been helpful! If your ceiling fan is already installed, you can insulate around the fan opening. We installed our fan before insulating, and insulating around the fan was a matter of cutting the insulation to shape (we used polyiso foam board). As far as making sure there’s an insulated section to cover the fan — it’s definitely a nice idea if you’re going to be in extreme cold, but since ventilation is so important in a van I’m not sure how much use you would get out of it. You could just cut a square of foam board insulation and wedge it up there, or they actually sell insulated vent fan covers on Amazon. Practically speaking, though, we have our vent fan running basically 24/7, even in cold weather, to help with ventilation and removing condensation – so I’m not sure insulating the fan opening is strictly necessary. Hope that helps!

      ~John

  • 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 those be a good idea as a solution for insolation, including floor, walls and sealing or not? Downfalls? Positives? If yes what would you use to glue them? And finally could those mat release toxic emanations under hot days?

    • Hi Louca, thanks for commenting! It’s tough to give specifics without knowing the product you’re working with. I’m sure it would provide some insulation value, and would be especially good on the floor. As far as using it elsewhere, you would probably need to layer it in order to compete with the R-value of XPS or Polyiso. As far as gluing it, we’ve had good luck using Great Stuff spray foam cans as adhesive. Other products to try would be 3M High Strength 90 spray adhesive or Gorilla Construction adhesive. But without knowing exactly what those floor tiles are made of it, it’s tough to tell what would adhere to it. Off-gassing is also an unknown, and comes down to the specific product that you have. Those flooring mats could be a good sound deadener, though, so one option would be to use them on floor/walls/celing and layer XPS over it for increased insulation. If you’re going to be in extremely cold temperatures, XPS may work out better since polyiso does show reduced R-value in very cold temps. Hope that helps!

      ~John

    • Hi Ken, this won’t cause mold. But the concern here would be if there is an air gap behind the foam insulation that could potentially trap condensation, which could cause rust over time. Foam board insulation is basically impermeable to water, so to install it properly you really want to make sure it’s sealed against any air penetration so that moist air can’t find its way back there and get trapped. Hope that helps!

      ~John

  • 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 😉

    • Hi Misty, we are so glad that you found this guide helpful! Thanks for the support, and best of luck with your build!

      ~John

      • Indeed. Instead of replacing the sheep wool insulation I originally fitted I’m keeping it to help with moisture management. PIR and expanding foam goes everywhere else and I’ll skip the moisture barrier.

        Fingers crossed all goes to plan!

  • 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!

    • Hi Jaclyn, thanks for commenting! In general we recommend XPS or polyiso foam board as good all-purpose insulation. It’s fairly cheap, has a high R-value, and will help slow heat transfer into your van through the metal walls. In hot/sunny areas, reflective window coverings, proper ventilation (roof vent fan, etc), and shade are extremely important. If you’re somewhere without natural shade, you can create your own with an awning. You can also shade the other side of your vehicle by clipping a white or silver tarp to their rain gutter and staking the other side to the ground. If you insulate your walls, have good airflow (vent fan), and keep sun out/away from your vehicle (window coverings and shade) as much as possible, then you can keep your van at a livable temperature during the day, and the vent fan will pull in cool air at night. Hope that helps!

      ~John

      • Thank you for the information! My only thought or concern after thinking is that I don’t plan to live in the van full time currently. Just camping trips and long extended trips. So that said I don’t plan to put a vent fan in or have a wiring solar panel and battery system. Since I am doing the bare minimum I am still wondering if insulation will be the best solution? Thank you.

  • 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.

    • Hi Zach, I would personally face the foil side in towards the ply, and make sure to seal any gaps in the polyiso with canned spray foam and foil tape. As far as insulation goes, the function of foil facing is to serve as a radiant barrier to reflect radiant heat. However, you need an air gap of at least 3/4″ for the foil to have any effect – and since air gaps are typically a waste of much-needed space in van insulation the foil will basically be a non-factor as far as insulation. But, foil is very effective as a vapor barrier – and if you use an insulation scheme that includes a vapor barrier like this, you want to make sure that it’s sealed very well to prevent any condensation from sneaking past it and getting trapped – hence filling gaps with spray foam and covering over with foil tape. Hope that helps!

      ~John

  • 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 Rob, I personally would not add anything in addition to the sheep’s wool – definitely not a vapor barrier of any sort. the big advantage of sheep’s wool as insulation is that it’s very breathable – which means it will allow moisture and condensation to flow through it and evaporate out, rather than potentially getting trapped behind the walls. Just using the sheep’s wool will allow it to do its thing naturally. Hope that helps!

      ~John

  • 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!

    • Hi Eric, thanks for commenting! You could use sheep’s wool batting under the plywood floor, but because it’s not a rigid insulation you would need to build a frame to support the floor above it. Height is typically an area where space is at a premium in a van, and rigid foam insulation offers much more R-value for the space. If you built a frame and put 1″ of sheep’s wool batting under your floor, you’d be at R-3.7. But if you instead used 1/2″ XPS foam sheets, you wouldn’t have to build a frame, you’d save 1/2″, and you’d be at R-3. Just a few things to think about. Hope that helps!

      ~John

  • 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?

    • Hi Deb, we recommend installing the polyiso with the foil facing inwards towards the cargo area. When we did our van, we used 3M high strength 90 to stick the insulation to the van body, then filled the cracks with Great Stuff Gaps N Cracks canned spray foam. However, the Great Stuff also works really well as adhesive for the foam, and that’s what we would do today (in fact, we installed insulation in a buddy’s van using this method). Hope that helps!

      ~John

      • If you are using the foam as an adhesive did you coat the entire back or just do strips, stick it up then foam around it or did you foam the entire back then stick it up?

  • 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 thicknesses. Thermal conductivity is independent of thickness. You’ll see why you want to target the lowest thermal conductivity, not R value, below.

    2) Thermal Conductivity should replace the world “R-value” in a few places in this post.

    3) The equation is like so for, say, aerogel Spaceloft:

    Thermal conductivity = .0145 W/m-K (often shown as 14.5 mW/m-K)
    Single sheet thickness = .01m (10mm)
    RSI (metric unit of R value) = Total insulation thickness/Thermal conductivity

    RSI value for a single layer of 10mm Spaceloft is therefore, .6896

    To convert to R value, simply multiply x 5.678, and R-Value = 3.9

    That means two layers of spaceloft (20mm) would have an R-Value of 7.8 and so on…

    So it’s important to understand that R-value in and of itself is kind of worthless because you most often need to optimize your R value within a given dimensional constraint (overall insulate system thickness) because your van space is valuable. You want to find materials with the lowest thermal conductivity.

    • Hi Chance, thanks for the honest feedback! We’re working on revamping and improving this article, and part of that will be clarifying and improving the language/concepts that we present here.

      My intention with the first iteration of this article was to present these concepts in a way that most people could understand, and since many people are already familiar with R-value (and since R-value is a readily available metric for most materials), I thought it made most sense to focus on that as a way to compare materials rather than try to explain K-value.

      But ultimately I want this article (and our site as a whole) to equip people with the information they need to make the best decisions for their rigs – which means accuracy and clarity.

      Thanks again for reaching out!

      ~John

  • 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.

    • Hi Andrew, thanks for commenting. I fear we weren’t as clear as we would have been in the first iteration of this post. I’m in the process of updating it to be more comprehensive and helpful, and I appreciate the info and the input. Cheers!

      ~John

  • 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.

  • 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.

    • Hi Mike, thanks for the tip! We had good results using Gorilla Construction Adhesive on our XPS. It bonds in under a minute and holds very well. We’ve also used Great Stuff canned sprat foam as insulation adhesive.

      ~John

  • 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?

    • Hi Sujay, you can apply foam directly on top of sound deadener material and it will not affect the sound deadening properties. Best of luck with your build!

      ~John

      • W_O_W! I am in the planning stages of a cargo trailer conversion and have been researching for three months now. You have confirmed my thinking after sifting thru all the nonsense out there. Thank you for a great site and all the great information.

        Really hope that LizardSkin stuff turns out to be REAL. That would make the build sooooo easy……

        • Hi JD, glad the post was helpful! There’s definitely a lot of confusion out there on the internet, but we’re trying to do our part to cut through the confusion for other DIY builders. It would definitely be awesome if something like LizardSkin worked well, but in the absence of further testing the jury is still out. In the future, we hope to buy a cheap van shell and run tests on insulation materials and other things, so stay tuned!

          ~John

  • 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 be doing, which involves sticking wall boards directly onto the van’s metal skin!

    When you said in the blog you’d forget about a vapour barrier, I thought I had found in you someone like myself who was concerned about avoiding trapping water vapour in between the inner and outer wall, in particular avoiding the dreaded interstitial condensation within the insulation itself; that is, when any moisture that finds its way in to a structure condenses within the fabric of that structure.

    Given we are talking about a metal container on wheels as the outer skin, with various drain holes, awkward cavities and the likelihood it will twist and warp due to movement and temperature changes, I prefer to assume that we cannot guarantee that the ‘cavity’ formed between the van’s skin and the constructed inner wall surface will remain moisture free. It will certainly never be a vacuum, right!

    Even if we went down the route of spraying with closed-cell foam, which is becoming popular, there can be no guarantee that every nook and cranny behind the subsequent inner wall will be filled with the stuff, especially within the struts. This means when there is the inevitable temperature difference between the inner and outer walls that contain these pockets of air, it will eventually reach dew point at some combination of inner/outer temperatures and condense. If the chosen insulation is not hydrophobic (i.e. absorbs water like a wool insulation), then the insulation will get damp and cause rot. But even if the chosen insulation is hydrophobic (i.e. repels water like foam board), it is still typically permeable, meaning the condensation will find its way trapped against the cold van wall either way. All of this could happen regardless of whether a vapour barrier is in place against the warm side of the insulation, because in this scenario I am including air that is already behind the insulation or finds its way in from outside (which you have to admit is highly likely).

    As a former house builder in the UK, interstitial condensation was always a big concern and misunderstood by many jobbing builders. Whenever a wall or roof structure contained a skin with low (or no) vapour permeability, a professional builder/specifier would assume that moisture would find its way to the cold (outer) side of any insulation (whatever insulation that was). So good building practice (and eventually regulations) would always mean leaving an air gap (e..g. partially-filled cavity wall with gap between hydrophobic wallboard and outer skin, and air gap above fibreglass insulation and roofing felt). In such cases a route would be made to allow ventilation across the surface of the insulation to avoid condensation and subsequent damp and rot. More modern building practices try to encourage the use of vapour permeable materials (like in the days of traditional solid-walled buildings). Only when all skins are vapour permeable, including the outer wall, is the need for air gaps reduced. But a van is not vapour permeable.

    Applying good building practices to a van would suggest insulation should not be stuck directly to the outer skin (i.e. metal wall) but that instead an air gap should be left with adequate ventilation provided across the cold side of the insulation (which should be vapour permeable but hydrophobic – such as foam board).

    This is why so many people correctly insist on a vapour barrier on the warm side of the insulation to prevent moisture getting into the insulation in the first place. But here I am talking about the almost inevitable air (and therefore potential moisture) that will get into it anyway, whether from a break in the vapour barrier or from outside.

    I really would be interested in your thoughts. Ideally I’d like to try out all of these combinations in real life, but who can afford the time and money to do that – other than a company interested in selling van (and boat) insulation solutions. But that is not me.

    For instance, if sheeps wool insulation really does have the potential to wick condensation away from a metal van wall, then yes we should avoid a vapour barrier and try to encourage the condensation to ‘dry out’ through heat and ventilation on the inside of the van. Though how realistic it is to ‘dry out’ condensation within the fabric of the wall from the ‘warm side’ before it causes damage is difficult to determine. It also goes against building regulations (at least in the UK) that specify a vapour barrier against the warm side of the insulation and no vapour barrier against the cold side.

    Sorry this is very long, but I have every other aspect of building a van sorted out in my head except insulation! Some may believe I am overthinking it. Many may not wonder what the heck I am talking about. But I know from experience that moisture can travel through paint, plasterboard, wood, insulation and concrete and wreak havoc. I have seen soggy, mouldy insulation extracted from both buildings and badly-built motorhomes!

    I put it to you that if so many people in the van dwelling community can get the use of Reflectix so wrong, then it is entirely possible that no one has fully thought through the implications of condensation in the context of insulation.

    Over to you!

    • Hi Paul,

      Thanks for the comment! No worries about the length – on the contrary, I thoroughly enjoyed reading it and I think it adds a lot of insight to the discussion here.

      I tend to agree with your conclusion – that the implications of moisture management, different insulation materials, and methods of installation have not been fully thought through or scientifically tested within the van community. Similar to Reflectix, there is a lot of opinion and “prevailing wisdom” floating around out there – some of which, on further reflection, may have potential flaws. Our goals with the first iteration of this post were to compile useful information on the commonly used van insulation materials, and to present the different schools of thought on how best to insulate a van. Alongside this we inserted our opinions at the time, and tried to label them as such, since we have not conducted our own hands on research all of the different insulation materials.

      But as you say, there is a whole lot of opinion about insulation in the van community, and not a whole lot of research and data. I’ve thought a lot more about this since we originally published this post, and we’ll be updating this post in the near future to reflect some updated thoughts.

      I agree that foam board insulation (and any impermeable insulation) carries the risk of being installed incorrectly and trapping air behind it, which could cause pockets of condensation to form. This, to me, implies that breathable insulation materials and proper ventilation are ultimately the best way to go. My thought process is that you won’t necessarily be able to avoid moisture condensing on the metal van walls no matter what you do – the trick is to make it so the moisture has a way out and doesn’t become trapped. Van interiors are typically coated/painted against rust, so condensation probably won’t automatically cause rust issues – but condensation that’s trapped without a way out might. What that means in terms of the optimal material (i.e. thinsulate vs sheep’s wool vs rock wool, etc) I think still remains to be investigated.

      But then the issue of cost comes into play. While someone could shoot for the best possible insulation scheme using the best possible materials, some of these materials cost a whole lot of money and are not accessible for the average DIY builder. The advantage of something like foam board is that it’s relatively inexpensive and it’s very effective as a thermal insulator.

      So that brings other questions to my mind – foam board may end up having some issues, but are they disqualifying? How big of a risk is there of rust developing from condensation that finds its way behind the insulation? And how do we balance that against the relative cost of different insulation methods for the average builder that may only have a few thousand dollars to work with? I think some of these questions still need to be definitively answered. Not to mention, there has been some concerning research that’s come out recently about the potential harmful health effects of various foam (and other) insulation materials that I think need to be evaluated and considered.

      Jayme and I plan to establish a part-time home base at some point in the near future, and once we do we have a dream of buying some cheap old vans that we will use to actually test various insulation materials (as well as other aspects of van building).

      Thanks again for commenting! Please keep this thread going if you have more to discuss, and feel free to share any helpful resources about insulation that may help illuminate different aspects of this discussion! Cheers!

      ~John

      • Hi John. Thanks for the full reply. I’ll look forward to your follow-up post!

        Due to the relatively low cost and high performance of foam board, my current thinking is to install foil-faced foam board on battens such that there is an air gap (25-30mm) between the metal van wall and the cold side of the foam board.

        Note that this gives the added benefit of reflecting radiant heat back outside to help keep the van cool in warm weather (might need to paint the inside of the metal van wall black if it is a reflective white so it isn’t bounced back again, trapping warm air in the cavity!).

        If I didn’t feel it appropriate to introduce ventilation from the outside of the van into the cavity formed between metal panelling and insulation, which would be ideal to my mind, I would consider introducing strategic ventilation holes through the inner van wall (ie though the wood and insulation) to the cavity. So no vapour barrier. After all, if we accept that inside the living quarters on a cold day it is still necessary to vent out nice warm air in order to control moisture, then allowing the cooler air behind the insulation to be vented out the same way (eg through a fan-assisted roof vent), is even less of a big deal. Of course, by doing this, I am accepting that water vapour will enter into the cavity and could potentially condense on the van walls on cold days, so will be planning its management through active ventilation and ensuring any drain holes in the van at the base of the wall are not covered.

        Note that if I also install battens on top of the warm inner face of the foam insulation boards to leave an air gap between them and the final finish, I am also benefiting from the reflective properties of the foam board to keep radiant heat in the van.

        Keeping all of the radiant heat in the van on a cold day (or out on a hot day) via reflection means the foam board has less work to do in trying to slow down heat transfer via conduction. This is why the likes of Reflectix is so efficient when used with an air gap (as much as 97% of radiant heat is reflected back).

        You know what, there may even be a case for forgetting trying to slow down the heat transfer out of, or in to, the van via conduction using foam board insulation, and just (correctly) use a suitable radiant barrier (eg Reflectix) in conjunction with battens that allow a healthy air gap between both the radiant barrier and the metal van wall (including any struts) and the radiant barrier and the final finish of the inner wall (eg ply lining). Leaving out say 50mm of foam board from the structure would help where space is limited. Adding some thermal bridging material where the battens are affixed to the inner metal struts would be a good idea. Hmm. I think a test is in order using an IR camera so see what additional thermal insulation foam board makes over and above correctly installed radiant heat insulation. If you get those cheap vans first and try it out for yourself, please do let me know!

        Paul

  • 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?

    • Hi Amy, reflective insulation needs to be exposed to air in order to have any benefit. This type of insulation works by reflecting radiant heat (think of the heat radiating off of a fire), which can only be transmitted through air or a vacuum. If you cover the reflective surface with fabric, then it can no longer reflect radiant heat. Hope that clarifies!

      ~John

  • 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.

    • Hi Peter, thanks for reading! We have not considered this type of insulation, but we’ll keep it in mind and look into it when we update this post in the near future. Thanks for the suggestion!

      ~John

  • 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 well use polyiso or something like that?
    What are you thoughts on reflectix straight onto the floor metal, then thin beams in the deep parts of the channels that are a little higher than the high parts of the channels, then ply etc to sit on top of the beams, given that that will produce a gap/cavity of sorts for the reflectix to work?
    Thanks again!

    • Hi Adam, glad you enjoyed the article! I think you’d be better off using rigid foam board (polyiso or XPS) rather than trying to mess with Reflectix and air gaps – it will be easier, cheaper, and will provide better insulation. You can get foam board as thin as 1/2″ if height is your concern. We used Reflectix on our floor, but we only did so to get some sort of insulation under there (about R-1) without taking much away from the height (I’m 6’2″, so I feel your pain). While it’s better than nothing, it’s not really proper insulation. Reflectix is great as a reflective window covering and for adding a radiant barrier to cavities, but behind the walls and under the floor I think foam board makes much more sense. As far as insulating the floor channels, that’s something you could also do with foam board if you don’t want to mess with spray foam. I would leave the channels directly underneath the walls empty, though, to make sure there’s an escape path for any condensation that makes it behind the walls. Hope that helps!

      ~John

      • Thanks for this! I’ll probably follow this exactly. What are your thoughts on ‘underfloor heating’? for example if i were to run piping in the channels on the floor of the van for example, then fill it with hot water somehow? this would surely stay hot in all that insulation and i could maybe have the end drainable out the back door for when it’s eventually cold. Do you think there would be any benefit to something like this?

  • 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 wrap, or to tape it to the metal surfaces/ribbing.

    If I am allowed to post links here, I can link to additional information. In the meantime, if someone is interested in either sheep wool insulation or thin foil-faced cotton duct wrap, feel free to ask.

  • 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?

    • Hi Annalise, thanks for the kind words! We have not compared the acoustic properties of these materials yet, but we plan to do so when we update this article in the near future. Thanks for the suggestion!

      ~John

    • 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.

      • Hi DHK, thanks for commenting! I agree that sound deadening is very important. We neglected to sound deaden our first time around, and immediately regretted it when we heard the road noise on the highway. When we redid our flooring, we took the opportunity to lay down some Peal ‘n’ Seal material for sound deadening and it made a world of difference.

        While foam is poor at sound insulation, you can easily apply sound deadener material like Noico or Peal ‘n’ Seal prior to applying foam. All insulation materials have pros and cons. Foam does not offer sound insulation and has some emerging environmental concerns, but it is cheap and very effective at thermal insulation. Thinsulate is a very interesting material that offers excellent moisture management, but is outside the budget range for many DIY builders. We think it’s important to understand all the properties and tradeoffs in order to make the best decision for your build.

        Thanks again for offering your insight to this discussion!

        ~John

    • Hi Lataa, unfortunately we don’t know anyone off the top off our heads. There are several vanlife-related Facebook groups that you can pose this question in, and hopefully someone there would be able to help. Best of luck!

  • 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 confused. I ask because I have cardiac and respiratory issues and mold and mildew is a huge problem for me. Also, I’m on a very tight budget and while I don’t mind paying a little more to get it right, I must get it right the first time, This is a bucket list project and I don’t have the time or the budget for second chances…

    • Hi Kevin, getting things to conform to curvy walls is certainly one of the great challenges of building a van. Layering 1/2″ sheets would make it easier for them to conform to the walls, but would likely be quite a bit more expensive than buying thicker sheets.

      Rock Wool is definitely an interesting option for vans and should be easier to get it to conform. My understanding of how it responds to moisture is that if water is splashed onto it, it will roll off, and it will float in a swimming pool. But that it is vapor permeable, and can potentially hold on to water vapor / condensation that makes it to the insulation. The Rock Wool itself is nonorganic and should not provide food for mold, but any dust or organic material that finds its way into the wool could breed mold. Rock Wool is certainly much more mold resistant than most other forms of insulation, especially batt insulation. Given your health concerns around mold, it might be a good idea to contact the manufacturers directly and get some details about how Rock Wool might respond to a high condensation / humidity environment like a van. Of course, adding a vapor barrier and making sure you have good ventilation (vent fan) will go a long way towards mitigating any issues. Hope that helps!

      ~John

  • 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 Cara, thanks for commenting and glad the article was helpful! R-value is a measure of a material’s Resistance to heat transfer. The higher the R-value, the better a material is at resisting heat transfer, and the more effective it will be at insulating. R-value can change with the material, and it can change with the thickness. For example, 1/2 inch of Polyiso is about R-2.5, whereas 1 inch of Polyiso is about R-6. The higher the R-value of the walls/ceiling of your van, the better your van will resist heat penetrating from the outside in the summer, and heat leaving your van during the winter. Hope that helps!

      ~John

    • Hi Kim, spray foam expands to many times its original size as it cures (much more than you think it will). Installing it can be very messy, and if you overdo it you could end up with mounds of foam where you don’t want it. Cleaning it up and shaving it down can be very time consuming and messy, and it’s very difficult to remove spray foam from fabrics (or any other surface). That said, if you’re careful and have the budget it can be a good option. Hope that helps!

      ~John

  • 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 and all around one of the best I’ve read. (Shh don’t tell anyone I said that, I try to be impartial ) ok well thanks for sharing your story! Happy vanning ✌️

    • Hi Nikki, thanks so much for the kind words! And you’re right about the Great Stuff – it expands way more than you think it will, so if you’re not careful you’ll have a lot of excess foam to shave off the next day! We just insulated a buddy’s van and did a much better job with the foam then we did with ours. The key is to just use a little bit and trust it to expand. You can always add more after it sets. Also watch out for foam seeping out of the spray tip!

      ~John

    • Hi Steve, glad you liked the article! We haven’t looked into hemp insulation in too much detail, but it looks interesting. We’ll definitely check it out for a future update of this post. Thanks for putting it on our radar!

      ~John

  • 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?

    • Hi TAK, you are correct, radiant barriers need an air gap to be effective. If you glue the reflective side of the polyiso directly to the van skin it won’t act as a radiant barrier at all, but polyiso is an effective insulator even without the radiant barrier. We installed our polyiso with the radiant side facing towards the interior of the van, but we put our walls right on top of it. The bigger issue with many van builders misusing radiant barriers is with Reflectix, since Reflectix has almost no insulating properties and is really only a radiant barrier.

      I just looked into Prodex, and it’s a similar idea to Reflectix, only it’s foam core instead of bubble wrap. Many manufacturers of reflective materials like this grossly overstate the R-Value (Prodex claims R-17 for the 10mm version). What they don’t tell you is that to achieve this R-Value, you need to install it with a sizable air gap. By itself without the radiant barrier, this product is likely not much more than R-1. With the amount of air gap you would need to bump up the R-value, you would be much better off filling that with good foam board insulation.

      Hope that helps!

      ~John

  • 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 to use polyiso, but the thickest I’ve seen it is 2″. Maybe I could stack it, gluing up multiple layer of thinner material to match the contour? ($$$ & work)
    So thinking denim. Any ideas??
    Primarily a California vehicle with the very occasional road trip.
    Much appreciated.

    • Hi Ian, glad you liked the article! The curved walls of the average van definitely adds some challenges. That’s crazy that yours has 4″ of rib space in the middle! Ours (’96 Chevy) has maybe 1″ all the way up, and the ribs follow the contours of the walls.

      The issue with denim as I see it is that it’s absorbent and can be prone to mold, but that may not be a huge deal if you’re staying in drier climates. If you’re not planning on doing a lot of winter camping, then you may not need to insulate the entire wall cavity – instead, you could go with 1″ of polyiso, and maybe think of ways to repurpose all that space in the middle as some sort of storage. If you do want to insulate the entire cavity, you could consider looking into spray foam or wool insulation. Either of these would be easier to fill the whole cavity than foam boards. Havelock Wool is based in Tahoe, also.

      I hope that helps, and best of luck!

      ~John

      • Hi John, thanks for your help. Wool it is. Here’s my plan : attach 1-1 / 2 ” furring strips horizontal along walls ( air gap ) to attach 1/2″ foam board foil side out as a radiant barrier, then the rockwool insulation, then some reflectixs for vapor barrier and climate control. Then paneling. Maybe tung and groove boards. All smooth wall, no cabinetry. Am I over thinking the insulation? Thanks, Iain.

  • 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

    • Hi Simon, so glad you found the article helpful! Rockwool or spray foam are good choices for filling your frame (just be aware that spray foam expands drastically). If you fill it well and seal it off with aluminum tape you shouldn’t have to worry about moisture, condensation in there (foil is an excellent vapor barrier). Reflectix does have its uses (it’s great for window coverings), but there is a lot of misinformation out there so many DIY van builders end up using it incorrectly. Hope that helps!

      ~John

  • 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?

    • Hi Greg, thanks for commenting! To answer your questions:

      1. You could do it either way, but I tend to think it’s better to be able to access wiring if needed. We didn’t run the wiring beforehand (we weren’t quite ready for that step), but we did tape up some flexible tubing/wire conduit where we planned to have wire runs, insulated around them, then later ran the wiring through. We wrote a bit about this in our first insulation post. We only really had to worry about this for the ceiling lights – all of our other wiring we ran through parts of the frame, or did not interfere with insulation.

      2. We did not do this in our van, but adding a layer of insulation over the ribs should increase the total R-value of your van. Doing so would also take up additional interior space, so there is a tradeoff, and unless you’re spending a lot of time in extremely cold temps you may not want to give up the space. In warmer climates, ventilation, shade, and reflective window coverings will be more important for the internal comfort of your van.

      3. You can fill the channels/ribs with batting, spray foam, rock wool, or anything you’re able to shove in there. We used fiberglass, but would not do so again.

      Hope that helps, and best of luck with your build!

      ~John

  • HI!
    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

    • Hi Gil! We actually just recently put sound deadening on the wheel wells and under our floor (read more here). When we initially did our build, we neglected sound deadening and immediately regretted it due to the road noise. But it’s all fixed now! 🙂

      As far as why we chose Reflectix – we went with that for our entire floor because it offers R-1 without an air gap (better than nothing!), it’s only 1/4″ thick so it takes up less height in the van, and on the wheel well specifically there’s a good amount of open space around it so we do see the benefit of the airgap there. We think Reflectix can be a good choice for areas like door panels and wheel wells where you’re more likely to benefit from an airgap. We decided to only use spray foam to fill in gaps and cracks due to the messiness and the cost, but it can certainly be a good choice for van insulation.

      Hope that answers your questions!

      ~John

      • Oh it is John. So informative. I am just starting my DIY conversion of my newly purchased 2006 140″ sprinter. And it’s very exciting. But that’s it, i have done research for many days now about the insulation and almost ready to order my materials and begin. I’m anxious in a good way!
        Your article helped a lot, I’m still left with few small questions.
        First couple of details, I ordered 2 maxxair fans. And the van will be traveling all over America, north central and south, for a full time living. So I expect to spend time in some very hot and very cold environments as well. Maybe equally. but definitely a lot of hot.

        I want to put 0.5″ of XPS in floor, 3/4″-1″ of polyiso in walls and 1.5″-2″ polyiso in ceiling. As you guys recomended and mainly because of its R value. But I am not sure about it, maybe it would be better to put 2″ polyiso on ceiling and 1″ XPS on walls? I can’t afford thicker insulation in the rear big windows because I am doing a widthwise bed and i might just fit in.

        I suppose you see the benefits of sound deadening material. I thought about Norco. What do you think about it? I am slightly on the fence here too because i heard some people aren’t sure how much it really changed. they were saying that the insulation itself(thinsulate in their case) made the environment quiet.

        Lastly, when I glue the boards, should i use closed cell foam? Is the material I glue the boards different than the material I spray in the far to reach cavities or are those two different things?

        Thank yo very much for taking the time to help me chose the insulation. I will serve me for years.

        (Excuse my English, i’m from Israel)
        Kindly,
        Gil Gofer ([email protected])
        🙂

  • 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, depending on where the van is going to live.

  • 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 start with a passenger or conversion van, and just remove the extra seats and move your camping interior in, it will save some big $$$, and the hardest work will already have been done for you. A $20 fan in an open window is at least as efficient as a $200+ roof vent with a fan, and it won’t leak later on down the road. Putting holes in your roof is never a good idea, for any vehicle. Sooner or later, they always leak, and windows offer much better ventilation anyway.

    Ventilation is essential in any RV or camper van. Even in the winter, ventilation is required to combat moisture and mold problems. Insulation offers little to no value for temperature control when ventilation is required, which is pretty much always. Beating hot or cold weather is relatively easy, but insulation for temperature control is a waste of time and money. Most passenger vans are already pretty well sound proofed for passenger comfort, so extra insulation for sound deadening usually isn’t needed.

    I mentioned indirect swamp coolers, and an explanation should be added, because direct swamp coolers only work in low humidity areas. Indirect swamp coolers were designed to work in the high humidity swamps, and will work anywhere. Both intake and exhaust air is vented outside, and only the cold water created by that process go inside, through a small radiator like a heater core, with a fan attached to blow the air through it. This method adds no moisture to your interior, and the result is very close to that of a much more power hungry compressor type air conditioner, and will work even in high humidity areas. These do not require ice, only water. As I write this it is 90 degrees outside in the shade, and 87% humidity. Inside my van, it is 70 degrees, and 38% humidity using an indirect type swamp cooler. I have to cycle it on and off to keep it from getting too cold inside. Some sort of thermostat would be a welcome improvement, but that is above my skill level. On high, it draws a total of 3 amps at 12 volts. My van does not have factory air conditioning, and this swamp cooler keeps me comfortable while driving too. Summer in southern Florida is easy breezy with an indirect type swamp cooler, even if I’m forced to park in the sun.

    As a fulltimer, interior climate control is one of the most important factors in your overall comfort levels. Insulation only slows down mother nature, it takes proper equipment to truly keep you comfortable. Insulation is optional, proper equipment is not. Your life can depend on your choices, because both heat and cold can be killers. Heating and cooling power is not the place to cheap out, trust me, every year people die from both the heat and the cold, don’t be one of them.

    PS: I have a window van, with no added insulation, and I don’t insulate my windows either summer or winter. Having good heating and cooling methods beats trying to rely on insulation alone big time. We all run into nasty weather sooner or later, and need to camp out inside the van sometimes for multiple days. I had a heavily insulated cargo van, and insulation alone didn’t cut it. It was always too hot or too cold. My window van requires far less heating and cooling power, and no need to run lights during the daytime either. The view makes life a whole lot more enjoyable too.

    • Hi Van Dweller,

      Thanks for the input! I agree that insulation alone doesn’t cut it most of the time, but I think insulation definitely has value, particularly in cold weather. And if you use rigid foam board insulation (polyiso or XPS), it’s entirely possible to fully insulate a van for less than $100.

      We insulated and built much of our van in the dead of winter, so we have direct experience of what the inside of our van was like before and after insulating. After installing the insulation, the inside of our van was significantly warmer, and working on the interior in a t-shirt was comfortable even in sub-freezing temperatures. I should also mention that when we gutted our van there was pretty much zero insulation behind the factory walls – just a very thin layer (maybe 1/4”) of some sort of fiberglass material.

      We haven’t experienced Alaskan winters, but we’ve lived in our van in the New Mexico high desert in late winter/early spring (10-15 degree nighttime temps), and northern New England/upstate New York in winter (very cold all the time). In addition to our insulation, we keep our windows uncovered during the day to allow sunlight in, and cover them at night with reflective insulated curtains (reflecting radiant heat back in). We also have an insulated curtain separating the cab from the living area to make the space smaller and further eliminate heat loss. Even when it’s below 20 degrees outside, the inside of our van never dips below 46 degrees (with a window cracked and box fan running all night)- which is a lot more comfortable than it sounds in a small space. With our insulation, we find that body heat alone is enough to keep the temperature comfortable, and we hardly every use our Mr. Buddy propane heater.

      In hot weather, shade and ventilation are insanely important. But even when we’re parked in the middle of a wide open parking lot during a hot day, with our insulation, reflective window coverings, and ventilation, we’re always able to keep the interior temperature at or below the outside temperature – which I think is pretty good for a vehicle without active cooling. But ideally we’ll be parked in the shade with our awning out and a shade cloth on the south side of the van – much more comfortable.

      Thank you for mentioning indirect swamp coolers! I had only heard of traditional swamp coolers before, and I’ve been kicking around ideas for modifying the concept to work in humid conditions. I’m excited to see that something like that already exists!

      ~John

    • 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.

  • 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!

  • 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!

    • Hi Molly, there’s zero squeaking sounds from our insulation while driving. When it’s installed, the foam is basically glued in with the gaps between them filled with spray foam, so it really should not be moving around. Foam insulation in general (boards, spray, etc) does help a bit with sound dampening, but if we did it again we would add some dedicated sounded deadening material directly to the metal van walls before insulating. We recently redid our floor, and we used this stuff called Peal and Seal for sound deadening, which is basically aluminum roof flashing tape that we picked up in the roofing section at Lowe’s. Home Depot sells a similar product under a different brand name. It made a huge difference, and you don’t need to cover every inch – just enough to add some mass and deaden vibrations. Hope that helps!

      ~John

  • 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?

    Thanks!

    • Hi Brayden, in general we’re not the biggest fans of fiberglass insulation, but it ultimately depends on you and your build. Fiberglass can be an inexpensive way to insulate, but there are some cons to be aware of. Like you mention, you’ll want to make sure it’s completely sealed off from your living space so that no fiberglass particles get into the air. A good way to do that is to cover the fiberglass with trash bags. Fiberglass also tends to be a bit thick, so using it in your walls may take away from interior space. That said, it’s super cheap and widely available so it may be the right choice for you as long as you’re aware of the drawbacks. Hope that helps!

      ~John

      • This is super helpful! I recently got some leftover fiberglass batting that was otherwise headed to the dump, and it’s enough to insulate most of a van. I knew that wool was the best option but free is a significant cost savings. I’ll probably use it for the walls and something thinner for the floor and ceiling. I’ll have to do more research on moisture control. I appreciate this thorough rundown!

  • 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 Brandon, thanks for commenting! Sound deadeners like Noico work by dampening the vibration of the metal van body, so it needs to be put down directly on the floors/walls before you put down the Reflectix. Hope that helps!

      ~John

  • 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?

    • Hey there, thanks for the kind feedback! Let’s say you out sheet of foam insulation over the ribs to act as a thermal break. Basically, you would make sure to measure/mark where exactly the ribs are, then you can use longer screws to go through your walls (or whatever else you’re mounting), the outer layer of insulation, and into the ribs. So you can still mount things to the ribs, you’ll just have an extra layer in between – similar to screwing into studs through drywall in a house. There are probably a few other ways to approach this, but this is one option. This video by Cheaprvliving shows this technique in action. Hope that helps!

      ~John