Van Insulation Guide: Best Insulation for Van Conversion
Choosing the best insulation for van conversion is a big decision. For something you’ll never see after van insulation has been installed it has a pretty big impact on your daily comfort.
Knowing where to start can be confusing – I’m going to break it down simply for you!
There are 3 main topics in this article:
- How heat transfer works. Understanding the basics will help you determine which insulation material you need. When you know the science behind how your van gets too hot or too cold, then you can find the correct insulation to prevent it.
- What to consider when choosing insulation. Is it efficient? What does it cost? Can it be easily installed? Etc.
- 9 types of camper van insulation. Their benefits, disadvantages, cost and any other important things to note.
I spent many hours in deep rabbit holes on the Internet before deciding how to insulate my van. I travel with my dog so being able to regulate the temperature in my van was extremely important to me.
Spoiler: I insulated my Ford Transit with 3M Thinsulate, XPS foam board and spray foam.
A well insulated van is something you’ll appreciate down the road (pun intended).
Why You Need Van Insulation
Before we jump into the best van insulation options, let’s take a quick step back and review why insulation is so important for a camper van, and how it works.
A basic foundation of the science will help greatly when deciding on the best van insulation for your build.
Science!!
Van Insulation 101
What Does Van Insulation Do?
Simply, it slows the transfer of heat. That is all. Easy-peasy.
A strong insulating material will transfer heat slowly and a poor insulating material will allow the transfer of heat more quickly.
When it’s cold outside and you want to keep heat in your van, your insulation is preventing the heat inside your van from transferring through your floor, walls, ceiling, windows and doors to the outside.
Conversely, when it’s hot outside, your insulation is preventing the heat outside from penetrating your van walls and getting inside, where you’d like to maintain a cooler temperature.
Heat Transfer Basics of Van Insulation
Heat transfer occurs in 3 ways: radiation, conduction and convection.
All 3 types of transfer will occur in your van. Having an understanding of each will help you determine which insulation material is best.
Radiation
Radiation occurs when heat transfers through the air.
Radiation heat is what you feel when you sit near a campfire. The fire isn’t touching you, but the heat from it is transferring through the air around you (just like the sun’s heat.)
Conduction
Conduction occurs when heat transfers through a solid material.
In a van, conduction happens when heat moves through the sheet metal of your walls.
The sheet metal doesn’t produce its own heat. Instead, when the sun heat hits the outside of your van walls you’re able to feel its warmth on the inside of your van because the sheet metal is transferring heat through conduction.
Convection
Convection occurs when heat transfers through movement in a fluid or gas. This is the principle that causes hot air to rise (because it is less dense) and cold air to sink (because it is more dense).
Heat is being relocated through the movement of air.
In a van, this is the reason why it’s warmer towards the ceiling and colder towards the floor.
Insulate Cargo Van Based on Heat Transfer Principles
Now that you know the ways in which heat transfers you can make an informed decision on insulation.
In order to prevent convection heat transfer through the van walls and ceiling we we need to insulate.
Windows can be covered with reflective material while parked to slow radiant heat transfer.
Lastly, a roof vent fan, like a MaxxFan, removes warm air raising towards the ceiling through convection air flow. The insulated ceiling will trap the warm air in (the same way it keeps the sun conduction heat out.) By using a roof vent we can optimize both types of heat transfer to our benefit.
R-Value
Insulation is measured by its r-value. R-value is a standard unit of measure that allows equal comparison of different types of insulation.
R-value indicates a materials ability to prevent heat transfer through itself. A high r-value insulation is more resistant to heat transfer (a better insulator) than materials with a lower r-value.
A note on r-value: R-value measures the heat resistance for 1-inch thickness of material. Typical r-values range from 2 to 6 per 1-inch thickness. Occasionally, some websites will publish r-value based on the total installation. This means they’ve multiplied the materials r-value by the thickness of the installation. For example, the wall of a building is 4-inches thick and uses insulation with an r-value of 4 (per inch). The r-value of the insulation in that application is a total of 16.
I’ve included a chart below that compares cost and r-value equally across all insulation types, based on 1-inch thickness.
Thermal Bridge
A thermal bridge is a weak spot in your insulation, like a gap or a seam, where heat transfer is greater than the areas surrounding it.
For your van insulation this just means you want to avoid having gaps in your insulation where heat can penetrate (like the ribs on your ceiling.) The more thermal bridges you have, the less heat resistant (ie. effective) your van insulation will be.
Vapor Barrier
This is the most polarizing topic within van insulation. Do you need a vapor barrier? Or does a vapor barrier do more harm than good? Internet creatures have a lot of feelings about this topic.
First of all- what is it? A vapor barrier is intended to keep moist air (like what you exhale) from reaching a cold surface (like the sheet metal walls of your van.)
When moist air contacts cool surfaces it creates condensation.
Eventually, water and metal lead to rust.
Supporters of a vapor barrier argue that preventing condensation from occurring on your van walls and ceiling will prevent rust. Thereby keeping your van in good working condition for longer.
The case against vapor barriers argues that while the concept is correct (and works for some applications – like a house), the reality for van dwellers is that it’s impossible to keep moisture from getting into your walls.
Water will get behind your vapor barrier eventually. Then it will be trapped by the vapor barrier.
Trapped water in your walls will lead to rust and mold.
For this reason, insulating materials that do not absorb or retain water are great for a van build.
A note on water leaks: My brand new Ford Transit came from the factory with a very small roof leak. Further proof that it’s damn near impossible to ensure no water ever penetrates your walls.
Verdict: Do not install a vapor barrier in your van. It is just additional cost and build time without any guaranteed advantages.
Tip: Use a roof vent fan, like a MaxxFan, to exhaust warm moist air out of your van. It’s a good idea to keep your exhaust fan open, even in the colder weather, to prevent condensation build up inside your van.
Things to Consider When Selecting Van Insulation
R-value
A higher r-value van insulation is more effective at preventing heat transfer through itself.
Pick insulation that has the highest r-value while still meeting your other requirements.
Cost
The cost of van insulation can range widely. However, the benefit to insulating a small space is that even if you select the most expensive option your total project cost will only be a few hundred dollars more than the most cost effective option.
Ease of Installation
Insulating a van is intimidating. There are tons of tight spaces, nooks and crannies and curves to work around. It’s far more complicated than insulating a flat, straight, square wall in a home.
Selecting a flexible insulation material will make the DIY van install process much faster and far less frustrating.
Flexible insulation materials include 3M Thinsulate, mineral wool, sheep wool, fiberglass, spray foam.
Vibration Resilience
Some van insulation materials will compress over time. This is expedited by the movement and vibrations of your van.
Insulation works best when it’s fully expanded. Once insulation is compressed it will lose effectiveness and its r-value will decrease.
Moisture and Mold Resistance
Van insulating materials that absorb or hold moisture will grow mold with time. Moisture in a metal van will also lead to rust.
The best van insulation material is one that is hydrophobic (repels water.)
Toxicity and Off-gas
Certain insulating materials will off-gas toxins. There’s conflicting data about how bad this is for your health.
Some insulation may off-gas for a short period of time after installation. Some may off-gas for longer. Some does not off-gas at all.
If you choose van insulation that off-gasses you’ll want to do your own research into the health concerns.
In homes, off-gassing materials are sometimes used with a vapor barrier, which prevent fumes from entering the home. If you won’t have a vapor barrier keep this in mind because your application will be different from what is typically discussed in forums and manufacturers websites.
9 Best Insulation for Van Conversion
3M Thinsulate Van Insulation
R-Value: 3.4 (marketed as 5.2 for 1.65”)
Effective against conduction heat transfer
Thinsulate is a synthetic insulating material created by 3M. It’s the same stuff that lines mittens, snow pants and other outdoor gear.
There are a few types of Thinsulate available. For insulating a van use SM600L. You’ll likely have to purchase online and have it shipped as it’s not standard in most stores.
Typically costs about $1.70 per square foot of 1.65-inch thickness.
Pros:
✅ Hydrophobic (water-repelling) / mold resistant
✅ Easy to install
✅ Conforms to tight spaces and curves
✅ Does not off-gas
✅ Sound deadening
✅ Fire resistant
Cons:
❌ Expensive
❌ Must be fully expanded to be effective
❌ Compresses over time
❌ Typically requires shipping, not available in-store
Recommended Use: Walls, ceiling, doors, cab headliner, tight spaces
Polyisocyanurate (Polyiso or ISO) Foam Board Van Insulation
R-Value: 5.8
Effective against conduction heat transfer
Polyiso foam board is a closed-cell insulation. Of all foam board options, polyiso is the most expensive and best insulating, except in colder temperatures. While most insulations work better in cold temps, Polyiso loses efficiency around 60°F.
Typically costs about $.70 per square foot of 1-inch thick foam board.
Pros:
✅ Hydrophobic (water-repelling) / mold resistant
✅ Does not off-gas
✅ Sound deadening
✅ Fire resistant
Cons:
❌ Not easy to install
❌ R-value will decrease in colder temperatures
Recommended Use: Walls, ceiling. Not recommended for vans intended to be in climates cooler than 50°F.
Extruded Polystyrene (XPS) Foam Board Van Insulation
R-Value: 5
Effective against conduction heat transfer
XPS is another rigid foam board option. It’s less expensive than polyiso, isn’t as effective at insulating and can absorb some moisture over time. Unlike other van insulation options, XPS is able to maintain it’s r-value under compression, which makes it a great option for insulating van floor.
Typically costs about $.42 per square foot of 1-inch thick foam board.
Check out the Insulfoam website for more information on rigid foam board types.
Pros:
✅ Hydrophobic (water-repelling) / mold resistant
✅ Sound deadening
✅ Compressive strength makes it a good option for floor insulation
✅ Fire resistant
Cons:
❌ Some off-gas
❌ Insulating properties stop at 165*F
❌ Production process is not eco-friendly
Recommended Use: Floors, walls, ceilings.
Spray Foam Insulation for Cargo Vans
R-Value: 6.5
Effective against conduction heat transfer
Spray foam is a liquid aerosolized form of two compounds that expand up to 60x when mixed. It is typically used as an insulator, and also has strong fire and vapor resistant qualities.
Installation is tricky because of how much spray foam expands, so most van lifers opt for professional installation.
Typically costs about $1.20 per square foot of 1-inch thickness, labor not included.
Pros:
✅ Hydrophobic (water-repelling) / mold resistant
✅ Conforms to tight spaces and curves
✅ Sound deadening
✅ Fire resistant
Cons:
❌ Difficult to install, may require a professional
❌ Off-gasses
❌ Expensive
❌ Some body shops may refuse to work on rigs with spray foam
Recommended Use: Walls, ceiling, doors, headliner
Mineral Wool / Rockwool Van Insulation
R-Value: 4
Effective against conduction heat transfer
Mineral wool looks similar to fiberglass. It’s made from rock materials and is known for having good insulating and sound deadening qualities.
Just like fiberglass, touching it with bare skin can lead to temporary itching.
Typically costs about $.80 per square foot of 1-inch thickness
Pros:
✅ Durable: R-Value does not deplete over time
✅ Hydrophobic (water-repelling) / mold resistant
✅ Does not off-gas
✅ Sound deadening
✅ Fire resistant
Cons:
❌ May cause itching during install
❌ May contain Formaldehyde
❌ Production process is not eco-friendly
Recommended Use: Walls, ceiling, doors. headliner
Sheep Wool / Havelock Wool Van Insulation
R-Value: 3.8
Effective against conduction heat transfer
Sheep wool is a natural wool insulation. It’s been good enough for Sheep for thousands of years, so why not a van?
In addition to being a natural resource with good insulating qualities, sheep wool is also a renewable resource which makes Mother Earth happy.
Typically costs about $1.50+ per square foot of 1-inch thickness
Pros:
✅ Absorbs harmful chemicals to improve air quality (formaldehyde, nitrogen dioxide, sulfur dioxide…)
✅ Fire resistant
✅ Renewable & sustainable
✅ Hydrophobic (water-repelling) / mold resistant
✅ Conforms to tight spaces and curves
✅ Sound deadening
✅ Easy to install
✅ Does not off-gas
✅ Natural
✅ Breathable
Cons:
❌ Expensive
❌ Must be chemically treated to prevent pests
❌ Typically requires shipping, not available in-store
❌ Stinks like a barnyard for up to a year
It’s Complicated: Both hygroscopic (water attracting) and hydrophobic (water-repelling)
Why is this important?
The outer surface of sheep wool has water repellent properties, which means it will not mold.
The inner fibers of sheep wool are water absorbing — up to 33% of its own weight in moisture.
This isn’t inherently a problem… unless you have a vapor barrier which prevents moisture from escaping.
Assuming your van insulation is breathable, the wools water absorption can actually be helpful! In high humidity your sheep wool insulation will absorb moisture from the air and store it. In dry air the wool will release moisture to help balance the humidity levels inside of your van.
Nature is cool!
Recommended Use: Walls, ceiling, doors, headliner
Fiberglass Van Insulation
R-Value: 3
Effective against conduction heat transfer
Fiberglass is one of the most common forms of building insulation. It’s made of fine glass fibers (causes temporary itchiness if touched) and typically consists of 30% recycled material which lends it to be one of the more eco-friendly insulation options available.
Unfortunately, fiberglass is prone to moisture retention which can cause mold and mildew problems. For that reason alone, it’s highly unrecommended for van insulation.
Typically costs about $.60 per sf
Pros:
✅ Inexpensive
✅ Sound deadening
✅ Fairly eco-friendly
✅ Fire resistant
Cons:
❌ Difficult to install
❌ May cause itching during install
❌ Absorbs moisture, prone to mold
❌ Disturbing fiberglass (vibrations, air flow from a moving vehicle) can cause fibers to become airborne and cause irritation in your lungs, eyes, and on your skin
Recommended Use: Not recommended for van insulation
Reflective or Foil Van Insulation (Reflectix, Low-E, EZ-cool)
R-Value: 1
Effective against radiant heat transfer
Reflective insulation, also called foil insulation, is made of two exterior reflective layers with an interior layer of bubbles, foam or another form of insulation suited for preventing conductive heat transfer.
In addition to slowing conductive heat transfer with the middle material, the reflective outside layers work by preventing radiant heat transfer.
Reflective insulation requires at least ¾ inch air space in order to be effective. This space is called dead airspace and it’s important that the air is still and not circulating in order for this insulation method to be effective.
In cold climates, you will still need a second form of insulation that helps prevent heat loss through conduction.
Typically costs about $.30 per sf
Pros:
✅ Durable
✅ Resistant to moisture, helps prevent condensation
✅ Easy to install
✅ Does not off-gas
✅ Very effective in warm climates
Cons:
❌ Not effective in colder climates
❌ Not effective in ventilated cavity
❌ Creates potential electrical hazard
❌ Less effective when dirty
It’s complicated: ☂️ Acts as a vapor barrier. See vapor barrier section above to determine whether this is a pro or a con for your van build.
Recommended Use: Window covers
Insulating or Ceramic Paint Van Insulation
R-Value: Inconclusive and unproven
Effective against conduction heat transfer
Insulating paint was initially introduced as an idea by NASA to help cool rocket ships upon reentry.
Ceramic paint – like Lizard Skin, or paint mixed with a ceramic additive – is now marketed as insulating. However, there have been no independent studies that have proven the effectiveness of insulating paints, and a few studies which show it has no measurable impact.
Typically costs about $.20 per sf
Pros:
✅ Durable
✅ Resistant to moisture, helps prevent condensation
✅ Easy to install
✅ Sound deadening
Cons:
❌ Less effective in colder temperatures
Recommended Use: Not recommended for van insulation.
Best Insulation for Van Conversion – By Area
Insulating Van Floor
Note: The floor of your van is the least important location to insulate. If you’re tight on headspace I highly recommend you skip insulating your floor and take back those few inches for headspace.
If you plan to insulate your van floor it’s important to use Extruded Polystyrene (XPS) Foam Board. XPS is able to maintain its insulating properties under compression. You will have a significant amount of weight on top of the insulation and using any other type of insulation will be pointless as it loses its ability to insulate under compression.
On my 2020 Ford Transit, the floor has ribs that run front to back and are about ¼” inch tall. I chose to cut strips of ½” inch XPS foam board to lay between the ribs, and then add a second layer ½” thick XPS foam board over the first layer of strips. If you plan to spend time in cold climates and have the extra headspace I would increase the second layer from ½” to 1”.
After I insulated the van floor I installed ½” plywood on top of the foam board. I used glue between the foam board and the plywood to prevent squeaks, but the plywood is held in place by gravity (and eventually by cabinets secured to the van floor and the walls.)
Insulation for Van Walls
There are several options for insulating van walls: Thinsulate, sheep wool, XPS foam board, polyiso foam board, spray foam and mineral wool.
The best option for insulating van walls is Thinsulate because of its high r-value (5.2), anti-mold characteristics and ease of installation in tight and curved spaces.
Sheep wool and XPS foam board are also good for insulating van walls.
While it’s possible to insulate with polyiso foam board, spray foam or mineral wool, it’s not as favorable as the previous van wall insulation options.
Van Ceiling Insulation
You can insulate a van ceiling with polyiso foam board, XPS foam board, spray foam, mineral wool, sheep wool or Thinsulate.
The best van ceiling insulation is XPS foam board or Thinsulate. XPS foam board is more affordable, has a better r-value and can bend slightly (very slightly, don’t go crazy) with the curve of your van ceiling. The curve will make installation slightly more difficult, which is why Thinsulate is also a great option.
During the summer your van ceiling insulation is the most important way to keep hot air out. Vice versa for winter.
Insulating the ceiling of your van is the most important area to insulate. Prioritize thicker insulation in your ceiling over thicker insulation in your floor.
Van Insulation – Doors
Van doors can be insulated with Thinsulate, sheep wool, mineral wool, spray foam or foil insulation.
If you plan to use foil insulation remember that it requires ¾” of dead airspace surrounding it in order to be effective, and that it does not perform well in colder climates.
Mineral wool is the least expensive option with the highest r-value. Like all options for insulating van doors it is hydrophobic and mold resistant – which is great for doors which tend to collect rainwater.
Van Insulation – Headliner Storage Shelf
The van headliner is a big source of heat transfer and it’s very important to insulate. The best insulation for a van headliner is spray foam, Thinsulate, mineral wool or sheep wool.
Thinsulate, mineral wool and sheep wool can be installed easily without having to remove the molded headliner. Mineral wool is the least expensive option and has the highest insulating r-value.
Van Window Insulation
Window covers are important for both privacy and preventing heat transfer. Many window covers are made from foil insulation that work by preventing radiant heat transfer. These are popular because they’re fairly easy to DIY, hold up well, and do a decent job at keeping the heat out. However, they’re less effective in colder temperatures.
During my first year in the van I used these inexpensive Ford Transit reflective window covers from Amazon for my front windows and windshield. For the price, they worked well enough until I upgraded to window covers from VanMade Gear.
An alternative option is to use Thinsulate. If you use the same Thinsulate you did for insulating your van (SM600L) you’ll need to sew a back onto it as one side is exposed. If you use Thinsulate AU4002-5 both sides are enclosed so you can trim it to size and stitch the boarder closed.
I used Thinsulate AU4002-5 to make insulating window covers for the back windows in my van.
Best Insulation for Van Conversion – By Price
The cheapest way to insulate a van is to use XPS foam board. This gives you the best insulation from heat transfer for the lowest cost.
The chart below shows the price per 1” thick square foot of each van insulation material compared to it’s r-value. The last column shows the price for square foot of each material given an r-value of 1 so you can compare the cost of each material equally.
| Van Insulation | Cost per 1” thick square foot | R-Value per 1” | $ per R-value of 1 |
|---|---|---|---|
| XPS Foam Board | $0.42 | 5 | $0.08 |
| Polyiso Foam Board | $0.70 | 5.8 | $0.12 |
| Spray Foam (without labor) | $1.20 | 6.5 | $0.18 |
| Mineral Wool | $0.80 | 4 | $0.20 |
| Fiberglass | $0.60 | 3 | $0.20 |
| Foil Insulation | $0.30 | 1 | $0.30 |
| Thinsulate | $1.10 | 3.4 | $0.33 |
| Sheep Wool | $1.50 | 3.8 | $0.39 |
| Ceramic Paint | $0.20 | ? | ? |
Conclusion
What is the Best Insulation for Van Conversion?
Best Insulation for Van Conversion- Best Overall
The best way to insulate a cargo van is with Thinsulate. Thinsulate van insulation does not absorb water, will not mold, is non-toxic, very easy to install and conforms easily to van contours and curves.
While thinsulate is one of the pricier van insulation options, it’s a minor budget increase considering the small amount of space to insulate in a van.
Best Insulation for Van Conversion – Best Budget Option
XPS foam board is the best camper van insulation on a budget. As one of the least expensive options, it’s also one of the most effective types of insulation for a van.
XPS foam board is also best for insulating a van floor. Van floor insulation must be able to maintain its effectiveness under compression and XPS foam board is the only van insulation which meets this requirement.
Runner up: Polyiso foam board. Polyiso foam board gets strong marks for van insulation because it is both inexpensive and an effective insulator. However, polyiso is not an ideal van build insulation given that its ineffective in colder temperatures (below 50*F.)
Best Insulation for Van Conversion – Best Natural Option
Sheep wool van insulation is the best natural option. Sheep wool has a slightly higher r-value to Thinsulate but absorbs moisture and has an unpleasant smell that can take up to a year to dissipate. Keep in mind that typically it is treated with chemicals to prevent pests.
Best Insulation for Van Conversion – Best Insulating Properties (R-Value)
The highest rated r-value van insulation is closed-cell spray foam.
Spray foam van insulation has an r-value of 6.5. All of the other cargo van insulation options have an r-value of under 5, except Polyiso foam board which has an r-value of 5.8.
Planning a van build?
I have tons of resources and guides to help you navigate your van build choices, pick the best materials for your needs and provide inspiration, lessons learned, and tips from life on the road.
Check out these additional resources
Written by Claire Fleming
I’m a travel enthusiast who spends half the year in my self-built camper van with my dog, Oscar, and the other half at my home in Raleigh, North Carolina or on international adventures.
