No insulation in your van? This is you in winter: ⛄
We all like building snowmen, but I'd rather not be one!
Van conversion insulation is ABSOLUTELY CRITICAL to building a cosy campervan. In this guide we will look at the best campervan insulation on the market. You will learn the theory behind van conversion insulation and installation instructions for van floor insulation (as well as the walls and roof).
Insulation is a central component of preparing your campervan for winter. Read more about campervan winterization here.
I’m Shane, a van conversion professional dedicated to helping people transform ordinary vans into homes on wheels. I've authored Roaming Home, and teach The Van Conversion Course, guiding many people through their van builds. I also write The Van Conversion Newsletter, where I share practical tips and insights. After completing two van builds and living on the road full-time since 2020, I’m excited to share my expertise with you.
Now let's jump in a look at the best campervan insulation!
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Index
Spoiler: This is the best campervan insulation
We're going to be diving deep into all things insulation in this article - giving you a very thorough understanding. But if you want to cut right to the chase...
I recommend using Polyiso foam board for most of the big exposed areas in your van. It is particularly useful for van floor insulation and for the roof. You can use insulation stick pins to install the foam board. Alternatively you can use 3M Thinsulate.
For the tight areas / air gaps, I recommend using 3M Thinsulate, Hempitecture HempWool or Spray foam.
I recommend installing a draught excluder to stop heat transfer around the doors.
You should make sure you to have reflective window covers.
You should also consider using reflectix as a vapour barrier - but only if you're going to do a kickass job!
Now then, let's dive into campervan insulation in a lot more detail!
What is insulation?
Insulation is any material that is designed to prevent heat transfer - that is the movement of air from hot to cold. This could be for the purpose of keeping your van cosy in winter (keep the heat in), or to keep it cool in summer (keep the heat out!).
What to consider when choosing camper van insulation
There are 7 things we should consider when choosing van conversion insulation. They are:
Thermal properties: How 'insulating' is it?
Ease of installation: Will it fit where we need it to go?
Health risks: Will it cause itchiness / chemical off-gassing?
Fire resistance: Is it flammable?
Water absorption: Is it hydrophobic or hydrophilic?
Eco-friendliness: Was it sustainably made / is it recyclable?
Cost: Everything comes at a price...
In the Roaming Home 2023 study. We found that recycled plastic was the most popular insulation (41% of vans), followed by polyiso board (21%).
Best camper van insulation
Below is a table comparing almost every van conversion insulation on the market. Throughout this guide we will explore the pros and cons of each option and discover the best campervan insulation.
A crash course in insulation theory
Before we hop in and look at specific insulating materials, it is important to understand some of the key concepts behind the surprisingly complex world of insulation.
Thermal conductivity (k-value)
Everything in the known universe has the ability to conduct heat, that is the process by which heat is transferred from the hotter end to the colder end of an object.
Different materials conduct heat at a faster or slower rate depending on their thermal conductivity. A lower thermal conductivity (k-value) results in a lower rate of heat transfer. A lower thermal conductivity (k-value) will yield the best campervan insulation.
Formula: The formula for thermal insulation takes in four parameters and results in a single value known as the k-value:
Amount of heat transferred
Distance between the two isothermal planes
Area of the surface
Difference in temperature
K-value (Imperial): BTU ÷ h × ft2 × °F K-value (SI - international) : W ÷ m × K
From the table above, we can see that wool, air, and styrofoam are excellent insulators while the materials at the top (brass, copper, etc.) are very poor insulators.
The key takeaway here is that metals are very poor insulators - heat can pass through them easily, so we need to make sure to use the best campervan insulation possible (and to install it correctly) to prevent this! The most surprising takeaway of all is that glass has a far better thermal conductivity than steel! Steel is terrible.
R-value
R-value refers to a material’s ability to resist heat transfer at a certain thickness. It takes the K-value and the thickness of the object into consideration. A higher R-value will yield the best campervan insulation.
R-value (imperial): h × ft2 × °F ÷ BTU R-value (SI - international) : K × m2 ÷ W
To convert R-SI to R-imperial, multiply the R-SI by 5.68.
R-value is the most common value we refer to when discussing insulation.
Heat is transferred in 3 ways
Conduction: The transfer of heat by direct contact
Convection: The transfer of heat caused by the motion of fluid or gas
Radiation: Heat that travels through an object in the form of waves / particles (eg. the sun)
In order to get the best van insulation our goal is to reduce all three of these factors as much as possible. Let's explore...
1. Conduction
By understanding K-values and R-values we already have a good understanding of how to reduce conduction to give us the best van conversion insulation.
By putting an insulating material on the bare metal of the van, we can slow the transfer of heat by conduction.
It is important that we insulate as much of the van as possible - anywhere left un-insulated or with very poor insulation will act as a thermal bridge. A thermal bridge is an area of an object which has higher thermal conductivity than the surrounding materials; ie. allows heat to pass more easily. It is the path of least resistance and usually where we haven't insulated (eg. wooden support furrings or metal struts).
2. Convection
Most of us know that hot air rises while cold air sinks; this is known as convection. This happens because hot air is less dense than cold air. High pressure also moves in the direction of low pressure.
Air loops
Inside the hollow structures of a van (such as inside the metal support frames), this movement of air causes a phenomenon known as air loops. Warm air rises up by convection, then cools and drops as it comes in contact with a cold surface by conduction. This causes a circular/looping movement of air.
Air loops can greatly affect the efficacy of van conversion insulation. To get the best campervan insulation we need to reduce air loops as much as possible.
In practice, this means filling any cavities in the van with insulation to reduce the effect - this is normally done with insulation batts (discussed later). Make sure you fill the cavity as fully as you can, for air loops can still occur around the insulation if it doesn't fill the entire area. Be careful though - if you're using insulation batts (eg. mineral wool) make sure you don't 'squish' it and make it dense as this would reduce the R-value! Leave the insulation nice and loose and fluffy.
Draught exclusion
Another place we typically find convective heat transfer is anywhere air can flow from the inside to the outside of the van. Apart from the obvious fan in the roof, the air gaps around the side and back doors allow a large amount of heat transfer to occur.
In order to get the best campervan insulation possible, we need to cover these air gaps as much as possible! The air gaps around doors are particularly malicious when there is a large temperature difference between the inside and the outside of the van.
There are three ways you can block a draught in a campervan:
1. Furniture
The best way to block air flow through the door gaps is with a physical barrier like furniture. For example in my van, I built benches/storage at the back doors (after a year on the road) to stop the draught. I noticed a huge difference in van temperature after I built these.
2. Draught excluders
Draught excluders are the bomb! They are a really cheap and effective way to stop heat transfer. In fact these alone could be 'the best campervan insulation'. So do yourself a favour and grab a set!
3. Tapestries / Wall hangings
This simple hack can make your campervan a lot warmer! Hang tapestries over the side and back doors to stop the draught and act as an insulator. The thicker the tapestry, the better the draught exclusion. You can hang the tapestry up using screw hooks.
3. Radiation
Radiative heat transfer is a process where heat waves may be absorbed, reflected, or transmitted through a colder body. Hot bodies emit electromagnetic heat waves - eg. the sun. In fact all bodies emit radiant heat according to Planck's law.
Some materials are particularly good at preventing radiative heat to pass through (white / reflective materials), while others are very poor (glass / black materials).
Emissivity (e-value) is the value given to an object to describe how susceptible it is to emitting/absorbing heat. The e-value is a scale from 0 to 1; a lower number means a material will absorb less heat.
In order to get the best campervan insulation possible, one should also consider radiative heat transfer.
In practice, this means using a reflective material like Reflectix or Low-E to reduce radiative heat transfer (e-value = 0.03). This is like the foil material they use on spaceships! You can also buy foil-faced PIR foam board.
We can use Reflectix in three places to get the best insulation possible:
1. Window covers
Because glass has one of the very worst e-values, it is imperative that we cover it up to slow the heat transfer. You can make DIY window covers by cutting some Reflectix and attaching some suction cups to the corners. As a winter vanlifer, I can tell you first hand the importance of window covers! Do it! Else, you can purchase nice -premade window covers.
2. Fan cover
After you install a fan, you are going to have a hole in the roof that air can pass through; even worse, since hot air rises a lot of it will escape through the fan. To counter this you can make a fan cover using reflectix, or buy one online.
3. Thermal bridges with high e-values
As mentioned before, a thermal bridge is a weak spot in your van, through which heat escapes more readily. This could be exposed metal, or it could be an exposed/uninsulated timber frame (furring) that directly touches the outside of the van. The windows/fan would also be thermal bridges, but we have discussed them already. You can cover these high-e thermal bridges with Reflectix to slow heat transfer.
Note: Reflectix has been the cause of much controversy in the van conversion community. A few years ago a plethora of people started using it as insulation even though the R-value is practically non-existent. Luckily this carry-on has mostly stopped.
Here is the important thing to know: Reflectix will only reflect heat if there is an air gap! This means there are only two ways you can use Reflectix correctly:
Option #1: Put Reflectix directly on thermal bridges (metal/furring) and don't cover it with any wood panelling/ply. The entire van is then the 'air gap'. Understandably, this isn't for everyone as it can make your van look a bit gross. But if you really want the best campervan insulation...
Option #2: Put wooden furring on top of Reflectix to create an air gap between the Reflectix and the wood panelling/ply.
Thermal imaging
Reddit user u/PlasticBarista borrowed a thermal camera to see how his campervan fared. The results were fascinating.
Here are the key takeaways from the thermal imaging:
The thermal bridging of the wooden furring is clearly visible. Everywhere the wood touches the metal, heat is escaping.
More heat escapes up high, rather than down low.
A lot of heat escapes through gaps in doors, particularly high up in the van. The top of the back doors seem to allow the most heat to escape.
A lot of heat escapes through the glass and through the roof fan (not shown in the photos above). So I recommend installing a fan cover.
Note: While a lot of heat escapes through the glass, it still has a far better K-value than steel. Glass ≈ 1K, Steel ≈ 45K. Therefore, our highest priority is still insulating the body of the van. Though, we should also use insulated window covers.
Moisture control
The topic of Reflectix leads us nicely onto moisture control - a very very important thing in a campervan. Let's cut straight to the chase...
It is imperative that you keep moisture as low as possible in a campervan!
Doing so increases the life of your vehicle, improves the efficacy of some types of insulation, and decreases the chance of health-harming mould/rot.
There are four things you can do to reduce humidity / protect a van from moisture:
1. Keep it warm inside!
The first, and most important way to control moisture in a campervan is to keep it warm inside! Warm air can hold more moisture than cold air, which means that instead of water condensing on the metal of the van, it is held in the air. Mould/rot form when water is present on insulation for too long. If your heater has a thermostat on it, leave it on the lowest setting as much as you can during wet/cold months!
2. Ventilation
Ensure you have ample ventilation inside! Optimally, you want at least one air inlet and one air outlet to allow proper ventilation. This could be a fan and a sliding window, or something similar.
It is common to install a floor vent in a van, this allows you to take in cool air from under the van during the summer months.
3. Buy a dehumidifier
I have a dehumidifier in my campervan and it has been a lifesaver during the wet months. It just sits there, running silently, sucking water out of the air! Simple and effective!
4. Use a vapour barrier
Vapour barriers are another controversial technique used in van conversion insulation. When done right they are highly effective, when done wrong they are detrimental.
A vapour barrier is a material that wraps the van conversion insulation and is designed to prevent moisture from getting into the insulation (preventing mould and improving insulation). Some people choose to use polyethylene sheeting as a vapour barrier, though it is more common to use Reflectix as it can double up as a radiative heat transfer barrier on exposed surfaces.
In theory vapour barriers can be super effective. The problem is that most people will probably not get a 100% seal and this causes a big problem as water in the insulation gets trapped and can't escape!
So...
Only install a vapour barrier if you are absolutely sure you can get a 100% seal. Else, it is better to just let the insulation breath.
Note: There has been some worry in the van conversion community that installing a vapour barrier can trap moisture at the time of installation. But as Greg Virgoe debunks in one of his excellent videos, even on the soggiest of days, this only amounts to about 5ml - a teaspoon of water! So this should not be a worry.
Types of insulation
There are many types of insulations used in residential and commercial projects. However for the purpose of van conversion insulation, we can concern ourselves with just four:
Foam board
Van insulation roll
Spray foam van insulation
Loose fill insulation
Let's explore each of those...
Foam board
Foam board insulation is an incredibly popular form of van conversion insulation due to its efficacy. It is a rigid panel of insulation that is made of either polystyrene, polyisocyanurate, and polyurethane.
There are three types of foam board insulation:
XPS board
EPS board
In our 2023 study, we found that 21% of vans use polyiso board, 18% use XPS board, and 12% use EPS board.
Pros
Foam board is an excellent insulator (has some of the highest R-ratings)
Foam board has good resistance to mould (water resistance)
Foam board is a rigid surface that is excellent at preventing air leaks
Foam board is frequently lined with a reflective foil which lowers its e-value and reduces moisture uptake
Cons
XPS and EPS foam board insulation are a bit of an environmental disaster (hydrofluorocarbons)! Polyiso is much better though.
Can be more expensive than other types of insulation
Brittle
What is the best foam board insulation?
Polyiso board (PIR) is the best foam board insulation, and one of the best van conversion insulations overall. It has a very high R-rating, is fire resistant, and is a lot better for the environment than XPS. The best known polyiso board manufacturers are Kingspan, Ecotherm and Celotex.
If you want information on the specific differences between these insulations, check out this video:
Since foam board is probably the best campervan insulation, I suggest using it as much as possible: on your floor, roof, and walls. You can stick the board insulation to a surface using insulation stick pins (more on insulation installation later!).
The effect of temperature on Polyiso
Most insulation products actually perform a bit better the colder it gets but polyisocyanurate breaks that rule. Below 15°C its performance starts to deteriorate badly. By the time you get down to -20°C it has lost a huge amount of its insulating capabilities. It is a great product to use as long as you keep it warm, which is a really odd thing to say about an insulation product.
Having said this, I have used Polyiso in my van in -20°C. So long as I keep it warm inside, I have found it to work just fine.
Van insulation roll
Van insulation roll (also known as / similar to blanket or batt insulation) is woolly in texture and usually comes in rolls. The following are all types of batt insulation:
Sheep's wool
Mineral wool
Fibreglass
Earthwool
Recycled plastic
Recycled Denim
Batt insulation is excellent for filling awkward spaces in your van - you can stuff it places that board insulation couldn't go!
What is the best van insulation roll?
3M Thinsulate insulation rolls and Hempitecture HempWool are likely the best batt insulations on the market.
3M Thinsulate is very malleable, has a high R-rating, is water resistant, and poses no health hazard. I suggest getting yourself some rolls of the stuff and using it to fill any awkward spaces in your campervan. It is particularly useful for filling any air cavities in the van (to prevent air loops). Some people insulate their entire van with Thinsulate (and don't bother with any foam board). However I recommend using mostly foam board and fitting batt insulation in the cavities & smaller places.
In the Roaming Home study, we found recycled plastic to be the most popular batt insulation and fibreglass to be the least popular (for good reason).
Hempitecture HempWool is another excellent insulation option. It's a sustainable choice that stands out for its health and environmental benefits. Made from 90% natural hemp fiber, HempWool is not only safe to handle without gloves but also boasts no volatile organic compounds (VOCs) or toxins. Its superior thermal properties ensure no slumping or sagging, effectively maintaining your van's temperature throughout the year.
Spray foam van insulation
Spray foam van insulation is polyiso foam in a can. It is an expanding insulation that is rather satisfying to use and a powerful insulator! As the foam expands, it forms little bubbles/pockets known as 'cells'. The Roaming Home study found that 16% of van conversions use spray foam.
Pros
High R-value
Fits in tight places
Air barrier
Cons
Expensive
Health hazard when installing
Long time to install
Very permanent
Bad for the environment
Closed-cell spray foam can cause 'super-heating' which could cause bulging/warping of the metal of your van. Don’t go too crazy with the spray foam. In extreme cases, it can actually pop the panels off the ribs.
Many people in the van conversion community choose to insulate their van entirely with spray foam. You can do this yourself (with great care), or you can get a professional to do it for you.
There are two types of spray foam van insulation;
Open cell spray foam
Lower R-value than closed-cell (R-3.8)
Better for the environment
Closed cell spray foam
One of the highest R-values on the market (R-6)
No bueno for the environment
Doesn’t allow water to pass through. If you do a good job spray foaming your entire van, you may not need a vapour barrier
Safety note
Using spray foam van insulation can be a serious health hazard so make sure all your skin is covered and you are wearing a high quality mask/goggles when installing. Spray foam off-gases for a few days, so ensure good ventilation during installation and for the following days. It becomes safe when stable.
How to use spray foam
Ensure the surface you are spraying is clean, shake the can thoroughly, then spray! Make sure you cover the ground with a tarp as spray foam drips.
Spray foam van insulation expands ~30X its liquid size (high expansion foam can expand up to 300X!). So be conservative with your spraying. Apply constant pressure and spray evenly over the surface - don't spray too much.
You can use vertical or horizontal strokes to apply the expanding foam. Here's a video showing the different spraying techniques you can use.
My thoughts: Expanding foam is tricky to use. I recommend sticking to foam board and batts. But if you do choose to use it, I recommend getting a professional to do it for you. The experts should get a clean, airtight finish and you don't have to deal with the mess or off-gassing.
Where Expanding foam can be useful is filling the hard-to-get-at gaps in your van where you can't even fit batt insulation.
Loose fill insulation
Loose-fill insulation is not commonly used in campervans, however it can be a great alternative insulation and is good at filling up little gaps. It is the most environmentally-friendly way to insulate your van!
Loose fill insulation is similar in texture to batt insulation except it is 'loose' rather than coming in rolls. You can simply grab a handful of it.
The following are the most common loose fill insulations:
Cellulose
Mineral wool
Fibreglass
Sheep's wool
Pros
Environmentally friendly
Fits in tight places
Cons
Hard to install
Susceptible to moisture - need vapour barrier
Can be a messy installation
How to use loose-fill insulation
First staple garden netting (or insulation netting) tightly to the wooden frame/furrings of the van. Make sure you leave no gaps! The loose-fill insulation fills the gap behind the netting.
Using a box knife, cut a small hole in the netting where you want to insulate first, then feed the loose fill insulation into a leaf blower and blow the insulation into the cavity. Tape up that hole and move on to the next place.
Here is a great video on how to install loose fill insulation in a van.
The environmental impact of insulation
The environmental impact of insulation has become a hot topic in recent years. Many homeowners these days are trying to achieve high energy-ratings, typically through proper insulation. This makes the home more environmentally friendly and can actually increase the value of the home!
However, blindly insulating your home with whichever insulation is at hand is not the answer. There are very distinct environmental differences between insulations.
When considering the environment in choosing an insulation, we typically consider:
Reducing greenhouse gas emissions
Using recycled or sustainable materials
Reducing greenhouse gas emissions
Some types of insulation have a notoriously bad manufacturing process which emits a huge amount of greenhouse gas. One of the very worst being XPS foam board.
The best method we currently have of measuring greenhouse gas emissions is the GWP (Global Warming Potential) rating.
It is important that we choose an insulation with a reasonably low GWP.
The lion’s share of insulation emissions come from foam insulation. In order to expand the foam, harmful blowing agents are used. Hydrofluorocarbons being the most well known and most harmful. The F-Gas Regulation 517/2014 bans the use of HFCs with a GWP >150 in the manufacturing of all foams as of January 2023.
Using recycled or sustainable materials
Another environmental factor to consider when choosing an insulation is the use of recycled or sustainable materials in the manufacturing process. Insulations such as recycled denim, recycled plastic, cellulose, or wool are prime examples.
Health risks of insulation
It is important to consider the health risks when installing and living with insulation. Many types of insulation can be quite harmful.
Asbestos
The most harmful of all insulation is asbestos. It has a handful of side effects, including cancer. It should never, ever be used. It is rarely seen anymore.
Fibreglass and mineral wool
Fibreglass and mineral wool should not be used in campervans. This is because the shaking of the vehicle causes glass to come loose and become airborne. Many brands of fibreglass contain formaldehyde, a known carcinogen. There has also been some data come out recently about the adverse effects of mineral wool, with workers handling the compound being at risk of developing acute symptoms as well as developing harmful long term health conditions.
Spray foam
Spray foam exhibits a lot of off-gassing for a few days after installation. It can be a serious health hazard during this time due in part to the blowing agents, though it becomes safe when stable.
Insulation with fire retardants
Many insulations have added fire retardants to improve their fire rating. Many of these fire retardants are harmful to health. For instance, boric acid is typically added to cellulose insulation. Many types of foam insulation also have fire retardants; Polyiso boards contain TCPP. XPS and EPS boards contain polyFR, an eco-friendly alternative to HBCD that also poses grave health risks.
What should I do with this information?
I know… that was a lot of really unpleasant information. I’m sorry to have to lay that on you! Here’s what you can do to mitigate the dangers of insulation:
Make sure you wear appropriate PPE gear when installing insulation; mask, gloves, goggles, and protective clothing
Ensure good ventilation in the area you are insulating in the days surrounding the work
Ensure the insulation is sealed behind a protective barrier - a vapour barrier does the job perfectly
Optional: Get a professional to do the job for you. Your health might just be worth it!
Fire ratings of insulation
All insulations are (should be) given a fire rating. This describes how safe the insulation is. The most established fire rating system is the Euro class system.
The Euro class system compares ignitability, flame spread, heat release, smoke production and propensity for producing flaming droplets/particles.
The classification covers three aspects:
The first letter gives a classification based on the combustibility and contribution to fire: A1 and A2 are non-combustible. B, C, and D have a medium contribution to fire. E and F are easily flammable.
The ‘s’ part relates to the total smoke propagation/emission level. The values range from 1 (absent/weak) to 3 (high):
s1 = a little or no smoke
s2 = quite a lot of smoke
s3 = substantial smoke
The ‘d’ part indicates the ‘flaming droplets and particles’ during the first 10 minutes of exposure. The index is:
d0 = none
d1 = some
d2 = quite a lot
In a nutshell, we should check to ensure our insulation has a good fire rating before purchasing it. Do not rely solely on the insulation comparison chart in this chapter; the same type of insulation can have very different fire ratings depending on the manufacturer.
Now then... Let's dive into campervan insulation installation! Starting with campervan floor insulation.
Campervan floor insulation
Step 1: Lay strips of Reflectix (optional)
In many vans there are troughs and ridges in the floor (Ford Transit). Because of this, if we place foam board insulation directly on the floor, there will be many air pockets present underneath. We can fully utilise these air pockets by laying down Reflectix to lower the e-value of the floor and trap some air between the floor and the foam. This will give us the best van floor insulation
Make sure you use foil tape on the ridges between the troughs to get a complete seal.
Step 2: Lay down wooden furring beams
The next step is to lay the foundational wooden furring. Place the wooden frame all around the perimeter of the floor and then proceed to run lengths of it horizontally and vertically on the floor. I recommend using more wood rather than less on the floor. We screw our floorboards and furniture into these beams - it gives the rest of the van structural integrity. So don't be shy!
Note: Ensure the height of the wooden furring matches the height of the insulation you will use. For example, I used 5cm polyiso board (Celotex), so I made sure to use 5cm wooden furring.
Here’s how to install wooden furring for van floor insulation:
2.1. Measure your van floor and determine where you will be placing the furring strips. Then draw up a floor plan with all the measurements. In the best case scenario, you will already know (and have marked on the floor with tape) where your furniture will go. In this case, you can install the wooden furring exactly where you plan to screw the furniture down.
Draw the beams on the floor plan, including a unique letter/number corresponding to each beam.
2.2. Head into the workshop and cut the beams in batches using a circular saw. After cutting a beam, write the letter/number that it corresponds to with a Sharpie.
2.3. You can stick the furring to the floor using a glue like sikaflex. Just run lengths of the glue along the ridges of the floor and stick the wood to it.
Step 3: Install foam board insulation
Next up is installing the insulation. I used polyiso board in my build. Though XPS is more typical for flooring due to its high crush resistance (25 PSI); but I urge you to consider the environmental impact of that insulation. I have found the polyiso board in my van to be very strong underfoot, with no problems over three years on.
Using the measurements from the floorplan, cut polyiso foam board to shape so that it fits into the furring cavities.
You can mark a straight line on the polyiso board using a chalk line. Then cut along the chalk line using a handsaw. Make sure you wear a mask when cutting the insulation!!
After you have fitted all the polyiso board, you may still have some gaps in places - where the timber is not flush with the foam board. In this case you can fill those gaps with some wool insulation or expanding foam.
Step 4: Install a plywood subfloor
The subfloor consists of sheets of plywood that go under your floorboards. Cut the plywood to shape (using a chalk line and circular saw) and screw the sheets into the wooden furring.. Place bricks on top of the ply to help the furring stick to the ground.
And that's van floor insulation done!
Van wall insulation
After the van floor insulation is done, it's time to move into the walls.
Step 1: Build the wooden support frame
First, we need to build a wooden support frame running up the sides of our van walls. Our cladding/ply screws into these beams to make a beautiful van interior. You can use 2x1 timber for the furring.
The timber is screwed upwards along the sides of the van. There will be three levels of timber (due to the curvature of the van): lower, middle, and upper.
You can attach the timber to the metal rungs of the van by drilling in self-drilling screws. Or you can do it the normal way and first drill a pilot hole in the wood/metal, then screw in a self-tapping screw. I actually prefer the second way (though it takes longer) as the screws are more sturdy once installed.
Step 2: Install polyiso foam board panels
Most of our van wall can be insulated with polyiso board. Cut the foam board to size with a chalk line and handsaw and stick it on as much of the wall as you can.
You can stick foam board to the walls of your van in three ways:
Insulation stick pins (recommended)
Double-sided sticky tape (VHB recommend)
Step 3: Fill the gaps with batt insulation / spray foam
Inevitably there will be gaps on the wall where foam board does not fit/work. Fill these gaps with batt insulation; 3M Thinsulate and Hempitecture HempWool are the absolute best option for this job. If there is any tight gap where Thinsulate or HempWool won't fit, you can use spray foam van insulation.
Remember our goal here is to insulate as many pockets of air as we possibly can. We need to prevent air loops in as many places as possible!
Step 4: Add a vapour barrier (optional)
The last step is to add a vapour barrier to prevent moisture from getting into the insulation. If you only used foam board/spray insulation (and not batt/loose-fill), you probably don't need a vapour barrier. Sheep’s wool also handles moisture well, it is resistant to mould and can help absorb moisture then wick it away when there's enough airflow to dry it out.
Remember, if you are going to install a vapour barrier, make sure you do it right! Else just let the insulation breathe...
You can use polyethylene sheeting as a vapour barrier, though it is more common to use Reflectix as it can double up as a radiative heat transfer barrier on exposed surfaces.
Cut lengths of Reflectix with scissors and stick it to the wall with foil tape. Make sure you cover every single gap and make it airtight.
Note: Make sure you have already run all your electrical cabling around the van to the relevant locations before installing the vapour barrier. Cut small holes in the Reflectix to allow the cabling to pop through, then foil tape it up.
Insulating the van doors
First remove any plastic/ply lining that may have come stock with the van. This gives you access to the interior of the door. Check the metal lining around the door (especially the top) to see if there are any air gaps where moisture could get in. If there are any gaps, seal them with tape, or do a super permanent job with metal epoxy putty.
Then fill the interior with insulation - polyiso and batt insulation should do perfectly. Finally add a vapour barrier to seal the deal (optional).
Wheel arches
The wheel arches are a rather awkward space in a van. There are a few different techniques you can employ to insulate them.
I built a wooden frame around each wheel arch, ply-lined it, and filled it with wool insulation.
But, if you want to get fancy and efficient, you could use the awkward space to house your water containers! Nomadic Supply sells these awesome pieces of kit!
Van roof insulation
Van roof insulation is similar (but easier) to van wall insulation.
Step 1: Install the wooden support beams
The first step is to install the wooden support beams along the roof (our ply/cladding screws into this). Make sure that the timber beam you use matches the depth of your foam board insulation. I used 5cm polyiso foam board, so accordingly I used 5cm timber.
You will find 4-5 metal structural support beams running up the length of your van. The wooden furrings will be bolted to these support beams. Drill into the metal support beams (size M6/M8) from each side of the metal so that we can slot a bolt through.
Note: You must slot a bolt right through the structural support, rather than simply screwing into one side of it. Screws are not designed for shear force, bolts are.
Drill the same sized hole (M6/M8) in the appropriate location on the timber furring and slot a long M6/M8 bolt through the wood and metal. Screw on a nut to secure it in place.
Note: Due to the curvature of the structural support struts, it is unlikely the wooden furring will sit flush when bolted on. I used a plane to remove some of the wood along the edge of the furring so that it could sit flush.
Step 2: Stick strips of Reflectix to the troughs in the roof (optional)
Like with the floor, there are ridges and troughs in the roof. There will be a small air gap in the roof when we install our polyiso board insulation; we can fully utilise this air gap (lower the e-value and create a small air insulator) by sticking Reflectix to the roof.
Step 3: Stick polyiso foam board to the roof
You can stick foam board to the roof of your van in three ways:
Insulation stick pins (recommended)
Double-sided sticky tape (VHB recommend)
Stuff any air gaps with 3M Thinsulate, Hempitecture HempWool or spray foam. Seal up any gaps in the insulation with foil tape and you're good to go!
Note: By this stage you will have already have run the wiring for your 12v LED lights.
How to insulate the bulkhead of a van
The bulkhead is the big cavity above the cab. It is a tricky shape to insulate. Here's how to do it...
Stick wood furring (same depth as the board insulation) to the roof and base of the bulkhead with Sikaflex (you will need to prop the roof furring up with something while it dries).
Stick polyiso board to the base and roof (using stick pins or similar). Alternatively, you could use spray foam, which will be easier to install due to the curvature of the roof.
Ply-line the inside of the bulkhead.
How to insulate the doors of a van
The back and side doors of a van can be another tricky area to insulate. Let's have a look at how we can insulate them...
1. The first step is to remove any plastic/ply lining that may have come stock with the van. This is so that you can get access to the interior of van door.
2. While you have full access to the interior of the door, check the metal lining around the door (especially the top) to see if there are any air gaps where moisture could get in. If there are any gaps, seal them with tape, or do a super permanent job with metal epoxy putty. You can learn how to use metal epoxy in this guide on repairing rust.
3. Fill the door up with insulation - polyiso and/or batt insulation will do perfectly. Then optionally add a vapour barrier on top. 3M Thinsulate would be perfect for the job.
Sound deadening
Vans can be noisy, rattly things when you are driving. Sound deadening matts reduce noise while on the road substantially. I definitely recommend installing some! You can about read how to sound deaden your van here.
Sound deadening matts are installed before you insulate your van.
Conclusion
And there you have it - that's the best campervan insulation for your van!
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If you're looking for some guidance with your van conversion, you might be interested in our book Roaming Home, or in our online course The Van Conversion Mastery Course. You'll learn directly from me how to convert a van into your dream home - no prior experience needed!
Until next time,
Shane ✌️