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A Complete Guide to Campervan Insulation (2024)

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).


I'm Shane, I've been teaching people to convert campervans for years; I'm the author of Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan, writer of The Van Conversion Newsletter, instructor of The Van Conversion Course over at Udemy. And full-time vanlifer for 4 years!


Now let's jump in a look at the best campervan insulation!


This is the best van insulation

This post contains affiliate links, which means that if you click a product link and buy anything from the merchant (Amazon, eBay, etc.) we will receive a commission fee. The price you pay remains the same, affiliate link or not. By using these links, you are helping me to continue writing free educational content!


Index

 
 
Van conversion book

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...



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:


  1. Thermal properties: How 'insulating' is it?

  2. Ease of installation: Will it fit where we need it to go?

  3. Health risks: Will it cause itchiness / chemical off-gassing?

  4. Fire resistance: Is it flammable?

  5. Water absorption: Is it hydrophobic or hydrophilic?

  6. Eco-friendliness: Was it sustainably made / is it recyclable?

  7. 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%).


Most popular campervan insulation
Most popular campervan insulation; Roaming Home 2023 Study

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.


Best campervan insulation
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:


  1. Amount of heat transferred

  2. Distance between the two isothermal planes

  3. Area of the surface

  4. Difference in temperature


K-value (Imperial): BTU ÷ h × ft2 × °F K-value (SI - international) : W ÷ m × K


Thermal conductivity of various materials

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

  1. Conduction: The transfer of heat by direct contact

  2. Convection: The transfer of heat caused by the motion of fluid or gas

  3. 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...


Convection, conduction, radiation

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).


Thermal Bridging in a van
Thermal Bridging

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.


Van conversion air loops

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.


Air loops in gap in insulation


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.


Van conversion insulation barrier

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).


e-value of different 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.


Reflectix fan cover

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...


Where to use reflectix in a van

Option #2: Put wooden furring on top of Reflectix to create an air gap between the Reflectix and the wood panelling/ply.


Reflectix under furring

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).

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.


Roaming Home book

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.

@vandercamp_adventures
@vandercamp_adventures

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.


reflectix vapour barrier
Reflectix vapour barrier; Ducatodreams.com

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:

  1. Foam board

  2. Van insulation roll

  3. Spray foam van insulation

  4. 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:


  1. XPS board

  2. EPS board


In our 2023 study, we found that 21% of vans use polyiso board, 18% use XPS board, and 12% use EPS board.


polyiso vs eps vs xps

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

Polyiso foam board
Foil-backed PIR board

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


Effect of temperature on Polyiso
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.


Vanspace3D

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:


  1. Sheep's wool

  2. Mineral wool

  3. Fibreglass

  4. Earthwool

  5. Recycled plastic

  6. Recycled Denim


Batt insulation is excellent for filling awkward spaces in your van - you can stuff it places that board insulation couldn't go!


Van conversion Batt insulation
Earthwool roll


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).


best batt insulation

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.

campervan spray foam insulation
A great job with the spray foam; @goldenadvantures

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.


spray foam insulation
@cooaroo filling gaps with spray foam

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.


van conversion loose fill insulation

The following are the most common loose fill insulations:


  1. Cellulose

  2. Mineral wool

  3. Fibreglass

  4. 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.


van conversion insulation 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.


How to loose fill insulate a van

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:


  1. Reducing greenhouse gas emissions

  2. Using recycled or sustainable materials


Reducing greenhouse gas emissions


GWP of insulation
GWP of insulation

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.


Reflectix on van floor

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.