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 many years, I'm the author of The Van Conversion Newsletter, instructor of The Van Conversion Course, and the proud owner of a beautiful self-build campervan called Beans. Now let's jump in a look at the best campervan insulation!
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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.
For the tight areas / air gaps, I recommend using 3M Thinsulate or Spray foam.
Optionally, you can use reflectix as a vapour barrier - but only if you're going to do a kickass job!
Now then, let's dive into some theory followed by installation instructions.
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 the inside of 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 van conversion 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 safety 🔥: 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...
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.
Type ♾️ | R-Value (per inch) 🥵 | Flammable? 🔥 | Eco friendly? 🍃 | Cost 💰 | Waterproof? 💦 | Health Risk? 🩺 |
|---|---|---|---|---|---|---|
Polyiso (Foam board) | 6 - 7.5 | No | Yes | $$ | Yes | No |
Closed-cell Spray foam | 6 - 7 | No | No | $$$ | Yes | Yes |
High density XPS (Foam board) | 5.2 | Yes | No | $$ | Yes | No |
EPS (Foam board) | 3.1 - 4.3 | Yes | No | $ | Yes | No |
3M Thinsulate (Batt) | 3.8 | No | Yes | $$$ | Yes | No |
Sheep's Wool (Batt) | 3.6 | No | Yes | $$ | No | No |
Cellulose (Loose-fill) | 3.4 | Yes | Yes | $$ | No | No |
Mineral wool (Batt) | 3.14 | No | Yes | $$ | Yes | Yes |
Fiberglass (Batt) | 3.14 | No | Yes | $ | No | Yes |
Mineral Wool (Loose-fill) | 3 | No | Yes | $$ | Yes | Yes |
Fiberglass (Loose-fill) | 2.9 | No | Yes | $ | Yes | Yes |
Earthwool (Batt) | 2.5 | No | Yes | $ | Yes | No |
Recycled plastic (Batt) | 0.65 | No | Yes | $ | Yes | No |
A Quick 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.
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
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 to prevent this!
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 the R-value will yield the best campervan insulation.
The formula for R-value is Depth(m) / K-value.
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 cause 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 conversion 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.
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 [¹]. Be careful though - if you're using insulation batts (eg. mineral wool) make sure you don't 'squish' them and make it dense as this would reduce the R-value! Leave the insulation nice an 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 (we discuss fan covers later), the air gaps around the side and back van 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:
Option 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 to stop the draught. I noticed a huge difference in van temperature after I built these.
Option 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!
Option 3: Hang up a tapestry
This simple hack can make your campervan a lot warmer! Tapestries usually work best for the back doors of the van and are very easily installed. The thicker the tapestry, the better the draught exclusion. You can hang a tapestry up using screw hooks.
3. Radiation
Radiation 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[²].
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 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!
We can use Reflectix in three places to get the best campervan insulation:
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 easily make DIY window covers by cutting some Reflectix and attaching some suction cups. As a winter vanlifer, I can tell you first hand the importance of window covers! Do it!
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.
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 exposed/uninsulated timber frame (furring) that directly touches the outside of the van. The window/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.
A note on using reflectix:
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:
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 want the best campervan insulation...
2. Put wooden furring on top of reflectix to create an air gap between the reflectix and the wood panelling/ply.
Moisture control
The topic of reflectix lead 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.