Choosing Insulation for Your DIY Campervan Build

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Let’s talk about insulation in your van. After figuring out your layout, this will be your first task. Whether you want to stay in warm or cold temperatures, it is your friend! In the summer, it will keep your van cooler for longer, conversely, in the winter, it will keep your van warmer for longer. This guide will help you determine the best insulation for your priorities, whether that be saving money, reducing toxicity, preventing moisture, or maximizing insulation properties. We will also answer several questions such as should you install a moisture barrier? Why does condensation happen in a van build and how can you minimize it? What the heck is thermal bridging and why does it matter? Let’s dive in!

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Principles of Heat Transfer in Your Van

There are three things you are battling when trying to regulate the temperature in your van: conduction, convection, and radiation. Conduction is the transfer of heat through contact. Convection is the transfer of energy through movement of a liquid or gas. Radiation is heat transfer through electromagnetic rays. There are ways to reduce each of these methods of heat transfer in your van. This post will mainly focus on the principle of conduction which can be greatly reduced through the use of insulation. Convection can be reduced through the use of fans, while radiation can be reduced through the use of reflective materials. Before we dig into how to insulate your van, we will discuss some pertinent topics to keep in mind.

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Thermal Bridging

This is real! Thermal bridging occurs when temperature travels through conductive surfaces past the insulation of your van. An example is when hardware like nuts and bolts have an unbroken thermal pathway to the outside. Unfortunately there is not much you can do about thermal bridging. You will want to limit the number of nuts and bolts screwed to the metal of your van that pass through your insulation.

Moisture Barriers: To Utilize in a Van Build or Not?

This is a controversial topic. It’s our opinion that you shouldn’t put a moisture barrier behind the walls of your van. An example of a moisture barrier would be house wrap like Tyvek. Your van is already a moisture barrier. When you add a moisture barrier, you are creating a gap between two barriers where moisture can collect. When you build your van, the humidity will not be zero meaning there will already be a certain amount of moisture present. You also run the risk of puncturing that barrier later and introducing more moisture to this space. Moisture trapped in between barriers can lead to rust and mold. The ideal, if you had enough space, would be to have an air gap with a way to circulate air, most van builds cannot make this sacrifice. For this reason, we do not recommend installing a moisture barrier.

Condensation

Condensation in your van is inevitable. Between breathing, dew point, cooking, and fuel sources, you will have moisture and condensation in your van. The question is, how can you minimze the amount that forms, and how can you eliminate it when it happens? Solving this issue is extremely important as condensation can lead to mold and rust in your van. The first thing we should discuss is the concept of dew point. Dew point is the temperature at which air must be cooled for water droplets condense. Dew point is dependent on the humidity in the air and temperature.

How to Reduce Condensation in Your Van

To reduce condensation, you can manipulate temperature and humidity in your van. By using high R value insulation, the temperature in your van will have less contact with the cold air outside therefore making the dew point lower. We have had direct experience with the impact of insulation on dew point. Initially, we did not insulate the cab of our van. We had condensation raining down in cold weather with water collecting on our headliner. We eventually adhered speaker carpet directly to the metal of the van. This provided a break and a small amount of insulation between the cold metal of the van and the inside environment. We also this increased the surface area allowing moisture to evaporate. So far, this has eliminated our condensation issues in the cab.

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The second thing you can manipulate is the absolute humidity in your van which will reduce the amount of vapor that will condense. One of the most important ways to do this is ventilation, this will remove the humidity produced in your van through breathing, cooking, etc. We recommend having two fans so that you can circulate air. We love our MaxxAir fans as you can change the direction of air flow to push or pull air into your van, creating circulation. Ventilation is especially important when it is cold out as you are closer to or at your dew point. Ventilating is also important in the rain because the humidity of the air is increased. One perk of the MaxxAir fan is that you can leave it open in the rain. We also added rain guards which allows us to crack our windows in the rain.

Other ways to minimize condensation are avoiding heating with un-vented propane and ventilate when you are cooking inside with propane. When propane is combusted, it releases 4 molecules of H2O into the air for each molecule of propane burnt! That is a lot of moisture to be released into the inside of your van. If you choose to heat with propane, choose a heater that vents externally. Additionally if propane is your fuel of choice for cooking, cook outside when you are able, and always make sure to ventilate when you cook inside. Even if you chose a non-propane fuel source for cooking inside, you will still want to ventilate as cooking releases humidity into the air. Finally, having a diesel heater, or a vented propane heater, can help dry your space and reduce moisture.

Sound Deadener

Before we even talk about installing insulation, we need to talk about sound deadener. Sound deadener needs to be applied directly to the metal of the van so you will need to apply it before beginning insulation. The exception to this is if you choose to insulate with spray foam, spray foam is it’s own sound deadener. Sound deadener can go a long way towards a peaceful nights sleep in your van. There are several peel and stick products that are made of highly viscoeleastic material. This means that when hit with a sound wave, it has a difficult time traveling through. Very little sound deadener is required to achieve this affect, you only need to apply it to 25% of a surface for it to reduce the travel of noise.

We used Noico sound deadener but there are several options on the market. When you apply the sound deadener, be sure to use a roller or other material to firmly press down and adhere the material. Noico has bubbles that when pressed in, tell you that you have fully adhered the product. We cut panels of approximately 25% of each metal panel in the van. We noticed a HUGE difference after we applied them, our van sounded like a tin can when we rapped on the sides, after application, the resonance of sound was greatly reduced. This also makes for a quieter ride.

Thermal vs. Radiant Van Insulation

There are two different kinds of insulation, thermal and radiant insulation. Thermal insulation is the reduction of heat transfer between objects in thermal contact. Thermal insulation has several different sub-categories which each have pros and cons of their own. Efficiency of thermal insulation is measured through R-value, the higher the R value, the better insulator the material is.

Radiant insulation works by reflecting radiant heat. The best example of radiant insulation is Reflectix. In warm weather, it reflects the radiant heat of the sun back out of the van. In cold weather, it reflects the radiant heat in your van back in. The problem with radiant insulation and where most vanlifers go wrong, is that it doesn’t work without an air gap. This means it loses it’s properties if it is pressed directly up against a surface. Many people install Reflectix right up against the wall of your van which is honestly doing nothing for you. Additionally Reflectix is a moisture barrier so if condensation gets between the wall of your van and your Reflectix, you have issues.

Where radiant insulation shines however is in window coverings. Making Reflectix window coverings can make a world of difference in warm weather. It also helps in cold weather if you have several windows in your van, so much heat is lost through exposed windows. So while we don’t recommend radiant insulation for the walls of your van, it does have it’s place in window coverings.

THERMAL VAN INSULATION OPTIONS

FIBERGLASS

R value: 3.7 per inch

Price: 0.64 cents per square foot

Toxicity: toxic when inhaled and installed, toxic when it breaks down over time

Resistance to moisture/mildew: absorbs moisture, risk for mildew

Fiberglass insulation is popularly used in home builds, it would stand to reason that it would be a good option in a van build. WRONG! Do not use fiberglass insulation in your van build. It may be cheap, but it has relatively low insulation value per inch comparatively. It is toxic when installed, you definitely do not want to breath this stuff in or get it on your skin. Additionally it breaks down with vibration, which your van will experience a lot of. When fiberglass breaks down, it releases harmful chemicals. Finally fiberglass insulation absorbs moisture and is not mold resistant which can lead to all kinds of problems. We mentioned fiberglass insulation first so we can tell you exactly why you shouldn’t use it in your van build. Now moving on to more viable options.

WOOL

R value: 3.6 per inch

Price: .83 cents/sq foot at 2 inches

Toxicity: extremely low

Resistance to moisture/mildew: absorbs moisture, mildew resistant

If you have the funds, wool insulation is a good option. It is eco-friendly, does not off gas harmful chemicals, absorbs moisture, and serves as a sound deadener. It offers less insulation value per inch than rigid foam and spray foam insulation. Unfortunately, wool is hard to find in stores and traditionally has been expensive to ship in small quantities. Lucky for vanlifers, Havelock Wool has worked to reduce these costs for those looking to insulate their vans with small batch wool.

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DENIM

R-value: 3.7 per inch

Price: .76 cents per square ft. at 3.5 inches

Toxicity: Non-toxic

Resistance to Moisture and Mildew: absorbs moisture and prone to mold

Denim is a low toxic option but it is on the more expensive side, additionally it absorbs moisture and can be prone to mold and mildew. It has a relatively low R value per inch. For these reasons we do not recommend insulating a van with it.

THINSULATE

R-value: 3.2 per inch

Price: $3.10/square foot at 1.5 inches

Toxicity: contains polypropelene which is potentially toxic

Resistance to Moisture and Mildew: does not absorb moisture and resistant to mildew

Thinsulate has one of the lower R values of the insulation options, for this reason, you will have to apply more layers of it to achieve the same results, it is also more expensive than most other options listed. It is relatively easy to install and can be stuffed in cracks. Thinsulate contains potentially toxic materials (though not as toxic as some other options). It does not absorb moisture but instead lets moisture move through it.

XPS- Extruded Polystyrene Foam

R-value: R5 per inch

Price: .63 cents/square foot at 1 inch, $1.13/square foot at 2 inch

Toxicity: high on list of toxicity, produces off gassing and is not environmentally friendly. Manufacturers of XPS use flurocarbons in the production of the foam board, these fluorocarbons can offgas and release greenhouse gases into the atmosphere. This is an unfortunate environmental impact of the installation of XPS.

Resistance to Moisture and Mildew: Moisture resistant and mildew resistant. Apply tightly to metal wall of van with no air gap to avoid moisture in between the metal and your insulation.

We used XPS in our van build. This was largely because you get the most bang for your buck insulation wise and it’s easy to work with. While Poly-Iso does have a higher insulating value in normal conditions, it’s performance deteriorates in extreme cold. At 15 degrees F, Poly-iso’s R value drops from R6.0 to R2.0! According to Owen’s Corning, the gases trapped in poly-iso begin to condense below 15 degrees fahrenheit, as they condense, the thermal conductivity of the polyiso increases causing cold temperatures to transfer through. If you plan to have your van in areas that are below 15 degrees F, we recommend XPS over Poly-Iso. We are not fans of the ecological impact of XPS however we plan to take our van to Alaska and having insulation that didn’t perform in cold weather wasn’t an option.

POLY-ISO

R value: R6 per inch above 15 degrees Fahrenheit, R2 per inch below

Price: .63 cents/square foot at 1 inch, $1.13/square foot at 2 inch

Toxicity: Low, Polyiso uses no fluorocarbons and no greenhouse gases

Resistance to moisture and mildew: Water resistant and mildew resistant. Apply tightly to metal of the van with no air gap to avoid moisture in between the metal and your insulation.

Poly-Iso has the highest R value per inch of all the options however it shrinks to the lowest R value below 15 degrees Fahrenheit. If you don’t plan to camp below 15 degrees F, Poly-Iso can be a great option for you. One thing to consider is that Poly-Iso has a reflective water proof film on each face which makes it a vapor barrier, if you want to install Poly Iso, make sure you apply it directly against the wall of your van without any gaps.

EPS- Expanded Polystyrene Foam (styrofoam)

R value: R 4.6 per inch

Price: .37 cents/square foot at 1 inch, .74 cents/square foot at 2 inch

Toxicity: low, does not use fluorocarbons

Resistance to Moisture and Mildew: degrades over time with moisture as it has air gaps within it, risk for mildew due to moisture

EPS is extremely cheap as far as insulation goes, it is basically styrofoam. Of the rigid foam options, it has the lowest R value. It also can be difficult to install as it is not as pliable and it prone to cracking around curvy walls. Additionally it can crack through movement. It is anoption for a budget van build but if you can afford it, we recommend other options.

SPRAY FOAM

R value: 3.6 per inch

Price: $9/square foot for professional installation $8/square foot to purchase 2 kits for DIY

Toxicity: high off gassing during application, low off gassing after curing

Resistance to moisture and mildew: Moisture and mildew resistant plus no risk of air gap being formed

The spray foam we are talking about here is the two part kit which is different than Great Stuff Spray Foam. Spray foam kits, when applied properly, can be an excellent method for insulating your van. You can hire it done professionally which can give you great results. We have heard mixed results with completing the job yourself, you will definitely want to read all the instructions thoroughly before tackling the job. Surprisingly, hiring the job done costs in the ballpark of what it costs to buy the materials yourself. Levi Allen has a great video detailing his process with his van.

One huge plus with spray foam insulation is it is it’s own moisture barrier and adheres directly to the walls of your van so you won’t have to worry about rust and mildew issues. It is recommended to have your wiring done prior and run in conduit in case you have to replace anything. In order for the spray foam to cure properly, you need to apply it in 60-90 degree temperatures, if you are doing a van build outside in temperatures cooler than that, you may be limited to when you can complete the job. Spray foam insulation is by far the most expensive option for insulating your van but if you have the funds, it can be a good option for eliminating the risk of mildew and rust behind your walls.

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The Verdict

Only you know what kind of insulation is best for your needs. There is no clear winner in all categories in our mind. Depending on your priorities, everyone will have a different answer that fits their needs. Below we will list the winner for each category, each option has it’s benefits and drawbacks.

Highest R value above 15 degrees F: Poly-Iso

Highest R value below 15 degrees Fahrenheit: XPS

Most environmentally friendly and low toxic: Wool

Cheapest: EPS

Most resistant to moisture/mildew: Spray Foam

Great Stuff Spray Foam

If you are using rigid board insulation, you always have areas where you can’t get your insulation. One option is stuffing those caverns with wool or thinsulate. You may have to purchase more than what you need which can end up costing you more. Another option, and the option we utilized in our van build is Great Stuff Spray Foam. Great Stuff Spray foam is a great option for filling large cavernous areas. It is expensive and messy and you will need more than you think, but it can give you great insulation results. We used about 20 cans in our van on top of XPS rigid board insulation. Spray foam can be extremely toxic during application so you want to be sure you are wearing a P100 mask and have adequate ventilation.

One thing to keep in mind during application is that spray foam does not expand or cure properly unless it is exposed to air and humidity. For this reason, you will want to apply spray foam in layers and not fill large cavernous areas all at once. This is a great video that demonstrates how to use steam while applying your spray foam to ensure that it cures. If your spray foam does not cure properly, not only will it not perform well, it can release harmful gases called isocyanate. Another consideration during application is that spray foam also does not cure unless it between 60-90 degrees Fahrenheit. We applied spray foam when it was not consistently warm enough and had spray foam gooping out in a few days when the temperature warmed up. Learn from our mistakes!

Insulating Your Van Floor

Depending on the height of your van and standing space, you may or may not want to insulate the floor of your van. If you have the funds and the height to spare, we recommend insulating the floor of your van, it will feel warmer on your feet and keep your van better insulated. We have a low roof van so we felt we couldn’t justify sacrificing the height for insulation. The best option for insulating your floor is XPS, it does not lose it’s insulation properties when it is compressed.

Minimizing Heat in the Summer

Much of the focus of insulation is keeping heat in when it is cold. There are several things you can do to keep your van cooler when it is warm. Having a full decked roof will reduce the amount of radiation heat transfer through the roof of your van. Parking in the shade can make a world of difference in the heat when you are able. The color of your van is a huge consideration, having a lighter colored van will keep your van cooler than a darker colored van. Utilizing Reflectix window shades can also reduce the amount of radiation heat transfer into your van. The Reflectix material reflects heat outwards and reduces the amount of energy transfer into your van from the sun.

Temperature control in a van can be a tricky topic, especially as most vans are not climate controlled. By utilizing insulation, you can keep your van warmer in the cold, and colder in the heat. Additionally, you can reduce the effects of condensation. We hope this guide has helped determine the right kind of insulation for your van build whether you are looking to reduce toxicity, save money, or maximize insulation properties. Be sure to subscribe for more van build tips and inspiration!