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How To Insulate Your Van

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It can be difficult trying to live out of a vehicle in cold weather. However, if you do the proper research and construction you can live comfortably, even in sub-freezing temperatures. This article will discuss the best ways to keep heat trapped in your vehicle, and leave the cold air outside. We will break down and explain how to insulate your van against all three types of heat transfer, and the best materials for the job. Once the insulation is complete, read up on our tips outlining how to heat your van in winter.

Do you even need insulation?

This might sound like a silly question to ask… everyone insulates their van, right? Before we get into how to insulate your van you should ask yourself why you’re doing it. What type of environment are you going to be spending your time? The majority of the US gets cold in fall and winter for a large part of the year. If you plan to spend a significant amount of time in cold weather, you should insulate! Insulation will definitely help keep the cold air out and the warm air in.

On the other hand, if all of your time is going to be spent in the south; or if you are only using the van for a summer road trip, insulation might not be a good idea. You may want the opposite! A proper insulation install will trap heat in your vehicle whether it’s warm outside or cold. In this case, you will actually want to find ways of reflecting and blowing the heat back out of the vehicle rather than holding it in.

We’re going to save ways to keep your van cool on the inside for a different article. If you want to stay warm in the winter, keep reading!

The three types of heat transfer

There are three main ways that heat can transfer between the outside air and the inside of your vehicle: radiation, conduction and convection. If you want to keep your van as warm as possible throughout the winter, you will want to address all three.

Radiation

Radiation is heat that can be transferred between two areas without any contact to the heat source. This heat travels through the air or within a vacuum. The most notable example of radiant heat is from the sun. You can feel heat from the sun on your skin even though you are not touching the sun – that is radiant heat transfer.

How does this relate to a van? Heat coming straight through your windows and warming up a vehicle is an example of radiant heat transfer.

Conduction

Conduction is when warm molecules vibrate against cold molecules until they balance each other out.The process of conduction has the strongest effect when heat is transferred through a solid object. To put it in simply, the warm inside walls of your van transfer that heat to the cold outside environment. If you add insulation to make your walls less conductive, it will take longer for that heat to get outside.

Convection

Convection is when heat is transferred through movement of liquids and gasses. It occurs naturally when warm air rises and cold air falls. This is most noticeable on the inside your van. Why does that matter to you? If you’re not careful, all of the hot air that has risen to the top of your van will escape through the ceiling. Convection is the most efficient transfer of heat, so proper insulation of your ceiling can be even more important than your walls.

R-value

The goal of insulating your vehicle is to resist conduction. You want to make it as hard as possible for the warmth in your van to escape to the outside. Thermal resistance to conduction is called an R-value.

Different materials have different R-values. Aluminum siding has a very low R-value of R-0.6, so heat can transfer straight through it easily. Materials that have a higher R-value such as wool, which is rated as R-3.5, make it harder for heat molecules to pass through them and escape.

When building out your van, you want to insulate your ceiling, walls and floor with materials that have a high R-value.

R-value, Space, and Expenses

Living in a vehicle is a unique situation. In a perfect world, you could take the highest R-value materials, stack them a foot thick and hibernate in your van throughout the entire winter. Unfortunately, space constraints are a huge issue in the van world. Every extra inch of insulation on the walls is going to make your living area that much smaller.

Not only this, but we don’t all have unlimited funds to insulate our vehicles to the highest degree. Therefore, insulation becomes a delicate balance between R-value, space, and expenses.

We will measure R-value in terms of R-value per inch. This means how much R-value can you get out of one inch of material. If you stack a material to 2 inches thick, you get double the R-value! Checkout the chart below for the R-values of some common materials:

MaterialR-value per inchThickness for R-6Absorbs Water?
Polyisocynurate6.40.92 inNo
Extruded polystyrene (XPS)51.2 inNo
Expanded polystyrene (EPS)3.851.6 inYes
Yellow Spray Foam6.50.92 inNo
Thinsulate3.31.8 inNo
Fiberglass (rolls)3.31.8 inYes
Fiberglass (batts)32 inYes
Reflectix (no air-gap)16 inNo

Many insulation values referenced here came from BuildAGreenRV.com

Condensation

Condensation is a big factor for vandwelling. Any case where the warm interior air touches a surface that is colder, moisture from the air will become a liquid. A prime example of this is the windows. If it is 35 degrees out, your windows will be nearly 35 degrees as well, which would be much different from the 65 degrees in the van. Add to this the relatively high humidity caused by breathing, sweating and cooking; and condensation becomes nearly unavoidable.

There is an ongoing debate among vandwellers on whether it makes sense to seal off the walls with a watertight material before adding insulation. If moisture is allowed to build up within the walls of a van you may end up with mold or rust.

The problem with adding a vapor-barrier right up against the walls is that it’s very difficult to do correctly. If there are any slits or gaps in the material, moisture can get behind that and build up between the watertight surface and the wall. If this happens, there’s nothing you can do. You won’t know there’s moisture until it begins to rust, and good luck trying to get all the way back there in the future.

In our opinion, the best bet is to insulate with materials that are water-resistant and seal everything as much as possible so moisture doesn’t get back there in the first place. You definitely don’t want to use insulation materials that absorb water. Proper ventilation is key to reducing condensation. The topic of condensation could be a whole article in itself. Just be aware that your choice of material can play a big role in how warm and dry you will be.

Before you insulate

Before beginning the insulation process, we’ll assume your van has already been fully deconstructed. This includes removing any seating, or unwanted material from the walls and floor. All old rust spots should be removed and any gaping holes in the walls or floor repaired and sealed.

Have a plan for anything that might have to go behind the walls such as wiring or lighting. Ideally, you would have some of your wiring pre-planned and even installed. It will be much more difficult to try and hide wires or move things around if you wall everything up first.

Getting started

Now that we’ve got the technicalities out of the way here comes the good stuff. What should you use to insulate your van? The five main areas of focus are:

  • Floor
  • Walls
  • Ceiling
  • Windows
  • Sealing everything up

Insulating the Floor

Because heat rises, the floor is the least important part of the vehicle to insulate. Many people choose not to insulate their floor at all. Covering any holes in the subfloor will be of greater importance than laying insulation.

Pick a material that has a high R-value in the thinnest amount of space. Extruded polystyrene (XPS) has an R-value of R-5. It is a very dense material that would take a lot of weight to compress. Because of this, it makes the perfect material to build on top of. A ½ inch of material may be all you need to insulate the floor.

Once the material has been picked, it should be fairly easy to lay down the floor. When you get to sections that do not have perfect edges, lay down some cardboard and cut out the shape you need. Once a cardboard template has been made, trace the design onto the XPS or chosen material. This will allow you to accurately cut the necessary shape and it should fit almost perfectly. After the floor insulation has been laid down, seal up all of the seams with gorilla tape or equivalent.

Wheel wells will be slightly more difficult to insulate because of the odd shape. However, as a bonus to the insulation value, insulating the wheel wells will also decrease the road noise coming from the tires while driving.

There are many different methods to insulate the wheel wells. Peel and Seal aluminum rolls can be a cost-effective way to cover the area. If you want to go this route, cargovanconversion.com has a great step-by-step video. Other van dwellers have used bubble-foil materials such as Reflectix or InfraStop. None of those methods are going to have a great R-value but they will most certainly be better than bare metal. If you plan to insulate the walls with yellow spray foam this would also be the perfect material to use on the wheel wells.

Insulating Walls

Insulating the walls and ceiling is a very time consuming but important part of the build. Material choice is going to depend a lot on personal preference. Some vans are very square, so a ridged material without much bend to it will not be an issue. A van designed with more of a curve may require a more flexible material. 

Reflectix– (Airgap Necessary)

Reflectix is a popular material you hear about when researching van insulation. This material reflects radiant heat transfer meaning it needs an air gap in order to work as designed. Without an air gap, the R-value of Reflectix is a 1. With an air gap, Reflectix has an R-value of about R-3.

What this means is Reflectix is a good material to use anywhere there is an air gap (like a window); it is a poor material to choose anywhere there isn’t an air gap. In short, do not insulate your walls with Reflectix unless you plan on placing a sizable air gap in there. The company itself recommends at least a ¾ inch air gap between the Reflectix and the insulated area. This material will not work as intended when placed directly between two surfaces because it is not designed to prevent conductive heat transfer.

Ridged Foam Panel Insulation

Polyisocyanurate (Polyiso) – White Foam with Foil

Polyiso is an excellent material choice for insulation. It is water resistant, and slightly flexible so it can bend around curves. Polyiso is rated at an R-6. Many, but not all polyiso sheets come with foil on one side to reflect heat like Reflectix. If you are placing an air gap in your walls, this will give you a double dose of insulation bringing the value up to R-7. Even without the air gap, this is the best material in terms of conduction resistance per inch. Polyiso can be slightly difficult to find in stores and more expensive than some of the other foam materials. If you can afford it however, this is the one of the best ways to go.

Extruded polystyrene (XPS) – Blue and Pink Foam

Extruded polystyrene is the ridged pink or blue foam board you find in hardware stores. It has an R-value of R-5. With its high value, this is another great choice for insulation. XPS is slightly cheaper than polyiso and is also much easier to find. Like polyiso, it does not retain water so you shouldn’t have to worry about mold issues if the walls are sealed correctly. Many van dwellers successfully insulate with XPS and it is one of the most popular options for insulation.

Expanded polystyrene (EPS) – White Foam

Expanded polystyrene is an open-cell foam board. It has an R-value of R-4. It is the cheapest material of the foam boards. However because of the open cells, moisture can build up within the spaces. For this reason the material is not recommended for insulating your van.

How to attach foam boards to the walls

Foam board is lightweight and can be easily attached to the walls. Just like the flooring, foam board can be cut to size using cardboard templates and pressed into place. ¾ – 1 inch of insulation is a common wall thickness to use.

High strength adhesives such as 3M high strength 90 or gorilla tape are great ways to hold the foam in place. However, if you want to make sure the walls are really sealed for moisture, you’ll want to use a spray foam to adhere the boards to the wall.

Great Stuff gaps and cracks spray foam can be used to glue the foam board to the walls (or ceiling). This is an excellent way to seal off gaps as you install. Great stuff spray foam can also be used to cover any small oddly shaped areas of your vehicle. If you want to see a step-by-step guide with pictures of how to apply foam board, this article by GNomad Home and this article by the ProMaster Forum are great resources to use.

Spray Foam Insulation

Yellow Spray Foam

Yellow spray foam has an excellent R-value of 6.5. It is resistant to water so you will have no moisture buildup and it will not mold. Yellow spray foam can be very expensive. You’ll be looking at a few hundred dollars if you choose this method. Yellow spray foam comes in cans and can be very complex to install yourself. If the process is done incorrectly, your walls will not be flush. It can also be difficult to mask many areas of the vehicle so you have to be very careful about how and where you spray. Many people choose to have yellow spray foam professionally installed. If this is something you want to do on your own, this article by the ProMaster forum has an extensive description on how to do so. Yellow spray foam can be one of the best ways to insulate your van if you have the patience and money.

Fiberglass Insulation

Fiberglass insulation is very popular when insulating homes, and many van dwellers use this type of insulation as well. Its benefits include being very easy to install, easy to find, and cheap to use. On the other hand, fiberglass insulation does absorb moisture. If you choose to install fiberglass, it will be extremely important to seal up the walls afterward so you can be assured no moisture or molding will occur inside. Fiberglass has an R-value between 3-4 depending on the type installed. The fiberglass material can be a skin and lung irritant during the installation process and beyond. Because of this, it is especially important to take proper precautions during the install and seal everything correctly. Overtime, the fiberglass insulation may become droopy or distorted due to vibrations of the vehicle.

Due to the pros and cons of fiberglass insulation, this material would not be at the top of everyone’s list for install. That being said, when installed professionally and sealed correctly it will do a good job of insulating. This material may be perfect for filling in any nooks or cranny’s in the doors or framing. Fiberglass does lose some of its insulation value when compressed so be careful to not pack it too tightly.

Thinsulate Insulation

Thinsulate is a product developed by 3M and is similar to fiberglass insulation. It is made up of polyester and olefin. Unlike fiberglass insulation, these materials are non-toxic; so it is ok to install without protective clothing. Thinsulate works as both a thermal barrier to block conductive heat and sound barrier. Although the material itself does not absorb moisture, it is not a water-barrier; meaning moisture can still get inside of it.

Thinsulate has an R-value of approximately R-3. This material is difficult to find in stores, so you will probably have to purchase it from the 3M website. If you choose to install with Thinsulate you’ll be paying on the higher end of the scale when it comes to insulation. However, this will come with the benefits of easy removal, non-toxic particles and a sound-resistant barrier. If you’d like to see a full install of Thinsulate, check out this step-by-step guide on how to do so.

Insulating the Ceiling

The ceiling can be insulated in the same way as the walls. Ridged foam panels and yellow spray foam are both great choices. Because hot air rises, convective heat loss is going to be one of the biggest problems to mitigate against. This means you will want the thickest insulation on your ceiling (assuming you are willing to give up a little headspace). Anywhere from 1-2½ inches of insulation is a good number to shoot for.

The ceiling can get a bit tricky if you want to install lights or a vent fan for heat escape. Make sure to plan all of the wiring and accessories out before you attempt to tackle the roof. Some vanlifers like to hang decorative wood panels overhead. Keep in mind, those will not attach well to foam so you will need to add in studs or leave extra space for building off of if this is the case. If you would like to see a step-by-step guide of how one couple insulated their ceiling, check out this article by GNomad Home.

Insulating Windows

The final step is insulating the windows. Windows are a major source of radiant heat transfer. When placing a reflective surface on a window facing out, heat from the sun will hit it, and bounce back out keeping the van cooler.

If you place a reflective surface on the windows facing in, you get the opposite effect. When running a heater like a portable propane furnace, that heat generated will hit the reflective surface and bounce back into the van rather than going straight out of the window. This keeps the inside temperature more constant.

InfraStop

Infrastop is a double-bubble reflective foil much like Reflectix. This can be bought in rolls and easily cut with scissors. It has an R-value of up to R-6. Infrastop can be taped to the windows and is reflective on both sides. It is also a vapor barrier so you won’t have to worry about it holding in moisture. 

Reflectix

Despite there being more efficient materials, Reflectix is still a popular insulator for windows, and rightfully so. Reflectix when used correctly, rates in at an R-3. On windows, Reflectix is a light and easy material to work with. It can be cut with a regular pair of scissors and stuck on with tape. When sticking Reflectix to windows, the air gap will be the inside of your van! There is a lot of space here for reflection to occur.

Insulated window curtains

There are a number of different reflective curtains available online. Insul-shine is reversible and can be flipped to either trap heat inside or bounce sunlight back outside. This fabric can be bought in rolls and stitched to the shape of your window. Finding a way to hang these curtains may become a challenge. Depending on the material of your door frame, you may be able to use clips, hooks or Velcro.

Windshield cover

The windshield is probably the largest window in your vehicle. Possibly, the easiest way to deal with such a large area is to purchase a reflective sunshade. Most of the sunshades online are going to be relatively similar. One important thing to keep in mind is the two best materials to block radiant heat are: gold and aluminum. Because of this, you will want to make sure you are purchasing a sunshade with an aluminum coating like this one. Thick, aluminum-coated sunshades are also going to be the best choice available for the warmer months when you want to keep you car cool.

Filling in Odd Shapes in the Van

Every van has little nooks, crannies or cracks that don’t quite fit in with the standard insulation instructions. Great Stuff gaps and cracks spray foam is an easy way to fill the gaps. Door panels or framing might have large open spaces. Do your best to stuff these areas with any scrap foam you have laying around. These spots might be a good place to add in fiber insulation, just remember not to compress it to tightly. Seal everything up with spray foam or tape so moisture will not get inside. At this point you’re almost done!

Closing everything up

Chances are, you probably aren’t going to sit around in a foam box. The next step will be figuring out what material you want to use to cover the walls. We’re going to save this topic for a different article.

Final thoughts on Van Insulation

Insulating your vehicle is less exciting of a process, but worth the energy in your build. You really get to exercise your research and construction skills here. Proper insulation is a delicate balance between R-value, price and space constraints. It is very rewarding and you’ll be happy you took the time to do so when winter rolls around. Combine this information with our post on how to heat your van, and you’ll be well on your way to a warm and cozy winter.

We’d love to hear how you chose to insulate your van and update the article with any additional information we can find on the subject. Show us your insulation process and we’ll share it on social!

Resources

Insulation is a complex topic and there are many great resources on the web to learn from. These are some of our favorites:
Cheap RV Living
Build A Green RV
ProMaster Forum
GNomad Home

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