It can be difficult and even dangerous trying to live out of a vehicle in cold climates. However, with proper van insulation and heat management you can be comfortable in sub-freezing temperatures. Insulation keeps heat in your vehicle and is complimented by our tips on how to heat your van in winter.
The Three Types Of Heat Transfer
If you want to keep your DIY camper as warm as possible throughout the winter, you will want to address all three types of heat transfer: radiation, conduction and convection.
If you are unfamiliar with these terms, read our post on the three types of heat transfer.
When building out your van, you want to resist heat conduction by insulating the 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 can 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, proper van insulation becomes a delicate balance between R-value, space, and expenses.
R-value is measured per inch. This means 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:
|R-value per inch
|Thickness for R-6
|Extruded polystyrene (XPS)
|Expanded polystyrene (EPS)
|Yellow Spray Foam
|Reflectix (no air-gap)
Many insulation values referenced here came from BuildAGreenRV.com
Dealing With 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 moisture that builds up on the inside of windows when sitting in cold weather.
There is an ongoing debate among vandwellers on whether it makes sense to seal off 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.
Adding A Vapor Barrier
The idea of a vapor barrier is to seal off the interior of the van and protect the walls and insulation from being exposed to any of the moisture that develops inside the van. In a perfect world, no moisture would reach these spots and they’d be a dry desert free from mold and rust.
The problem with adding a vapor-barrier in a vehicle is that it’s difficult to install practically. If there are any slits or gaps in the material, moisture can get behind the barrier and build up between the watertight surface and the wall.
And in a vehicle, there are a lot of little areas and spots that can rub where moisture can enter. The entire body is full of holes for things like lights, trim pieces, wires, and manufacturing seams.
The whole vehicle flexes around, you will be driving through the rain where your wheels can spray water from the underside. Vans have to serve more purposes than houses, so trying to add barriers can catch up with you.
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 to see it or treat it.
With this in mind, the alternative to trying to seal off with a moisture barrier to insulate with materials that don’t retain water and make sure you have good airflow to make sure there are no stagnant spots for sitting water.
Proper ventilation is key to reducing condensation.
Its still beneficial to seal off as much moisture coming in from the outside as possible, but it’s best to go in with the mindset that the interior will be exposed to moisture in some form or another.
- Read our post on avoiding condensation and moisture buildup in your van
Before You Insulate Your Campervan Conversion
Before beginning the van 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.
- If you’re going to add soundproofing, do that first! Read our guide on soundproofing your campervan
Getting Started With Van Insulation
Now that we’ve got the technicalities out of the way here comes the good stuff. What material should you use to insulate your van? The five main areas of focus are:
- 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. We recommend Extruded polystyrene (XPS) for the floor. Or just go with straight plywood and skip insulating this area entirely.
XPS has an R-value of R-5. It is a dense material that would take a lot of weight to compress. Because of this, it makes the perfect material to build on top of. ½ inch of material is about 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.
Insulating The Wheel Wells Of A Campervan Conversion
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 your walls with yellow spray foam this would also be the perfect material to use on the wheel wells.
You will get a lot of return on investment by insulating the walls of a campervan build. Material choice is going to depend a lot on personal preference.
Some vans are more 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.
A Note On Reflectix
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. We talk more about Reflectix in our post about insulating for hot weather.
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. As far as rigid foam panels go, 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 (and less expensive) 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 expanded polystyrene is not recommended for insulating your van.
How To Attach Foam Panel Insulation 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 a box cutter. Cardboard templates are a great way to estimate sizing. Then just press it 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 the ProMaster Forum is a great resource to use (insulation starts at post #8).
Spray Foam Insulation In A Campervan Conversion
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 expensive.
You’ll be looking at several hundred dollars if you choose this method. Yellow spray foam comes in cans and can be 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 careful about how and where you spray.
Also note that it is a much more permanent solution. Once installed, it’s an extensive and messy process to scrape it all off if you need to address problems behind it.
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 is popular when insulating homes, and many van dwellers use this type of insulation as well. Its benefits include being 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 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 fine 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. It requires ventilation to dry out, similar to a jacket or sleeping bag (which, coincidentally, Thinsulate is used in as well).
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.
Some van lifers 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.
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 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 is a popular and effective insulator for windows. When used correctly, rates 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.
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.
The Bottom Line
Foam insulation is one of the most popular types of insulation. It’s easy to install, relatively inexpensive, and provides a good level of insulation. However, foam insulation can be flammable, so it’s important to use a fireproofing spray if you’re going to use this type of insulation.
Another popular option is fiberglass insulation. Fiberglass insulation is non-flammable, but it can be more difficult to install than foam insulation. It’s also more expensive than foam insulation, but it provides better thermal protection.
If you’re looking for an environmentally friendly option, there are also several types of natural insulation available. Sheep’s wool and cork are two popular choices. Both of these materials provide good thermal protection and are environmentally friendly. However, they can be more expensive than some of the other main types.
Whichever type of insulation you choose, be sure to add a vapor barrier to prevent moisture from condensing inside your van. For even more comfort and energy efficiency, consider also installing insulated blinds or curtains for the windows.
Things To Bear In Mind
Things to Bear in Mind
When it comes to insulating a campervan, there are a few key things you need to take into consideration in order to ensure a comfortable and energy-efficient space. First, consider the climate you’ll be spending most of your time in.
If you’re planning on spending extended periods of time in cold weather, don’t underestimate the importance of completing this step to a very high standard. If your van is not properly insulated, you could end up freezing at night, and it could turn an otherwise great journey into a perilous one.
On the other hand, if you’re mostly going to be camping in warmer climates, insulation will still be important but not as crucial.
The quality of the installation is also key when it comes to insulation. You really need to make sure everything is properly sealed and installed so that heat doesn’t escape and cold air doesn’t seep in. This will help you keep your van comfortable no matter what the temperature is outside.
We learned the importance of this point the hard way by enduring quite a few nights that were a lot colder than we had expected. If installing your insulation is not something you’re that confident with, it could be a very wise investment to have a trusted professional carry out the work. It will probably save you money in the long run by helping to avoid the need to replace or redo any of the work.
It’s also important to remember that when you’re living in a van, every ounce counts. So you should definitely consider the weight of your insulation when you’re planning your build. The heavier the insulation, the more weight your van will have to carry. This can impact your gas mileage and make your van harder to handle on the road.
Fiberglass insulation is lightweight and easy to work with, but it doesn’t have the best R-value (the measure of an insulation’s ability to resist heat flow). Spray foam is much heavier than fiberglass, but it has a much higher R-value, so it’s a good choice if you’re looking for maximum insulation.
Rigid foam is somewhere in between fiberglass and spray foam in terms of weight, and it also has a good R-value.
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 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.
Insulation is a complex topic and there are many great resources on the web to learn from. These are some of our favorites: