I often get into it regarding insulation in a van. Often times it is with people who have never lived in a van and are just parroting what they have heard. I started that way as well. I repeated what others have heard but at the time I was open to those who are actually doing it. It was then I started to notice a trend.

Those who want a minimalist build, and are low on resources (this is where I started) are less likely to need, or even benefit from insulation in the summer.

There are two main situations that I know of from first hand experiences that reinforce the point for me.

The first is being up in the North Western area of the United States during summer months.

It is hot and dry during the day, but cool or cold at night. During the day with or without insulation the best you can accomplish is to match the interior and exterior temperatures. If you have an insulated van there won’t be any hotspots, but unless you are running AC you have at best the same result as I do without any insulation. Its going to match the exterior temperature.

The hotspots I speak of are a hot section of my van. Depending on how I’ve parked I can choose which side this will be. I typically choose the back door. This creates an area that will be warmer, but it is closest to the exhaust fan. Short of using the potty I will never feel it.

The next option is the front window. While this will bring in a bit of heat it is really only going to be slightly different then the back. I’m still limiting my cross section to the sun and thus the heat I’ll absorb.

The other option is the passenger side wall. This is okay for me because I’m not next to it, but it isn’t ideal as it is such a great cross section. I also need to avoid direct sunlight on my skin. I need to put on long sleeves/pants or keep the side door closed.

The worst section is the driver side wall. This is worse for me because I’m near the wall when I’m working in my van. My bed is also right there. As bad as it is, it isn’t that bad. The wall will get hot, very hot in fact. The thing is, with ventilation the heat doesn’t really extend far in the vans interior.

How does the North West compare to the South East such as Florida, where it is not only hot but humid?

Well, I’ve spent a great deal of time in Florida too. I’ve also talked to insulated van people in the wild. They generally have the same issues as me, with two exception. They don’t seem to pay attention to the vans orientation to the sun, and after a long drive my floor gets warm. Theirs won’t transfer the heat into their van so it isn’t something they bring up.

When I’m driving it stays cool due to air flow. When I’m parked it flows up through the van interior. There is no “cooler” place.

The ventilation takes care of the majority of it, after it has passed through your body making you feel warmer. The heat won’t build up in the van though. Eventually the under side cools down and all is right again This can take 20-40 minutes. I’m very tempted to install floors (maybe not insulated) to mitigate this and give me a flat even floor.

Every other issue with it being hot during the day and once it gets hot it stays hot until it cools down outside is basically the same. The only advantage they have are in those situations. Many have reported they can stay in the van later into the morning/early afternoon before it gets too warm to sleep. After comparing times though it seems as though that is about the same time for both of us. At most they get another 30-60 minutes.

But insulation is cheap and only takes a bit time to install, why not?

If you take everything I’ve said thus far you may be thinking to yourself, well there are only a few advantages but those might be worth it to me. I’d rather install it and not need it then need it and not install it. I get that, I really do.

My problem with insulation is it slows down heat transfer. How is that a problem? Well funny you should mention that. At night in my van my walls ALWAYS FEEL COLD TO ME, especially in Florida. Tonight when I go to bed, my walls will feel cold to me. If I had insulation the heat would be trapped in here with me. Without insulation I’m bleeding heat through every metal surface.

Thermal Load, Mass, and your van.

During the day when there is a huge thermal load you will be absorbing thermal energy. That is basically any source of heat. Heat such as the sunbaked concrete you are on top of, the sun itself, the motor/drive train, etc. The Thermal Mass of the van will start shifting from cooler temperatures at night to warmer temperatures during the day. Absorbing all of those sources of heat.

Think about this: The effect of both the thermal load and thermal mass is why the air conditioner of a car is SO huge. The window AC in my non-insulated van is 5000 BTU. It works fine, if it has been running for awhile. I don't know the exact specs for the motor driven AC, but I've seen estimates as low as 16,000BTU to over 20,000BTU. At a minimum that is 3 times more. 

How often do you run your AC at full blast when you get in a hot car in the summer? How long until you turn it off or down? How long does a car parked stay warm even after then sun has set?

It takes time for a car to cool down in a parking lot from the heat of the day because of the thermal mass it has and the thermal energy it needs to expend. During the day, it kept absorbing it. At night, the better the insulation the longer it will take for it to cool down.

The very same thing happens in our vans. The ventilation saves us from the worst of it. The problem is we are also heaters ourselves! If you get in the van early afternoon, and the van is insulated it is very possible that you are adding to the interior about as much as it is expelling. Thankfully, ventilation will help remove some of your body heat.

The walls of my van feeling cold to me are a sign that there is more heat inside then there is outside.

By forcing heat to only go through the air (which is a poor conductor of heat) to leave by ventilation and keeping the interior insulated I’m making it difficult for heat to escape during the time when it is most important to me. The time I’m most likely to be inside my van. It is the time when I have the least amount of options or alternatives to choose from.

During the day, I don’t have to be inside during particularly warm days. I can be outside enjoying the full breeze sitting on a picnic table doing my work, or reading a book. I can enjoy the shade from a tree or go for a walk. Not letting my body heat contribute to the thermal load problem I know I’ll be

So in short, insulation will only slow down heat transfer, not stop it. It is only effective where it is installed. Gaps and other things can mean that you are not really benefiting from insulation.

How effective is it?

I don’t know how effective insulation is in the real world setting, because there are many different variables. I can tell you it is quite effective at trapping heat, and my ventilation didn’t stop it.

I used this left over Reflectix to create a “thermal break” In other-words, a partition to help keep the heat in the front from going to the back — or vise versa. Depending on where and how I’m parked it is possible my AC will cycle on and off during the day!

I take naps at work during my lunch break. Where I park to get sun for my panels, my front window is facing the sun. I can choose a shaded spot or a sunny spot with the sun in my windshield. I don’t have any other options. Even before I had the AC I tried this. I noticed that with just my rear-only ventilation and my front windows cracked that the exterior part of my van was about the same or a bit cooler then normal. The most amazing part is it didn’t really get warmer from the sun. I thought this was great and left them up! Not only could I make it dark in the back during the day for my nap, but it was a clear night and day difference. Heat was building up in the front, but not in the back. You could feel hot air going from the front to the back as the exhaust van pulled fresh air in, but that wasn’t that bad and there are some more vents in the back as well.

After several months of having this up I started noticing Athena having issues with how hot it was at night. The van took several hours to cool down instead of maybe an hour. I thought to myself it was just the heat etc. One particularly hot and humid night she sat up front against my wishes. In doing so she tore down one of the panels and as I was setting it back up I noticed the van had cooled down pretty quickly.

Being stupid, I didn’t notice the trend. Later that night it got warm again, but I didn’t think of it much at the time.

One more time she was having trouble sleeping due to how hot and humid it was and I removed the barrier to start the motor for the car AC for her. After dropping it I noticed how cold it was outside. It felt very cold to me. Shortly after removing the reflectix it cooled down enough and she was comfortably asleep.

Athena sleeping in the van.

I hadn’t even started the car. I had just finished moving enough things around to store the reflectix. With that I knew, how powerful insulation can be.

The key things to take away.

  • Insulation will only slow down heat transfer, not stop it. The van will still get hot during those hot summer days no matter what.
  • Sometimes you want the heat transfer to go slow and appreciate the result. This will most often be during the day in the summer, and the night during the winter.
  • Sometimes you don’t want the heat transfer to go slow! This will be during the day in the winter, and at night in the summer.

If you are going to be spending most of your time in the van during the hot summer days, insulation will help. If you are going to be spending most of it at night, insulation will make it take longer to cool down. No matter what! Whats worse, while you are inside the van it will ALWAYS be warmer then outside. At the very least you are a source of heat! This is true with or without insulation!

The only way I’m aware of to ALWAYS get the good result from insulation is to have enough power to forcefully climate control the van. Future vandwellers that are getting started with minimalist or budget builds won’t be able to do this.

Am I anti-insulation?

While it may sound like I’m anti-insulation, I’m not. There is a time and a place. It does a good job if you install it properly and understand the negative side of it as well. My next build will have all around foam insulation. It will also have an AC unit capable of running on battery alone for several hours. That isn’t a budget friendly solution.

My only opposition is the belief that insulation is required. I think, given what I’ve experienced and what I’ve heard that it is counterproductive for budget-friendly builds if the proposed benefit is that of keeping the interior cooler. For me, I’m less concerned about the day time temperatures as I am about the night time temperatures. I live out of my van, not in it.

This Post Has 2 Comments

  1. I like your thinking and the way you express it. I went a different way for a different use case. I picked up used XPS off CL for very cheap. 1″ for the walls, 2″ for the ceiling.

    The skin of my (white) van in sunlight is significantly hotter than ambient; re-radiating heat into the van was a real thing for me. At the moment the van’s exterior is 33F hotter than ambient. That might actually be a good thing, since it’s a bit chilly for me at 57F. I am in town for an appointment and can’t follow the warmer weather at the moment.

    I’m dependant on solar charging and must park in the sun. Solar panels run something like 60F over ambient; even with an airgap it’s typically hotter in the shade under my panels than in direct sunlight. Even with 2″ of XPS it’s 2F warmer inside the van under the panels than in sunlight.

    As far as retaining heat inside when I want it cool, a roof vent with thermostat handles that nicely and automagically (although more expensively than I’d like to admit).

    Keep up the good work, brother. I’ll be following along.

    1. Thanks for stopping by! I’ll take a look at your blog when I have some more time as well.
      I’m torn between keeping up with my blog and starting a youtube channel. I seem to fail at doing both as I had originally intended.

      Now that I’ve got AC, I do plan on getting insulation. It simply isn’t worth it in this current van. That is why I’m upgrading 🙂

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