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Adding Van Insulation For Hot Weather

There is a difference between adding van insulation for hot weather, and adding van insulation for cold weather. When it comes to hot weather, radiant heat prevention, ventilation, and airflow are going to be some of the biggest areas of focus.

In this article, we will discuss heat prevention that can be addressed during the van construction process. For additional tips on how to stay cool while on the road, read our post on tips and tricks for staying cool during summer.

Protecting Windows From Radiant Heat Transfer

When it comes to preventing heat inside a vehicle, the first thing you need to know is the three types of heat transfer and how they work. In a van, direct sunlight through windows (radiant heat transfer) will warm up the car more quickly than any other process.

To reduce radiant heat it must be reflected. Materials like aluminum, Reflectix, or Infrastop are shiny and will bounce radiant energy off the surface back into the environment.

To prevent radiant heat:

  • Cover the windshield with a reflective sunshade
  • Cover passenger, side, or back windows with a reflective material

Reflective windshield covers can be bought online and will make a big difference in the amount of heat that enters the vehicle. For smaller side windows, purchase a roll of Reflectix, or Infrastop that can be cut to size and placed over the window when parked.

Van sitting in the sunCovering window with reflectix

Homemade window covers

Custom window covers can be created by using Reflectix on one side, carpeting or cloth on the other, and a little bit of insulation batting in-between. This design allows for the shiny side to be facing out in the summer, and the reverse effect during the winter (reflecting interior heat back in). Window covers can be held up using Velcro, snaps, buttons, ties or simple press-fit.

Insulating Van Walls for Hot Weather

When insulating the walls of a vehicle, it’s important to think about what types of environments you plan to spend the most time. A van that is insulated to stay warm during cold weather will also keep warm air in during hot weather. There are three approaches that can be used for hot weather: high van insulation, low insulation and insulating with radiant barriers.

High amount of insulation + air conditioning

If you have the ability to power an air conditioner through a generator, shore power, or large solar array, then it is beneficial to have a large amount of insulation to hold that cold air in.

Little or No van insulation

If you do not have a way to actively cool the interior throughout the day, your van is going to get hot. Insulated walls will hold heat inside and make it harder to cool off. This is not ideal for hot weather. Many people find that it is more comfortable without insulation in hot weather because the van cools off quicker at night when they want to sleep. Keep in mind, without insulation the walls will be hot to the touch in the sun in this case.

Reducing heat with radiant barriers

Preface: This subject is under some contention in the vandwelling community. There is a bit of debate about how effective radiant barriers in walls actually are. We are continuously expanding our knowledge and will update this as needed.

Insulating walls with reflectixAs stated above, radiant barriers work by reflecting radiation back outwards. Materials such as Reflectix can be installed to reduce radiant heat transfer from hot walls of a van. As part of the installation, there must be an air gap for the radiant barrier to work.

Attaching a radiant barrier directly to a piece of metal such as a van wall, it would transfer heat (via conduction) through the radiant barrier making it significantly less effective.

Why can window covers be touching a window but still be effective? The reason is that in this case they are blocking a radiation spectrum that is not absorbed by the glass, so when it is reflected out it is “invisible” to the glass. Effectively the window is an air gap as large as the distance between the window cover and the sun.

Thermal Bridging

A radiant barrier must be supported somehow to maintain an air gap. Heat transfer through the support structure is known as thermal bridging. When installing any kind of insulation, it is important to reduce this; it is especially critical with radiant barriers.

If you were to glue Reflectix to metal ribs then the metal would quickly transfer heat where it touches the Reflectix. Even metal fasteners, such as screws in wood, can have an effect on heat transfer.

Try to reduce thermal bridging by using non-conductive materials, such as glue and foam to support the reflective side of your radiant barrier.Click To Tweet

This process of insulating with a radiant barrier takes a lot of construction, planning, and space. Reflectix and an air gap will not help much with the cold so you may need a layer of insulation inside the van as well. Keep in mind that while doing this you still need to mind moisture buildup and have the ability to install furniture inside.

Preventing the walls and ceiling from getting hot in the first place is a better method for most people. A white roof goes a long way.

Insulating the Floor

A surprisingly effective method of insulating your vehicle against the heat is by using proper floor insulation. Due to convection and radiation, hot air will transfer through the floor from the engine and exhaust during driving. This can also happen if you are parked above a hot surface like pavement.

The main goal is to insulate the floor well against conduction. This uses the same techniques and materials as you would for walls in the cold, such as foam with a high R-value. For more info on materials check out this article.

If you’re feeling ambitious and think you’ll be driving a lot, you can add heat shielding material on the floor of your van to reduce heat transfer from the exhaust and engine. More effectively, you can purchase heat shielding for your muffler and exhaust.

Advanced tip: an inexpensive laser pointing thermometer can be purchased to determine which areas of your van are transferring the most heat in. This can help you determine which spots need more insulation, or which areas of the vehicle require the most focus.

Vent fans and airflow

Van sitting in the sunCovering window with reflectix
📸@faroutride |

Appropriate airflow makes a big difference in the comfort of your van. To make airflow work at least two openings are recommended: one for air intake and one to pull air through. The further away you place these openings, the more airflow you will get throughout the vehicle.

An example of poor airflow would be having a vent fan in the cab (above the driver seat) paired with opening the driver’s window. Air will flow between the two but you will not get fresh air in the back of the vehicle.

If you have a vent fan in the cab area and open the back windows, you will get air moving through the majority of the van. To get the most airflow, consider opening different doors and windows throughout the day. Depending on where you reside, bugs may become a major factor in your ventilation flexibility. Options such as creating custom window screens or purchasing large bug nets for the side and back doors are necessary to stay comfortable.

For proper airflow:

  • Open doors and windows
  • Install a fixed vent fan in your vehicle

Read our post: best roof vent fans for van life

If you are concerned about installing a roof fan, smaller portable fans can be purchased that run off batteries, however they will not be as effective as a full roof fan.

Awnings and Roof Attachments

The roof of your van is going to absorb a lot of heat throughout the day. Placing white plywood or other reflective material above the roof will reduce the amount of heat that can get inside.

If you park in one place for extended periods of time, consider hanging an awning or tarp above your vehicle as a semi-permeant fixture. Being able to park your vehicle in the shade will make a big difference in the amount of heat that reaches the van. Even the shade cast from solar panels mounted an inch above your roof will help.

Attaching an awning to the roof-rack or side of your vehicle will give you a shaded area to hang out in the heat. We installed an awning so we could sit outside in the rain, but have found it to be much more useful in hot weather.

Additional tips

As van dwellers, we recommend following the weather for maximum comfort. If possible, head north during the summer, or to a higher altitude. Try to park in shade and face north if possible. This will give you the least amount of direct sunlight on your large windows.

Spend the day somewhere cold like shopping malls, libraries or museums. Limit activities inside the van such as cooking. Body heat will significantly increase the van’s temperature so try not to spend too much time inside.

It may sound counter-intuitive, but on hot nights it is often more comfortable to sleep outside. We spend a lot of our time on campground or BLM land and keep sleeping bags and a small backpacking tent in the van. We’ve found that sleeping in a tent is more comfortable in the summer than inside the van if caught in a heat wave.

For more tricks and tips read our post: tricks and tips to keep cool in the summer

Air conditioners, swamp coolers, and other active cooling

You may be asking why no one has ever installed an air conditioner in their van. The truth is, people have. It is possible to install an air conditioner, but it is not practical. An air conditioner takes an enormous amount of power to run. With shore power or a generator, it will not be much of a problem to install an air conditioner.

With solar power, you can run an air conditioner but it would need so many solar panels and batteries that it is not practical for most people. This van dweller was able to do it with 1000W of panels, 2000W inverter and 780 ah of battery. These things get pretty pricey and bulky, but for those building a sprinter it isn’t out of the picture.

Swamp coolers work by evaporating water with a fan that creates a cool airflow. Because of the evaporation process they do not work in humid environments. Additionally, they require a lot of power (to run the fan) and a lot of water (to evaporate). DIY swamp coolers that you see online do not work adequately in small spaces because of how quickly the air gets saturated with moisture and the lack of effective evaporation surface they are usually built with. For these reasons, it is easier to employ the other cooling techniques found in this article.

This Post Has 5 Comments
  1. I think the Reflectix debate can be cleared up a little bit if people remember that radiant heat is also known as infrared light.

  2. I disagree with the claim an Ac can not be run cheaply in a van.i have sportsman 2200 invertor generator that powers a 5000btu window Ac I have installed in back window. I can park at night and have the inside of the van in low 70s 1 gallon of gas gets me almost 12 hours cold breeze at night without any insulation. During the day with reflection in Windows and parking in shade with no insulation I can get 6 or 7hrs of cold Ac. I use about a gallon and half a day if I don’t go out after work at the most if its 90or hotter. I have been living in my 2001e350 super duty passenger van for 3 weeks and the last 3 weeks has been in 90s . I am considering putting reflection on top of roof for even more reflective power.

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