Insulation against the heat!


Hello fellow vanlifers,
I am about to kickstart my build in the back of my 2009 Mitsubishi express and I live in south Australia (its bloody hot) after doing some road trips in my baby last year I knew I needed to insulate before venturing out again. Does anyone have any tips for what materials they would recommend for insulating against heat? Ideally I’d like it to be budget friendly but effective.


Hi Bronte

I used earthwool and foilboard from bunnings for insulation in my build, I’ve got a 2009 express as well :slight_smile: Shove as much of the earthwool as you can in the walls so its packed nice and tight. The foilboard is useful because you can cut it to exact shape, I only needed 2 sheets and I did the walls floor and roof with it - it’s a tight fit to get the roof panel back on but it can be done.
Both cheap options and seem to do the trick in tandem, I live in Qld and it is enough to take the edge off so its not an absolute oven! Let me know if you have any more questions.

Good luck with the build!



When it comes to heat, the most effective solution is also the cheapest, simply park in the shade. A thin sheet of plywood running full length, mounted to a roof rack (gutter racks preferably) can keep your roof shaded. Positioning your van so your back window is facing the sun also helps a lot, and blocking the sun from entering it.

Ventilation works far better than insulation in combating heat. Heat rises, crack your front windows, and have high vents in the back. Add low vents, and convection will move the heat up and out without the need of a fan or any power. Make sure all vents are screened to keep bugs and rodents out. Cover your windows on the sunny side.

Insulation in vehicles is terribly over rated, but covering all exposed metal, to create a thermal break between the metal and the interior, can help tremendously.

If you’re going to be inside the vehicle in hot weather, you will likely need some form of air conditioning. Compressor driven air conditioning is going to require either shore power or a generator, but 12 volt swamp coolers can be built that use very little power, and are just as effective if not more effective. Different variations can be used, to make them very effective regardless of humidity levels. Mine only uses 1.5 amps on low, and 2.5 amps on high. A friend built his to be USB powered, so his uses even less power.

I also love my 12v heating/cooling blankets and seat cushions. They also use very little power, and are very effective. When outdoors, they have heating/cooling clothes, as well as cooling neck/wrist/ankle wraps, and vests and things available too. Staying warm or cool, either inside or outside, is easy enough with the right equipment, and it can all be accomplished without insulating your vehicle.

Insulate your vehicle for sound deadening, not temperature control. Temperature control is better handled by more effective methods. Staying comfortable is actually cheap and easy with the right equipment and designs, regardless of what the temperature is. Nobody NEEDS insulation, air conditioning, or even power to stay comfortable, history and intelligence are the best tools in our arsenal. Shade, ventilation, water, and evaporative cooling have yet to be topped by any more modern inventions. Their only accomplishment is getting people to pay more for similar or worse results. Gypsy caravans had non electric fans and evaporative coolers. The wealthy from the world over, and for centuries before electricity, knew how to stay both warm and cool. Those techniques and devices will work equally as well today as they did a hundred or thousands of years ago.


"Too hot? Seek shade and ventilation, not insulation.
Still too hot? 12v SWAMP COOLERS WORK!" ~ Happy Camper


Good for you… but for sure staying cool will be your number one priority in that south oz heat. :exploding_head:

Other ideas already mentioned are correct for sure.
Shade is key on top of the vehicle and a good awning to shade while you keep the largest opening (the slider in your express) open as often/long as you can.
An electric fan/vent (or two) blowing out in the roof is a huge help, but don’t fall into the trap many do of putting two in the roof and blowing one in and one out as you’re just pulling in more hot air. Best case scenario put intake vents in the floor so you’re pulling the cooler shaded air into the van and circulating up bast the bed before going out the roof (if you’ll have a fridge, this is also a good way to keep it as cool as possible, which also mean more efficient/less power draw).

BUT- don’t discount insulation. Its huge and the only way you’ll live comfortably through the summers. Highly, highly recommend 3M Thinsulate. Super easy to work with (can cut it with scissors), can be stuffed into every nook and cranny (including roof ribs) and has both thermal insulation and sound deadening qualities. Most importantly… its hydrophobic and mold/mildew resistant, which is good for the van and good for your lungs!

Something like this…hopefully available in AUS
Thinsulate Van Build Insulation