When you drive a Vanagon, you learn all kinds of simple, passive solutions to the indignities of vanlife. Take air conditioning, for example. Mine had it, but it was prone to failure. One time, coming across the Mojave while driving back to California from Zion, we got stuck in stop-and-go-traffic for more than 20 miles with the temperature throbbing between 113 and 115. My companion and I bought a 10-pound bag of ice and filled baggies, which we put on top of our heads.

I also made liberal use of Reflectix, the doubled-sided insulation, which is a staple of vanlifers everywhere. It’s cheap, light, and remarkably effective at bouncing the sun’s rays skyward and body heat back to you— sometimes it seems there’s more Reflectix in Sprinters than sheet metal.

If you don’t know about Reflectix, read on. If you do, read on anyway so I can tell you how I tweaked the common usage in a way that I think’s pretty cool.

With the van, I pulled out all the cabinetry, carpeting, and headliner and filled the spaces with sound deadening materials and a bit of Reflectix. Then I made window insulators out of Reflectix. For my first effort, I used newspaper to make a pattern, but it turned out to be easier to press the Reflectix against the window, Sharpie the outline, and trim away with scissors until the fit was right.

The problem was that a Vanagon’s windows are flat, with no lip on the molding to hold them in place. Suction cups like you see on commercial insulating blankets don’t work well when it’s really cold, and tape wasn’t really an option. I opted for what seemed a clever fix—I hot-glued super magnets inside the Reflectix. They pulled toward the steel walls, and bam! It worked perfectly.

Then I sold the van. If you’ve ever had a Vanagon, or a boat, or cabin, or a two-stroke anything, you’ll know why. Best of times, worst of times, etc. So, I went back to my first generation Sequoia, 14 years old and still running strong, and incorporated the best elements of vanlife. The first thing I did was make new window insulators.

The Toyota’s windows have lips, so they stay in place without magnets, which are absurdly expensive. After the experience in the van, it went fast and smoothly (making them slightly bigger than you think they need to be seems to help hold them more securely in place—as you can see, I need to redo this one). But because it’s not as easy to stealth camp in an SUV as a van, I also had the idea to increase the privacy by covering one side of the Reflectix in black gaffer’s tape. And, whoa, does it work well.

Here’s how I use it: When it’s cold, I place the insulators with the silver facing inward and the black facing outward. This bounces heat back toward the interior while making it nearly impossible for anyone to see what’s happening inside (with tinted windows…clear windows, you can see the tape). If the sun’s out and hitting the black gaffer tape, it also has the effect of warming the vehicle from the outside, too. In my solo tests, it makes the interior 10 to 15 degrees warmer; with two bodies, the effect is greater.

Conversely, when it’s hot, I now have a full set of window reflectors turning back solar radiation at every window, which makes a dramatic difference in cooler or fridge performance, as well as providing a little piece of mind for leaving laptops and other electronics inside on a sunny day.

Making the insulators is simple—you don’t need an Instructables step-by-step, that’s for sure. A roll of Reflectix is less than 30 bucks at Home Depot or Lowe’s and can cover two medium SUVs no problem. Gaffer’s tape is easiest to find online—get the two-inch width to make the process go faster.