It always seems that whenever a heat wave sets in, I find myself atop an asphalt roof or inside an attic. Luckily, the last time the mercury approached triple digits, I had an Isotherm Cool Vest at my disposal.

Made from flame-retardant cotton, this product has polyester sleeves inside the front and back into which two large cooling packs are inserted and secured with Velcro. The standard model comes in Walmart blue but is also available in a bright yellow version that meets ANSI/ISEA Class 2 High-Visibility requirements.

Sizes range from small to extra large. The one I used was M/L, but Velcro adjustments at six different points led me to believe that it could be made to fit almost anyone.

Isotherm’s cool vest is equipped with controlled-release phase-change cooling packs (not ice or gel packs) that are designed to maintain a consistent 55°F temperature for as long as four hours.

According to the manufacturer’s instructions, the cooling packs can be energized before use by placing them flat in a freezer or refrigerator for a few hours, or by immersing them in ice water for 20 minutes. They’re ready to get to work when the clear liquid in each compartment has congealed into a white solid.

Although I feared that the experience of putting on the vest would be like taking the ice bucket challenge, what I felt was more of a cool breeze than an icy blast. Bullard, the manufacturer, explains that its cooling-pack inserts feature a phase-change technology that maintains a consistent 55°F for up to four hours, depending on the job conditions. I was working in a sweltering attic when I put it to the test, and it was easily two hours before I noticed sweat dripping down the back of my neck.

When the packs lose their cool, submerge them in ice water for 20 minutes, and they’re ready to get back to work.

The first time I tested the manufacturer’s claim that an exhausted pack is fully revived after only 20 minutes in ice water, I nonchalantly tossed both of them in the cooler. When the timer went off, I discovered that the fully submerged pack was solid, but the one I’d left floating on top was semi-liquid. If you’re planning to take advantage of a lunch break to recharge these batteries, pour extra ice over the top, or weigh them down.

When I had to put on a toolbelt, I was relieved to find that the vest did not get in the way. The six-pound weight of the garment was not a bother, but the bulkiness was. When the cooling packs were fully charged, they were as stiff as concrete. But within a half hour, they softened up to become more flexible and form fitting. Compared with being hot, miserable, and unproductive, for hours, a few minutes of discomfort was a bargain.

Isotherm can be purchased online for about $220. Extra cooling packs are also available.

Photos by the author.