“You get the warmth of a much thicker baselayer from a thin fabric that isn’t overly hot or bulky,” says one tester who wore the top for 15 days on the San Juan River. The trick? Columbia’s Omni-Heat technology: The interior of the fabric is covered in aluminum minidots that reflect warmth back to your body, much like a space blanket. (The dots are dispersed so that 70 percent of the coverage area is breathable—which makes the shirt much more air-permeable than an actual space blanket.) Large swaths under the underarms are left dot-free to increase wicking and breathability.
“For my four-day hiking and camping trip in Yosemite, I packed a single shirt to do double duty as sun protection and an extra layer,” says another tester. “On the long slog up Yosemite Falls in temperatures pushing 90°F, the wicking, venting (thanks to a generous 10-inch zipper), and dry times were above average.
Under a shell, the shirt was plenty warm to thwart 40°F temps and 15-mph winds on the summit of Mt. Bachelor. The polyester fabric is creamy smooth, and, after 36 test days and a dozen washings, it still looks new. Bonus: The stretchy fabric hugs the body without looking like a contour map. We also like the price.