Like a lot of outdoorsy people, I’ve spent years trying to perfect my body temperature on sweaty adventures when the temperatures are low. It’s easy to think that when it’s cold out, you want an insulated jacket such as a down jacket or a fleece, and when it’s warm out, you lose the insulation altogether and hike in a T-shirt. But of course, if you’ve ever left the house, you know it’s not that simple.
There are actually loads of scenarios where you might need some insulation but traditional insulation, like down or fleece, would make you far too warm. In cold weather, you often need some insulation, but if you head out on a high intensity pursuit like trail running or ski touring in a down jacket, you’ll soon be dripping with sweat. Long summer adventures like hiking a 14er on a warm day can often be bookended by cold mornings and evenings. Gaining elevation can mean that even though you didn’t need insulation at the trailhead, you find you do need it for that windy summit or exposed ridge. And of course, even in the best weather, when you’re adventuring in the backcountry there’s the possibility you could get lost or injured, spend the night on a mountain, and need more than your trail running shirt for warmth.
