Goose down is the best insulator. It's the warmest by weight, most packable and it also feels the nicest to wear. Individual feathers conform to the body's curves and fold better than any synthetic ever has. That's why goose down is frequently used in clothing and sleeping bags.
But there's a caveat (of course). Get down wet with sweat, precipitation, or by dunking it in the nearest water source, and it loses its ability to keep you warm. So if you're climbing an 8000-meter peak or backpacking over a spring weekend, down isn't always the best choice. Synthetic insulation, on the other hand, keeps you warm when wet, but it can be stiffer and doesn't have the same warmth-to-weight ratio. The North Face has been field-testing a new type of synthetic insulation that it claims will have the best warmth-to-weight ratio on the market. The secret? Fuzzy balls.
The company recently introduced a new insulation, ThermoBall. It's a polyester insulation, like most of the other synthetic insulations out there, but instead of being laid out in long strands inside your jacket it is chopped into short strands and then frizzed and frayed into what look like miniature cotton balls on a bad hair day. The frizzy part of the balls sticks to other balls, and forms a heat trapping web. The balls are as light and as packable as down—only without the quills that can poke through your jacket's outer fabric. By weight, ThermoBall is 15% warmer than the warmest synthetic insulation available, according to The North Face. It's still not quite as warm as down, but it's new. So in a year, it could be.
The North Face is introducing ThermoBall insulation in its ThermoBall Jacket, tested by Jimmy Chin, Conrad Anker, and Renan Ozturk on their recent ascent of Meru. The jacket has small, triangular baffles, which keeps the ThermoBall lofted and prevent cold spots. As the insulation migrates downward with gravity—alternating triangular points force the tiny ThermoBalls to ride high in the triangular shaped baffle. A pre-cinched hood, cuffs, and bottom keep warmth in, reinforced shoulders keep your pack from wearing it out, and large zip handwarmer pockets keep your fingers toasty when your gloves are off. Available July 2012, $280, thenorthface.com.