Down is the warmest insulation. In fact, when you’re hiking or skinning, it can be too warm. Same with Primaloft. It’s fantastic when you reach the summit, when you’re belaying your partner, or riding a lift, but get your heart rate up, and you’ll probably start to get sweaty.
That’s why Polartec invented Alpha.
Unlike down and existing synthetic insulation batting, Polartec Alpha is a highly stable layer of synthetic fibers that lets manufacturers use more open and breathable fabrics on the outer and inner layers of puffy garments. Classic puffies require down-proof fabrics inside and out so feathers don’t poke through, or they need high-density woven layers. Both create a vapor barrier, trapping moisture inside the garment during activity.
Polartec Alpha allows more air exchange in an insulating garment than ever before, for breathability and comfort when you’re generating heat. In addition to higher breathability than any other insulation because of the fabrics that manufacturers can use with it, Polartec Alpha stays warm when wet with faster dry times than other insulating layers. Highly compressible and feather light, it also provides some wind resistance.
Polartec Alpha was developed for U.S. Special Operations Forces (SOF). In testing by SOF, Alpha received the highest results of any Polartec product ever evaluated by the team.
"Polartec Alpha is a natural compliment to our existing layering system fabrics. It will function as outerwear or as an ideal mid layer. It packs small and can quickly recover from something as catastrophic as getting completely soaked while in the field,” said Allon Cohne, Polartec's director of marketing. "This is a never-let-you-down active warmth product that will replace other layers, lighten the load, and increase comfort in the field for outdoor enthusiasts."
It’s not as warm as garments that bear a vague resemblance to your sleeping bag, but it’s a highly functional layer that so far has kept testers warm without overheating them, even when they were running and cycling.
Look for Polartec Alpha in clothing from 66º North, Eddie Bauer, Eider, Mammut, Marmot, Montane, Mountain Equipment, Rab, Ternua, Terry Bicycle, The North Face, Trangoworld, Vaude, and Westcomb in fall 2013.
Rab’s Strata Hoodie, pictured above, has a stretchy Pertex Microlight 20D outer shell with comfort stretch, 80 grams of Polartec Alpha, and body-mapped woven nylon and poly-mesh inner layer. The hood fits over or under a helmet, and the chest pocket doubles as an integrated stuff sack. Available September 2013, 15oz (men’s L), $225; us.rab.uk.com.