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.