One of the more interesting new fabric technologies out there is Polartec Alpha - a sort of alternative to puffy-type synthetic insulation that's designed to be breathable enough for active use in cold conditions - and Swiss brand Mammut has two new jackets using it due out this autumn, 2013.

The  new Biwak Light (ladies) and Eigerjoch Light (mens) jackets have already landed one of Polartec's internal Apex Awards for the best use if its own fabrics. Alpha is different from conventional synthetic insulation in that it's a sort of stable sandwich of insulation rather than bats of fluffy stuff and that means it's possible to use more breathable fabrics around it, hence the improved breathability properties.

We've been using a couple of prototypes over the past six months or so and it works very well, though it's not as outright warm as more conventional synthetics it's definitely far more breathable and it dries fast too.

Windproof Outer Fabric

The Eigerjoch Light - not to be confused with the full-weight down-filled Eigerjoch, which would of course be easier if it had a different name - and its more feminine cousin is designed for stop-go stuff where you need a combination of breathability and insulation. 

Unlike some Alpha garments, the outer layer is completely windproof Pertex Quantum for a bit more weather protection so it can be worn either as a mid layer or an outer, but it has Polartec PowerStretch inserts at the side and back for good breathability and easy movement.

There are hand-warmer pockets and a single chest pocket, no hood, but high reach sleeves and thumb-loops should do the business in climbing situations. Weight for the men's version is a claimed 410g.

The women's Biwak Light is about 50 grammes lighter, but shares the men's jacket's athletic fit and featurs but with a women's-specifit cut.


Don't confuse either with their non 'light' cousins which are full-on down and fiberfill jackets - they have more differences than similarities as far as we can see. 

Prices are slightly terrifying at £220 for either option. More information at