What is Polartec Alpha insulation?

Have you ever strode into a river in winter, stood fully immersed for 15 minutes, dragged yourself out, then just kept walking until dry again? We haven’t either, but that was one of the tests used to prove the insulating properties of Polartec Alpha insulation.

polartec alpha cycling jacket

Polartec Alpha was developed for the US military’s exacting requirements and that, along with lab tests and cold weather combat training in Kodiak, Alaska, was one of the US Army’s tests when it was looking for new cold weather clothing for its special operations forces in 2012.

But Polartec Alpha is also commercially available and used in a wide range of products for outdoor activities in extreme environments. We use it in our Feel the Benefits insulated gilet and Test Your Mettle insulated jacket, both available for men and women. It has some unique properties that make it especially useful for outdoor sports that mix vigorous, heat generating activity with less active periods. 

That usage pattern makes it a really good insulation layer for cycling in cooler conditions, where you don’t want to overheat on climbs but need to stay warm on descents too. It’s got great eco credentials as well, as it’s available made from 100 per cent recycled materials.

polartec alpha insulation diagram

What makes Polartec Alpha such an effective insulator for active sports?

Polartec Alpha is made of lightweight lofted PET strands which are bonded to an open mesh supporting layer. The fleecy plastic traps warm air, providing the insulation, while the mesh keeps the insulation in place.

If you’ve ever tried to sleep in a damp down sleeping bag you’ll know that down tends to clump together when it’s wet. Most synthetic insulation can migrate around and clump too. Clumping means that you’re left with cold spots so it’s usual for insulated pieces to be constructed with sewn baffles that help hold everything in place, but this too leads to cold spots at the seams.

That’s not a problem with Polartec Alpha; the mesh core means that the insulation stays in place without baffles and won’t clump, so you don’t get cold spots. Not having baffles also means that there's no barrier to heat dispersing more widely through the insulation when you're exercising.

One of the military’s needs was a fabric that would keep special forces soldiers warm at rest in the cold, but wouldn’t cause them to overheat once they started to move again. With body armour and packs worn over their insulation, they couldn’t easily stop and strip off a layer.

polartec alpha heat diagram

So Polartec Alpha is designed with a very open structure to its insulation and the mesh layer. That means that once you start to move, there’s enough airflow to keep you from overheating but the colder air flowing in from the outside is dispersed and slowed down, so you don’t get cold. At the same time, there’s enough airflow to remove humid air and body heat, helping to stop you from getting sweaty. 

The insulating strands are hydrophobic too, which means that Polartec Alpha doesn’t wet out, which is why soldiers can climb out of rivers and wait to dry out. It also means that the material stays light and doesn’t get damp from sweat.

All of that’s ideal for insulated cycling clothing; there’s uniform coverage for warmth, plenty of airflow while riding and no tendency to get clammy if you’re out in damp conditions or working hard to crest a climb.

cycling with polartec alpha insulated jackets

The open structure means that Polartec Alpha is lightweight for the warmth it provides - always a hot button for cyclists. It’s also compressible, so it’s easy to pack when you’re not using your Polartec Alpha piece and its linked structure means that it’s very durable and so won’t lose its insulation properties over time.

Environmental credentials

Polartec offers Alpha fabrics made from either 100 percent recycled PET or with a minimum of 50 percent recycled PET. That’s the plastic that drinks bottles are made from and Polartec says that it’s recycled 1.7 billion PET bottles into its range of performance fabrics since it started producing its first fabrics from recycled yarns.

Polartec says that it also repurposes 95 percent of its remnants from making its fabrics into other, lower value, products like flooring, mats and insulation. It’s bluesign and Oeko-Tex certified.

That’s a perfect fit with our philosophy here at Pearson, where we always aim to use the most environment friendly materials and products we can find, while still producing high performing cycling products like our winter gilets and jackets.


Shop Polartec Alpha items in our new Autumn Collection

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