New PolarTec AirCore

A bit more in their press release:

https://www.textileworld.com/textile-world/nonwovens-technical-textiles/2025/09/polartec-aircore-harnesses-the-power-of-air-to-defy-performance-limits/

With an industry-leading Moisture Vapor Transmission Rate (MVTR) of over 25,000 g/m²/24 hours* and air permeability ranging from 0.4 to 1 CFM**, Polartec AirCore provides unmatched performance during high-intensity activities while repelling water from the outside***. Furthermore, the lightweight material and superior stretch enables unrestricted movement, making Polartec AirCore an ideal choice for outdoor enthusiasts, explorers, and anyone on the move.

…

* MVTR measured according to JIS L1099, B1.

** Air permeability (CFM) measured according to ASTM D737 at 125Pa.

*** Water Repellent – Minimum 4 spray rating as is, per  GB/T 4745-2012 (ISO 4920-2012, MOD).

Note they are saying “water repellant” not water proof.

Does sound interesting.

Blurring the line between wind shells and rain shells could mean getting away with just one of them, more often.

“Stretchy and silent” has me hoping some hunting gear makers will jump onto this as well.

This sounds like a continuation of the PowerShell line.

The MVTR rating is mediocre, comparable to a poor non-porous urethane membrane.

The level of water resistance is not well defined.  The highest score on the spray test is 5. This got a four. The test consists of loading a quarter liter of water into a funnel.  The water sprays onto the fabric from a height of six inches.  After the fabric is removed from the test apparatus, it is turned upside down and tapped to remove loose drops and then photographed.  This got a four.  Here are the ratings:

0 — Complete wetting of the entire face of the specimen; 1 — Complete wetting of the entire specimen face beyond the spray points; 2 — Partial wetting of the specimen face beyond the spray points; 3 — Wetting of specimen face at spray points; 4 — Slight random sticking or wetting of the specimen face; 5 — No sticking or wetting of the specimen face.

This test does not simulate the forces of even a light rain and does not provide much confidence in the water repellency of the fabric.

I contend (as has Patagonia), that an air permeability rating of 5 or less means that the fabric is essentially impermeable.  It will provide no practical ventilation to the wearer. So, Polartec’s claimed air permeability of less than 1 CFM/Ft2 means you should not expect any ventilation from this fabric, even in a strong wind.

If I can ever obtain a garment, I am happy to test it, but this just sounds like a windshirt with poor breathability and water resistance.

I am entirely OK with WPBs that are not 100% waterproof. I prefer them for light weather, as long as they are more breathable (Ex: older AscentShell, EE Visp). Polartec may have started it with NeoShell, and many have followed. They just didn’t TELL US what they were doing, which led to a lot of customer confusion and frustration.

It is refreshing that they are telling more of the story this time.