This site has limited support for your browser. We recommend switching to Edge, Chrome, Safari, or Firefox.


Waterproof Breathable Fabric Development

By Chris Pew on

Every season we re-evaluate the performance and function of our garments. We are all backcountry skiers and snowboarders; testing gear and improving the function is what we’re passionate about. This season - Fall/Winter 2019 - we are unveiling a new 3-layer fabric that is the result of 10 years of creating and testing garments for backcountry skiing and snowboarding. 

We’re naming this technology the PNW 3L because it Performs in Nasty Weather.   

What’s in PNW 3L? The Details.

The performance gains we were trying to achieve in our new fabrics is an increase in the durability of the waterproofing of the fabric; particularly, the longevity of the waterproofing after prolonged use and abuse. We focused on updating the face fabric to provide the most important layer of protection, and then we updated feel and chemistry of the fabric slightly. Overall, we achieved a much more dependable and durable laminated fabric. 

Increased Protection

The crux of this innovation is a tightly woven nylon face fabric. The fabric is 100% nylon, oxford weave, that is especially densely woven; leaving little space for water droplets to penetrate. The weave itself is so durable and water-resistant that it stands up well to repeated use, even after the DWR coating has worn off. This was a key improvement for us and will add a lot of value to the lifetime of the garment.

Dependable Chemistry

The membrane of the PNW is a similar composition to our Dermizax membrane from last season, our tried and true nonporous, hydrophilic polyurethane chemistry. The benefit of this chemistry is that it still performs when its stretched, stressed, and dirty, all the things that we know will happen to our gear. 

The final package is rated at 20k waterproof / 20k breathable (MVTR). The densely woven face fabric has slightly decreased the breathability results from lab tests, but we’ve been very pleased with breathability in the field. The fabric is a little lighter and denser, which gives it a feeling of less insulation while you’re touring. Most importantly, the durable face fabric will protect the membrane against being compromised by dirt and oils, protecting the lamination and improving the lifespan of the garment. 

Tried and TREW

We’re less interested in how many grams of vapor can escape a square meter of fabric in a lab setting in a 24 hour period (gr/m2/24hr), than we are invested in finding the best solution to keeping backcountry skiers and snowboarders dry and comfortable during long days touring, climbing, and shredding. Ultimately, we’re measuring the success of a fabric or product in the tangible comfort that ourselves, our athlete testers and our customers can report.

How fabrics are actually measured

The two key tests that provide metrics for most outdoor fabrics are the hydrostatic head (waterproof) and the moisture-vapor-transmission-rate (breathable) tests. In each case, the test is done in a lab setting, and they evaluate a very specific characteristic of the fabric. We believe that these tests do provide an accurate assessment of the overall quality of the fabric, and therefore they are helpful in both our evaluation of the fabric and the buyer’s journey. However, because these tests are performed in a lab setting, and for reasons expanded on below, they aren’t always the best indicator of real performance in the field. There is NO SUBSTITUTE to wear-testing. And in some cases, merely picking the fabrics that have the best results to lab tests, won’t deliver the best performance for the wearer. 

Why lab tests aren’t perfect: Waterproof Test

The hydrostatic head test measures a fabric’s resistance to water penetration under a certain amount of water pressure. The fabric swells under the water pressure; when droplets are able to push through the fabric, the pressure is noted and the test is repeated three times. This is an accurate measure for the membrane quality, lamination consistency, and ability for the woven face fabric to resist water, but applying these results to end-user is tricky at best. Unless you find yourself using a swatch of your jacket fabric to clamp the end of a high-powered hose, it is hard to imagine a real-life scenario in which your fabric will be tested in such a way. The difference between a fabric with 10k and 20k waterproofing is tangible, the tests can help get you that far, but in the 20k waterproof category, there is a huge variance of real-life performance. Thus the importance of rigorous wear-testing and evaluation. 

Why lab tests aren’t perfect: Breathable Test

The MVTR (moisture-vapor-transmission-rate) testing measures the amount of vapor that can pass through a square meter of fabric in a 24 hr period. MVTR is more of a category of testing, within which there are a few variations of procedures: the Upright Cup (A1), Inverted Cup (B1 or B2), and Sweating Hot Plate or RET test. Most consumers are familiar with the metrics behind the A1 and B1/B2 tests, being measured in gr/sqm/24hrs, and thus this has become the standard. At TREW, we have come to trust the performance of non-porous hydrophilic membranes manufactured by Japanese textile mills. These mills will commonly focus on the B1 version of the MVTR test because the membrane will actually come into contact with the water during the test. This favors the “water-loving” characteristics of hydrophilic membranes, and to be fair, is a valid test for the comfort of the wearer, measuring the ability to push actual sweat through the fabric as opposed to just vapor. In our opinion, therein lies the flaw of the B1 tests, it doesn’t measure the perceived ability for a fabric to regulate comfort before vapor turns to condensation.  

The TREW Wear Tests 

The important considerations for wear-testing garments is to simulate, as best we can, the environment that our customers are likely to encounter. Fortunately for us, this means getting up on the hill as much as possible, a healthy mix of spinning laps at the resort and backcountry skiing and snowboarding. The best environment to test garments for us is a backcountry hut trip; we’re able to get a higher concentration of skinning and climbing in a 3-5 day period, allowing us to focus on the relative performance of comfort of different garments and fabrics. 

The other key process to wear-testing is putting the garments through at least 10 washes in a home machine with detergent. This simulates years of use and allows us to see how the fabric will perform after several seasons. 

Head-to-head tests

After picking our favorite fabrics from the first round of wash and wear tests, this past season we created half-and-half garments to test our favorite fabrics head-to-head. With these garments, we get to compare the relative comfort, ease-of-movement, and, most importantly, the durability of each garment. Nothing can compare the relative wear of two fabrics better than a single garment made with two fabrics. 

What we noticed during our trials is that the new PNW fabric sheds snow and moisture quicker than our old fabric. We also liked how “light” the PNW fabric felt to the wearer, even though the actual finished lamination was a similar weight. I think the fabric being much denser and less lofty contributes to it feeling lighter and less insulating. Again, this is an observation you can only make after wearing the fabric. 

We're pumped to bring this new fabric to our best-selling outerwear products. We think it solves some key pain points that we've been hearing from customers and will generally improve the longevity and lifetime of the garment. It's one of the most dependable and durable waterproof/breathable fabrics we've used.

These are all of the products available with PNW 3L:

← Older Post Newer Post →


  • Bibi on

    where can i source this type of material

  • Bjorn on

    Fantastic info- thank you!

  • Chris | TREW on

    Thomas, thanks for the comment! “Better” is relative, depending on the intended use of the products. We kept the Dermizax for the Capow line because we do trust the performance and it has a nice stretch for uphill mobility. However, we believed the face-fabrics of the available Dermizax laminations sacrificed protection from the elements and durability. This motivated us to develop and test new fabrics that would provide better waterproofing longevity. Thus was the PNW fabric born!

    We believe the PNW fabric is “better” for our average customer, spending more days in the resort than in the backcountry. It’s going to be more durable and shed moisture from the types of storms you would hope not to encounter in the backcountry but might endure in the resort. I hope that helps! -Chris


    If the new PNW fabric is better than last year then why doesn’t the Capow use it? Or are all the new coats and pants using it?

Leave a comment

Please note, comments must be approved before they are published
Back to The Journal