As anyone who has ever shopped for outerwear knows, there are tons of waterproof, breathable options: GORE-TEX, eVent, H2No, Hyvent, Precip, Gelanots, c-change…the list goes on. So just what are we looking for here?
Waterproof breathable fabrics come in a few main derivatives: ePTFE based laminates, PU laminates, and polyester coatings. For our purposes, we’re going to split the technologies into three main categories: (1) GORE-TEX, (2) eVent and (3) the rest (PU laminates) as these technologies dominate the ski/snowboard outerwear industry. We’ve been pretty thorough with GORE-TEX, and for good reason, since it forms the basis for the majority of modern waterproof breathable (WP/BR) technologies. But let’s get to eVent and PU laminates.
eVent (pictured above in image #3) uses an ePTFE membrane just like GORE-TEX. eVent differs in the way it addresses the original GORE-TEX fouling issue. Instead of adding a whole new PU layer on the underside of the ePTFE, eVent uses an oleophobic coating over the ePTFE to keep contaminants away from the membrane. The chemistry is quite complex and out of the scope of this article (the application involves supercritical fluids, a very interesting branch of chemistry. Google it.) For now, we can think of this coating as slathering some paint on a strainer; the holes of the strainer are all still there, but the original material is now covered by this new coating. In the case of eVent, this prevents the membrane from becoming contaminated. Nice.
So it seems as if eVent has sidestepped the major breathability bottleneck of GORE-TEX, with fundamentally better technology, right? Well, in short, the answer is Yes, with a big BUT….We’ll talk about that later in the “Performance Ratings Debunked” section.
The third common waterproof/breathable technology is the PU coating. The same coating that GORE-TEX uses to protect their ePTFE can be used on its own to achieve very satisfactory results. The laminate ends up being significantly thicker than the layer GORE-TEX uses. However, it does not require diffusion across the ePTFE membrane as an added step in the water vapor transmission process. Most proprietary membranes like Patagonia’s H2No, and The North Face’s Hyvent, are derivatives of PU membranes. This technology is easy to manufacture, quite durable, and produces good results—a perfect recipe for product viability. Chances are good that if you have a piece of outerwear touted as waterproof/breathable, you have a PU laminate or coating in your garment.
DWR, Where the magic happens
So you just bought a jacket that claims 20K waterproofing, and you’re stoked. You take it out on the hill, and at the end of the day, the jacket is heavy with water. Your brand new jacket has “soaked through.” Furious, you call the shop you bought it from and tell them what BS the product claims are and that this jacket isn’t waterproof at all.
But let’s look at what is actually happening.
We know that this jacket is probably a PU garment, which means it has a nylon face fabric bonded to the PU layer. We also know the actual waterproof and breathability characteristics come from the laminate and that the nylon face fabric is there for durability and support only.
The “20K” advertised by the manufacturer only references the performance characteristics of the laminate and has nothing to do with the nylon face fabric. The amount of water that the nylon face will repel has absolutely nothing to do with the performance of the laminate. So what actually happened to your new jacket?
The jacket you bought came equipped with a poor quality water resistant coating (WR), which allowed moisture to saturate the nylon outer fabric. Your jacket (in all likelihood) never actually leaked, and maintained its advertised “20K” waterproof rating, even though it was completely soaked.
The WR serves multiple purposes: it keeps your jacket from feeling damp, it maintains the breathability of the garment (a soaked through jacket has nearly no breathability), and it keeps your jacket considerably cleaner from water-based dirt and grime. A good WR is absolutely essential for a high performance jacket.
Today, manufacturers use what is known as a durable water repellent coating (DWR). This means that the coating won’t wear away as easily as a standard WR. Generally, a DWR will retain 80% of its “new” condition performance after 20 washes.
In short, the waterproof rating and the DWR have absolutely no relation to each other! Even so, people tend to confuse waterproofing performance with DWR performance. To the average (and even above average) consumer, the waterproofness of a material is judged by the DWR, not the laminate. It doesn’t matter how good the laminate is, if the DWR on the fabric is poor, you will not be happy with the performance of your garment.
Along with understanding the differences between laminates and DWRs, it is important to note that a jacket is only breathable as long as its DWR is working effectively. A soaked through textile has little to no breathability.
Companies like GORE-TEX and eVent use a proprietary DWR coating and spend millions of dollars in research to perfect this part of the product. In many ways, it is the most important piece of a waterproof breathable textile, and can make or break a piece of outerwear.
The bad news, however, is that it is almost impossible to know what you’re getting when you buy a product, because there is no standard for measuring the performance of the DWR.