Everything You Need to Know About Waterproof Fabrics
Waterproof fabric technology has come a long way since its
humble complicated chemical beginnings in Bob Gore’s laboratory. I’ll spare you the details of how intermolecular forces prevent water molecules from penetrating a porous membrane, or how polyurethane can be considered breathable due to solid-state diffusion (however if you’re like me and really want to know about this stuff, click here). What I will give you is a practical and detailed outdoor adventurer’s guide to understanding technical waterproof fabrics.
Before we get started…
There are some important terms that you need to be familiar with before diving into a discussion about waterproof fabrics. Come back here for reference if you encounter a term you’re unfamiliar with.
Face Fabric: Generally a nylon/blended fabric on the outside of the garment. The face fabric protects the waterproof membrane and provides a surface on which to apply a DWR. It can also be engineered to be visually appealing. It IS NOT a waterproof layer.
DWR (durable water repellent): This substance is applied to the exterior of the face fabric. It causes water to bead up and fall off rather than absorb. A high-quality DWR keeps the face fabric from wetting out and maintains breathability. Worn-out or low-quality DWR coatings are the primary reason that waterproof garments fail. A “wetted out” waterproof garment cannot breathe.
Membrane: A layer of waterproof material. Membranes are usually made of ePTFE or polyurethane. It is either bonded to the outer layer of the jacket or suspended between two fabric layers.
Laminate: A membrane bonded to a face fabric.
Fouling: Describes what happens when the pores of a waterproof membrane become clogged with foreign particles, like salt from users’ sweat or oils from their skin. Fouling can greatly affect both the membrane’s ability to breath and its level of waterproofness.
Tricot: A hydrophilic (water loving) layer that actively pulls moisture away from your skin. Tricots are generally the third layer of 3L fabrics.
Also, you should know the difference between
Water-Resistant: These fabrics are tightly woven or manufactured in such a way as to resist penetration by moisture. This won’t keep you dry in much more than a snow flurry or misty morning fog. These fabrics offer the least amount of protection against moisture. However, if you add a DWR finish, the fabric can become…
Water-Repellent: This means that water can’t easily penetrate the fabric. In terms of fabric, water repellency is generally accomplished with some sort of coating or finish rather than being a component of the fabric itself. DWR is the most common method of adding water repellency. Which brings us to…
Waterproof: Under pressure, waterproof fabrics are impervious to water… to a certain degree. How much pressure a fabric can endure before water starts to leak through is used to “rate” how waterproof the fabric is. Waterproof fabrics rated at 10,000mm are waterproof to a pressure of about 14psi, for reference. In order to be considered waterproof, a fabric must also have sealed seams. Some companies use heat welding rather than stitching to create seams to maintain the fabric’s waterproofness. Others tape the stitched seams of their fabrics to create a waterproof seal. Quality of seam sealing and waterproofness of zippers and other enclosures will affect how waterproof the final garment will be.
Got it. Now what are waterproof fabrics made of?
There are two primary membrane materials that dominate the waterproof fabrics market. Virtually all major waterproof/breathable (WPB) fabrics are constructed with either an ePTFE membrane, a PU membrane, or a combination of the two.
Expanded polytetrafluoroethylene, or ePTFE, is a material that was developed by Bob Gore and used to create the first Gore-Tex fabrics in 1978. Bob Gore discovered that when PTFE is expanded (stretched), it creates a waterproof “web” with millions of microscopic pores. These pores are 20,000 times smaller than a water molecule, but 700 times larger than a molecule of water vapor. This means that liquid water cannot pass through the membrane, but gaseous water vapor can. ePTFE membranes tend to be more breathable than solid PU membranes, but are more prone to fouling.
Polyurethane, or PU, is monolithic. This means it has no holes or pores. However, it is also hydrophilic (water is attracted to its surface) which allows PU membranes to maintain breathability via a process known as molecular wicking. This process pulls moisture away from the skin and allows it to slowly pass through the entire membrane. Solid PU membranes tend to be less breathable than ePTFE membranes. Their breathability is dependent on external temperature and a high concentration gradient. Peak function occurs around freezing in dry environments. Basically, you’ll have to start sweating before water vapor is going to be able to pass to the outside of the fabric. It also means that a PU membrane isn’t going to function that well in really humid environments. However, some manufacturers are now developing air permeable membranes using porous PU laminates that drastically increase “breathability” over solid PU membranes.
But you can’t just wear these “membranes” on their own, can you?
Nope, you’re correct. Waterproof fabrics are generally manufactured in one of three standard constructions. Each construction involves different “layers” that contribute to either waterproofness, breathability, or protection.
- 2L fabrics consist of a face fabric bonded to a WPB membrane. This is backed by a lining (mesh or nylon) that helps minimize direct contact with skin and protects the laminate from fouling. 2L fabrics dominate the market due to ease of production.
- 3L fabrics consist of a face fabric, bonded to a WPB membrane. This is then bonded to an interior tricot layer that provides increased breathability over 2L fabrics. 3L fabrics are lighter weight than 2L fabrics due to not having a lining. They are also more durable due to the bonded tricot layer.
- 2.5L fabrics consist of a nylon face fabric, bonded to a WPB membrane. This is backed by printed lining on the skin side that helps protect the membrane. These are generally lighter weight than 3L fabrics but may be less comfortable to wear.
How do I know which type of fabric is best?
Dig deep enough when researching outerwear and you will come across ratings for waterproofness and breathability. There are different tests available, so it can be difficult to determine the quality of a product using these numbers. Nevertheless, here’s some information on the ratings.
Hydrostatic head is the most common method used for determining waterproof ratings. We will use hydrostatic head ratings to discuss waterproof fabrics in this article. You’ll find ratings that range from 5,000mm all the way up to 20,000mm+. The number of millimeters represents how much water pressure the fabric can withstand before it begins to leak. It is important to note that this number rates the waterproofness of the membrane. It does not take into account the face fabric or DWR.
Let’s also consider for a moment what this rating actually means. Many manufacturers (looking at you, Gore-Tex) market really high waterproof ratings: 20,000mm and beyond. However, waterproof fabrics with a rating of just 10,000mm are waterproof up to a pressure of 14psi. Taking into account heavy rain and high wind, it’s unlikely your rain shell is ever going to experience pressure upward of 2psi. You’re hiking in it, not swimming in it. Even the pressure of your pack straps or the force exerted on your pants when you slip and bust your butt is still unlikely to exceed 14psi.
Before you get hung up on a company touting the highest breathability ratings on the market, you should know that there is no industry standard for these ratings. Several tests exist that can yield vastly different results. Manufacturers tend to use whichever test shows their fabric in the most favorable light. Can you really blame them? The point here being: take these ratings with a grain of salt. The two most common tests are:
The moisture vapor transmission rate (MVTR) measures how much water vapor can pass through a fabric in a 24-hour time period. This number is generally expressed in grams/meter/24hours. The higher the number, the more breathable the fabric is supposed to be.
Resistance to evaporative heat transfer (RET) is another number that is used by some companies to measure a fabric’s breathability. In this case, a lower number translates to higher breathability.
What all this means
You want an outerwear garment with the highest level of waterproofness and breathability that you can find and afford. However, these numbers are not the end of your research. Many factors can affect a fabric’s ability to keep you dry. A fabric with a high waterproof rating (20k+) is going to be useless if the DWR is low quality or worn off. A fabric with a high MVRT isn’t going to breath well if the membrane is saturated with oils from your skin. Neither excellent waterproofing nor high breathability ratings are going to keep you dry if it’s hot, humid, and raining because the moisture differential required for vapor diffusion across the membrane isn’t going to be there.
What types of waterproof fabrics are out there?
In the late 1960s Bob Gore was one of the pioneers of the waterproof/breathable (WPB) fabric industry with his discovery of the stretchy properties of PTFE. Fast forward to present day and there are now several companies that are dedicated to manufacturing high-quality technical WPB fabrics for outdoor adventure clothing, though Gore-Tex remains the most well-known and successful brand in the industry. As new technologies emerge, both new and existing companies continue to invest millions of dollars into research and development to stay on the cutting edge. Here, I’ll discuss the differences between these companies to give you an idea of what each of them is offering.
Gore-Tex is arguably the most popular and most well-known company producing waterproof fabrics. At this point, Gore-Tex is basically a household name. Gore-Tex fabrics utilize an ePTFE membrane with an extremely thin polyurethane coating to create a WPB fabric. These fabrics are available in standard 2L and 3L constructions, along with a Gore-Tex specific “z-lining” construction. Paired with one of Gore-Tex’s patented backing options, these constructions offer options for pursuits ranging from day hiking to ski mountaineering.
Gore-Tex stands out in the waterproof fabrics market due to its unique construction and its industry-leading Guaranteed to Keep You Dry Promise. This guarantee ensures the consumer that any Gore-Tex product purchased will keep you dry for the useful lifetime of the product. Basically, it’s a guarantee on waterproofness. GoreTex partners with multiple high-end outdoor apparel brands including The North Face, Arc’Teryx, Marmot, and Patagonia.
Owned and produced by General Electic, eVent fabric technology brings something entirely different to the table. Unlike Gore-Tex, eVent does not incorporate a hydrophilic PU coating into its waterproof membrane. Instead, eVent protects the ePTFE membrane with an oleophobic (oil resistant) coating. This is the basis of their patented Direct Venting technology, which reportedly begins breathing immediately rather than having to wait for a moisture gradient to be reached. This direct venting “dry system” is the feature that sets eVent apart from other major technical fabric brands.
eVent has created WPB fabrics that range from 10,000-30,000mm waterproof ratings and from 10,000-30,000g/m^2/24hrs breathability ratings. eVent boasts three distinct waterproof fabrics: the DVexpedition, DValpine, and DVstorm. Each of these is designed with a specific use in mind, ranging from high-altitude expeditions to trail running. Several top brands are utilizing eVent’s fabrics, including Rab, REI, Eddie Bauer, Sea to Summit, Granite Gear, and many others.
Changing things up once again, we move to Pertex, which forgoes the ePTFE membrane and instead uses a PU laminate to create its waterproof fabrics. Pertex’s fabrics are available in 2L, 2.5L, and 3L constructions. These fabrics are marketed as waterproof, windproof, breathable, and packable. Several name brand clothing manufacturers such as Rab, The North Face, Outdoor Research, Montane, and Patagonia partner with Pertex. Fabrics developed by Pertex come with waterproof ratings from 10,000-20,000mm and range from 6000-20,000g/m^/24hrs breathability ratings. Shield, Shield +, and Shield Pro are the three distinctive fabric options produced by Pertex. They provide suitable fabrics for a variety of conditions, with options for intense mountain sports, fast-paced activities, and long-term pursuits such as backpacking.
Polartec’s Neoshell membrane entered the market as a WPB option for “adventurers who move and sweat, a lot.” The Neoshell membrane is made up of a porous polyurethane. In addition to allowing water vapor to pass through, Neoshell also moves air through the membrane via convection. This makes Neoshell an air permeable membrane, and it was the first company to market itself as such – though eVent is also considered air permeable and has been on the market longer than Neoshell.
In addition to its WPB attributes, the Neoshell membrane also boasts a four-way stretch feature that is purported to be more comfortable to wear than other comparable hard-shell garments. Polartec Neoshell partners with well-known brands such as Altra, Marmot, Eddie Bauer and is continuing to branch out into the WPB marketplace.
While many clothing manufacturers stick to using fabrics designed by companies like Gore-Tex or eVent to create their products, several bigger-name clothing manufactures are creating their own proprietary fabrics.
Marmot has several proprietary fabrics utilizing a variety of technologies at many different price points.
Marmot’s PreCip fabric leads the market in budget-friendly WPB technology. This is a 2.5-layer construction that incorporates a protein coating on the interior of the fabric to increase comfort and dryness.
Marmot’s MemBrain laminate utilizes a 2L PU membrane and markets a breathable, durable waterproof fabric that won’t break the bank. In addition, the Membrain Strata offers a 2.5-layer construction that Marmot advertises to be “100% more breathable than comparable 2.5 layer fabrics” – though I’d take that with a grain of salt.
With its Nano Pro and Nano Pro Membrane technology, Marmot is branching out into the arena of air permeable WPB fabrics and competing with manufacturers such as Polartec and eVent. Like Polartec Neoshell, Marmot utilizes a porous PU material to make this line of fabrics both waterproof and breathable. The less expensive option is the Nano Pro, which is a 2.5-layer construction in which the PU is applied directly to the face fabric. The Nano Pro Membrane is a 2.5-layer construction that utilizes a PU laminate bonded to the face fabric. The Nano Pro Membrane is purported to be significantly more breathable, and both options are durable and protected from fouling due to the oleophobic properties of polyurethane.
Dry.Q is Mountain Hardwear’s response to the WPB industry and is utilized in several of its outerwear garments. This fabric comes in three configurations:
Dry.Q Elite is extremely similar to eVent in both functionality and performance. This is due to the fact that MH partnered with GE to manufacture this specific fabric. Like eVent, it boasts high breathability due to the elimination of the PU coating found in most ePTFE fabrics.
Dry.Q Active and Dry.Q Core do not utilize the GE air permeable membrane. Instead, they are manufactured to industry standards for WPB garments. The Active is designed specifically for aerobic backcountry activities while the Core is suitable for a variety of uses
DryVent is a proprietary fabric manufactured by The North Face. Available in 2L, 2.5L, and 3L constructions, DryVent garments are marketed for a variety of uses.
Patagonia’s proprietary WPB fabric is found in many of Patagonia’s outerwear garments. Patagonia puts H2No fabrics to the test in their “Killer Wash.” This series of laboratory tests is designed to simulate years of use in harsh conditions. Garments manufactured with H2No technology are available in 2L, 2.5L, and 3L construction and are suitable for a wide range of pursuits.
AscentShell is a proprietary fabric manufactured by Outdoor Research. OR describes an “electrospun membrane” to be what makes this fabric stand out from the WPB pack. In simple terms, an electrical charge is applied to a standard PU membrane, causing billions of microfibers to develop. These microfibers of PU are used to create a WPB membrane that is also air permeable.
Outdry Extreme fabrics are Columbia’s technologically advanced response to the WPB fabric industry. Pretty much unlike anything else on the market, this may be one of the more revolutionary fabrics produced to date. Originally released in 2016, the Outdry Extreme fabric eliminated the face fabric/DWR combo and moved the membrane to the outside of the fabric (gasp!). What this accomplishes is the elimination of the need for DWR, which is prone to wear off with extended use. Outdry Extreme fabrics use a proprietary polyurethane-based membrane that has been strengthened to withstand exposure to the elements. A wicking fabric is heat-bonded to the inside to keep you from feeling clammy.
The waterproof fabrics market has long been dominated by the WPB giant Gore-Tex. However, as good as Gore products are, there is still a lot of room for improvement in this industry. New technologies such as eVent, Neoshell, and Columbia’s OutDry extreme are pushing the boundaries of what can be done to maintain waterproofness and improve breathability and air permeability. The ultimate goal of all of these companies is to keep you dry – protecting you from both external moisture and internal water vapor.
How do you know which fabric is right for you? Choose outerwear made with fabric that has a waterproof rating of at least 10,000mm, boasts high breathability, feels good on you, and is marketed and designed for the backcountry adventure that you are seeking. Online gear reviews are a good place to start, since nothing speaks to performance like real-world experience. Now, take your newfound knowledge of waterproof fabrics out there, find yourself a shell, and get on with your adventures!
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