Construction 101: 2, 2.5, and 3-layer Fabrics
Nearly every manufacturer boasts about how many layers their jacket features, but what does that even mean and how should this affect what products you consider?
Most rain shell fabrics use a 2, 2.5, and 3-layer designs, even if they might only look like a single layer when you hold them at the store; that's because these layers are tightly-sandwiched. Whether 2, 2.5, or 3-layer fabrics, these designs share most of their construction qualities; there is only a small difference on the inside-facing side of the garment. All three styles feature an outer shell fabric, commonly referred to as a face fabric which is coated with a chemical Durable Water Repellent (AKA: DWR, more on this below) finish to help keep the outer layer from absorbing water. The second, or middle layer is the actual waterproof layer, whether that be eVent, Gore-Tex, another membrane, or coated fabric. Universally, these nearly get placed beneath the outermost face fabric layer; so yes, you can't see the waterproof layer from the outside. The third and innermost layer is where all of the differences lie.
As we mentioned above, 3-layer fabrics feature an external DWR treated face-fabric - a waterproof breathable membrane in the middle and a polyurethane (PU) film or other similar backing. This third layer's goal is to keep sweat and oils from clogging the microscopic holes in waterproof-breathable layer, reduces breathability and make the user feel wet from sweat that they might think is coming from the outside.
The advantage of three layer fabrics is they are typically more durable overall because of the innermost layer, which protects the pores in the waterproof membrane from clogging (longer), thus maintaining better breathability between washings. That said, 3 layer pieces are not always as breathable and are often heavier than many of their 2.5 layer counterparts.
2.5 Layer Fabrics
Outer garments that feature a 2.5 layer construction look similar to those that feature a 3 layer design (with the exception that they may feel slightly lighter and more subtle). Jackets that feature a 2.5 layer construction have the same outermost layer that has been treated with DWR, protecting the waterproof layer. Then, an exceptionally thin polyurethane laminate or other coating is placed on the inside to help protect this layer from sweat, grime, or other oils that could clog the pores. This layer is often "painted on", which is why it's considered a half layer, even if it covers all of the inside surface area.
Jackets that feature a 2.5 layer construction offer similar breathability to 3-layer jackets, though they sometimes feel marginally clammier. Why? Because the innermost layer doesn't do quite as good of a job at "absorbing" and transferring sweat that has been created by the wearer. 2.5 layer jackets are typically slightly lighter and more subtle, but often not quite as durable (and must be cleaned more frequently to maintain breathability).
2 Layer Fabrics
These fabrics have the same DWR face fabric bonded to a waterproof-breathable layer with a loose liner hanging on the inside that is typically mesh; this works to help protect the membrane or coated material. These jackets are less expensive and more moderately priced. They breathe well, but are heavier, bulkier, and not ideal for active outdoor users.
Gore-Tex is the oldest and most widely know waterproof-breathable fabric and has basically become the Kleenex of the waterproof-breathable fabrics world. On a very basic level, Gore-Tex is a polytetrafluoroethylene (or ePTFE for short) membrane stretched out to an extremely specific dimension. Water vapor can escape, but liquid water cannot enter, due to both the sizes of the pores (which are 20,000 smaller than a water droplet), as well as the material's extremely low surface tension, which cannot absorb liquid water without tremendous pressure.
Polytetrafluoroethylene is also slightly better know by the DuPoint brand name Teflon. W.L. Gore is always trying to improve the product; in order to do so, the company has strict rules and restrictions for companies that want to use their product; in doing so, they keep up their reputation of "Guaranteed to Keep you Dry".
eVent is very similar in design to to Gore-Tex and is also an ePTFE based material. It was originally designed for industrial air filters by a company owned by General Electric before discovering it would make an fantastic waterproof breathable textile. Similar to Gore-Tex, eVent uses an external face fabric with a very similar polytetrafluoroethylene membrane. Where the big difference is in the inner-most layer: instead of using a solid material like Gore-tex (which uses a hydrophobic polyurethane (PU) film on the inside), eVent uses a secret propitiatory coating that protects the individual fibers without clogging the pores. The result is a more breathable ePTFE than Gore-tex, yet a product that needs to be washed more frequently in order to maintain better breathability.
Polyurethane or PU Films
New PU fabrics are quickly catching up to ePTFE membrane fabrics like Gore-Tex and eVent. The PU laminate acts as the waterproof layer and is very similar to the one laminated to the inside of a Gore-Tex jacket. If the PU layer is waterproof, why bother to add the ePTFE layer, you might ask? It's because when laminated to a ePTFE layer, it can be exceptionally thin; without it, it must be thicker in order to achieve the desired properties.
Three of the biggest advantages to garments featuring a fabric that relies on PU for its waterproofing is that they tend to be lighter, have the potential to be more breathable, and can be constructed with more stretchiness. Jackets and other outerwear featuring Gore-tex or eVent is much harder to do, and even the stretchiest ePTFE fabric is nowhere near as stretchy as a PU based one.
Coated fabrics are often used on price-pointed models and are nearly always less breathable and potentially less long-lasting than the above materials. It's worth repeating that the coated waterproof and breathable fabric still gets sandwiched inside the the jacket and can be made using a 2, 2.5, and 3 layer construction. Like PU coated fabrics, it can be made with stretchy textiles, allowing garments to have more range of motion.
Durable Water Repellent (DWR)
Durable Water Repellent (DWR) refers exclusively to the chemical treatment that has been applied to the exterior fabric (not the membrane or coated waterproof fabric) and its performance in resisting or beading up water. The goal of DWR is to help keep the external face fabric from becoming saturated, affecting breathability and giving the user a sensation of dampness. All waterproof fabrics feature a DWR as well as most water resistant textiles which can be found featured on insulated and softshell pieces. Most companies use fluorocarbons or fluoropolymer chemicals that are applied; they subsequently bond to the outside of the exterior fabric.
What is Waterpoof?
An easy answer would be "it can't let any water through"; however, the problem is water can have a variable amount of force. For example, even concrete can be cut by highly pressurized water, but we still consider concrete a waterproof material. Most rain generates around 2-3 PSI (PSI = pounds per square inch) of force. Rain in a severe storm (with 80+ mph winds found in a hurricane) can produce up to 10 PSI.
A manufacturer calculated that a 180-pound person creates around 8 psi sitting on the wet ground and 16 psi while kneeling. While in the outdoor recreation industry there is no official standard, the US Military requires that a fabric must be able to resist 25 PSI (or 16,700mm) to be considered waterproof; most manufacturers have used just that. What do those numbers look like? Even to simply generate 3 PSI? Imagine that a one-inch by one-inch box would have to be over seven feet high and filled with water while placed on a give fabric; this would generate 3 PSI.
Types of Waterproof Jackets
Here at OutdoorGearLab, we divide waterproof/breathable shell jackets into two categories: Rain Jackets and Hardshells. At the most basic level, price and fabric construction quality distinguish these categories from one another. Jackets generally cost about $90-$300 and typically feature 2-2.5 layer construction, while hardshells will set you back $350-$800 and typically feature 3 layers. Rain jackets are the affordable or lighter weight option for general use or applications where weight is more important, but the advanced hardshell fabrics are usually more durable and their features are more technically focused for alpine climbing and skiing.
Only two of the products we tested in this review uses a Gore-Tex fabric. The Outdoor Research Foray and Marmot Minimalist, which we rated the most durable products in the review, use Gore-Tex Paclite, an advanced 2.5-layer laminate. Three other jackets tested utilize a laminated fabric: the Patagonia Torrentshell and Marmot Essence use proprietary 2.5-layer laminates. The remainder of the models we tested use advanced PU coated fabrics. Marmot's NanoPro PU coating, used in the PreCip, is air permeable; and the light Pertex Shield+ fabric used for the Outdoor Research Helium II is more breathable than most PU coated fabrics. The budget-friendly Columbia and The North Face models use a PU coating as well.
Two-layer jackets are at the low end of the cost continuum. A hanging mesh liner protects the outer fabric of these three jackets and none have pit zips for ventilation. These jackets are best suited for around-town use, and lack the ventilation necessary for high energy activity. All perform best in cool to cold weather, are great jackets if your budget is less than $100, and they handle occasional hikes and short trips just fine.
Models in this category include:
Columbia Watertight II
Standard 2.5-Layer Jackets
In a lot of ways, 2.5-layer technology is what defines the rain jacket category. These models are lighter, more compact, and generally less expensive than the more durable three-layer hardshells. The Torrentshell and Minimalist utilize a laminated fabric, while the PreCip and Venture are built with a coated fabric. These standard jackets are the most featured we tested; all have pit zips for ventilation. They are also the most versatile models we tested; the ventilation makes them appropriate for warm weather use and high energy activity that generates lots of sweat. Sized appropriately for insulating layers underneath, they perform exceptionally in cool to cold weather. The PreCip won our Best Buy award, delivering the most bang for your buck. The Torrentshell, with its helmet-friendly hood, is a great choice for climbing and peak bagging. The Minimalist is the most durable model we tested for those less concerned about weight, and the ventilation features of the Foray earned it a Top Pick.
Models in this category include:
Outdoor Research Foray
The North Face Venture
Ultralight 2.5-Layer Jackets
These bare bones jackets are designed primarily to be super light, forgoing hand pockets and most ventilation features. They excel during high energy activities and all three have reflective logos and patches, a great feature for running and biking. These models are best suited to very active pursuits in cool to cold weather. The ultralight weight and small packed sized makes these perfect just-in-case rain protection as well. The Minimalist and Helium II both use Pertex Shield+ coated fabric, a very light and breathable option. The Editors' Choice winning Essence is built with Marmot's new NanoPro coating, an air-permeable option that breathes unlike any other fabric we tested.
Models in this category include:
Outdoor Research Helium II
Hardshells aka Three-Layer Jackets
These jackets are more durable and often much more expensive. Hardshell jackets are generally heavier than rain jackets due to thicker face fabrics and burly features, but the lines are blurred; many three-layer shells are weighing in quite light these days. The laminated fabrics used in hardshells represent the top of the line waterproof/breathable technology available. Hardshells are primarily designed for the rigors of alpine and winter climbing and their features and durability reflect this.
Sizing your Jacket
Do you want your rain jacket to fit snugly or hang loose? Having a loose fitting jacket gives you more room for insulation and base layers, but does it perform better one way or the other? A snug fitting jacket will maximize breathability, that is the transfer of water through the fabric away from your body. As discussed above, water vapor always wants to move from warm to cool. A snug fitting jacket will create a more uniform warm environment inside that promotes breathability. A loose fitting jacket better promotes ventilation. Pit zips, pocket vents, open wrist cuffs these all move more air when a loose fitting jacket moves as you move.
Care & Cleaning of Rain Jackets
A well cared for and clean jacket will function better and last longer than a neglected, dirty one. First off, be kind to your jacket. Whether you stuff the jacket into its pocket or roll it away into its hood, you will prolong the performance of the DWR treatment. The less abrasion and abuse the face fabric receives, the better. Adopt this habit when stowing your jacket in your pack. Your jacket will maintain its breathability longer as well because the interior stays cleaner and the pores in the fabric stay unclogged.
Eventually, you will want to wash your jacket. Done correctly, washing and drying can have a miraculous effect restoring DWR and breathability. These jackets all can be washed in the washer. A front-load machine without a center agitator is best. All fabrics with a DWR treatment should be washed in cold or warm water using a small amount of powdered detergent. Find the manufacturers recommendation on either the jacket's label or website, and follow it. Cold water and the delicate cycle is your best bet if you have any doubts. Liquid detergents and fabric softeners should be avoided, as they have components that adhere to the fabric's fibers. Choose a double rinse cycle to remove as much soap residue as possible.
Now you have a clean jacket. Any oils, dirt, and grime soiling and clogging up the waterproof/breathable layer will have been washed away and the original breathability should be restored. Now comes the important bit. Hanging or laying your jacket to air dry is the safest technique. A freshly laundered, air dried jacket will sometimes restore a DWR that was losing its ability to bead water. Carefully applying heat can work wonders when cleaning alone doesn't restore DWR. A dryer's low heat setting is the place to start. Again, the manufacturer's care instructions should be consulted. A popular but more risky technique is using an iron, either on low heat or low steam. If the polymers that make up the DWR haven't worn off the face fabric completely, the dryer or iron can make them bead water like a champ again.
After enough use, it will be necessary to reapply a DWR treatment to your jacket's exterior. Spray-on and wash-in treatments are available. Two-layer jackets with a mesh liner should only be treated with a spray-on product, you want the mesh liner to continue to absorb sweat and get it moving towards the outside. Either is appropriate for a 2.5-layer jacket, but we prefer spray-on products.
Here is the advanced technique for spray-on application. Wash your jacket as described above and let it air dry. Briefly place the jacket in the dryer on low heat, until all the fabric is nice and warm. Remove from dryer, hang, and immediately spray on your new DWR. Use less rather than more spray-on product, and with a hair dryer you've readied, accelerate the drying of the new DWR. This technique serves to both restore the original DWR that remains on the jacket and maximize the bonding of the new polymers you are applying. Nikwax and Granger both produce a full line of fabric treatments, including spray-on and wash-in varieties.
The world changed for waterproof clothing in 1976 when W.L. Gore and Associates introduced Gore-Tex fabrics to the market. Gore discovered and patented the process for creating ePTFE, or expanded Polytetrafluoroethylene. This thin film contains millions of small pores, too small for liquid water, but large enough for water vapor to pass through. Laminate this thin membrane to a synthetic face fabric and voila!! the first waterproof and breathable fabrics. Today's waterproof/breathable layered fabrics include face fabrics that are laminated to membranes like Gore-Tex and face fabrics that are coated.
Gore-Tex rainwear quickly conquered the market or, in one sense, created the waterproof/breathable market. Competing waterproof fabrics coated with Polyurethane (PU) or Polyvinylchloride (PVC) couldn't compete. The first Gore-Tex fabrics were 2-layer construction; the ePTFE membrane laminated to a nylon or polyester face fabric and a mesh or thin fabric liner hung inside this layered fabric to protect it and provide comfort next to your skin. Gore quickly discovered the ePTFE membrane's pores could easily become clogged with oils and dirt though, and added another layer to the laminated sandwich, covering the ePTFE membrane with an oil resistant PU layer. This PU layer protects the pores from contamination, but stops all airflow through the membrane's pores. Three-layer construction was the next big advance and mesh or scrim was laminated to the interior of the layered fabric. This innermost layer protects the membrane and provides better transfer of water through to the outside. As the "light is right" ethos took over the outdoor world in the 90s, 2.5-layer technology did as well. This construction incorporates, instead of laminated mesh, a texturized "half layer" printed on the inner face of the layered sandwich.
So does traditional Gore-Tex breathe? No, in the sense that air does not pass through. Yes, in the sense that liquid water passes through the inner most PU layer, and then is wicked to the face fabric through the ePTFE's pores, where it evaporates. This wicking process works best with a large temperature gradient. Water always wants to move from warmer to colder zones. A fabric that does a great job "breathing" when it's cool outside, will not wick nearly as much sweat away from your body when it's hot out.
Gore's original patents for ePTFE expired in the mid 90s, and competitors, many of whom had been developing PU membranes and advanced PU coatings began to experiment with PTFE technology. Options multiplied for manufacturers of outdoor performance clothing, but Gore-Tex has maintained its dominating market share for high-end waterproof/breathable fabrics. Polartec NeoShell, eVent, and Mountain Hardwear's Dry.Q are the latest ePTFE laminates. None of these technologies uses a PU layer, and as a result all are air permeable. High performing PU membranes are popular today as well, examples include Patagonia's H2No and Marmot's air permeable NanoPro laminate. As these newer, truly breathable, or air permeable, membranes gain traction, Gore has gotten on board as well. Gore's latest version of Gore-Tex Pro is its first to eliminate the PU layer, creating the first air permeable Gore-Tex fabric. In our review of hardshell jackets, you'll find jackets intended for serious mountain activities, constructed with these advanced three-layer laminates.
Here is a good summary of many of the top of the line waterproof/breathable fabrics. Marmot's new NanoPro fabrics are rightly garnering much attention. Here is a good article comparing NanoPro to the new air permeable Gore-Tex Pro. For those of you interested in the history of Gore-Tex, and how W.L. Gore revolutionized the outerwear market, and perhaps discouraged further innovation, read Insane in the Membraine.