How much waterproofing do you really need in a jacket or pants, and what factors affect how waterproof your jacket will be?
When people picture high-end outerwear, they’re thinking of jackets with a waterproof breathable membrane. If you’re really getting after it and expect some nasty weather, then this is what you want. Note that we’re not talking about heavy-duty coated garments like foul-weather gear for sailing; the PVC coating on this may be great for keeping the wet stuff out but it makes this jackets and pants heavy, and you’ll be sweating buckets if you’re moving around at all.
The OG waterproof breathable technology utilizing a membrane is Gore-Tex, which is licensed by many manufacturers for the creation of waterproof/breathable outerwear. Many vendors also utilize their own proprietary technology based on the same idea, including The North Face (HyVent), Columbia (Omni-Tech), Marmot (MemBrain and PreCip), Mountain Hardwear (Dry.Q), Spyder (Xt.L), and Patagonia (H2No), to name a few.
For purposes of illustration, we’ll talk about how Gore-Tex works, but you can pretty much apply the same idea to all of the above. There are some differences in execution, but the general concept is the same.
At the heart of the Gore-Tex fabric is an extremely thin membrane with over nine billion pores per square inch (as shown to the right between the two fabrics). These microscopic pores are 20,000 times smaller than a water droplet, so they don’t allow water to pass through. At the same time, they’re also 700 times larger than a water vapor molecule, so when you start to warm up and release water vapor, it’s not trapped under the garment. That’s what is referred to as breathability. The membrane is also windproof, so chilly breezes won’t drive you indoors.
This membrane is bonded to a textile to create a Gore-Tex laminate. Several different constructions can be used; the most common are two-layer (2L) construction, where the membrane is bonded to just the face fabric (and the liner fabric ‘hangs’ between you and the membrane), and three-layer (3L) construction, where a backer fabric is bonded to the other side of the membrane as well.
All waterproof breathable garments have a second aspect, the DWR (durable water-repellent) treatment on the outer face fabric. It consists of a polymer applied to the fabric that water bead up and roll off, so it’s less likely soak in and try to force its way to the interior of the garment.
It’s important to note that there are many jackets and coats out there with only a DWR coating and no additional membrane or laminate. These are helpful for repelling very light mist or snow for a short period of time, but they can be quickly overwhelmed by heavy rain and become saturated.
DWR coating can be re-applied by the user with either wash-in or spray-on products. This should be done when your garment gets worn and water no longer beads up.
Read more about how DWR technology works: DWR Decoded
You’ll usually see both a waterproof rating and a breathability rating in most product descriptions for outerwear; which you select will depend on the conditions you expect to face and the uses you’ll put your outerwear to. For reference, standard Gore-Tex has a waterproof rating of 28,000mm and a breathability rating of 17,000mm/g2.
Waterproof Ratings: Saying that something is waterproof is a lot like saying that something is heavy. Everything is relative. Waterproof enough for Utah may not even come close to keeping you dry in Washington. To make things even more complicated, many manufacturers use different rating systems, which makes it hard to compare one jacket to another. Most, however, use a measure of the millimeters of rain a jacket could withstand without letting water in.
Breathability Ratings: Breathability ratings measure who much sweat vapor can escape through a square meter of fabric in 24 hours. Even the best hardshell jacket will get a bit clammy if you’re working hard enough, but as with waterproof ratings, things generally get more comfortable as the numbers get higher.
One thing to be clear on is that breathability and ventilation are very different things. Underarm zippers and vents are great for staying cool, but have to obvious disadvantage of allowing the elements in. That being said, here’s a short breakdown of breathability ratings:
Seam Taping: Seam taping is exactly what it sounds like. When the jacket is built, a waterproof tape is applied over the top of the seams to keep water from leaking through. There are several different types of taping, including welded seams, but they all fall into three basic levels of protection. Like waterproof ratings, what works fine in one region may not be sufficient in another.