Waterproof/Breathable: What Does It Really Mean?
Ironically enough, the definition of waterproof/breathable is anything but cut and dried. For active hikers, runners, cyclists, and climbers, protection from rain and wind is only half the battle.
At Eastern Mountain Sports, we have access to outdoor athletes, product designers, and store staff. We asked them the same questions to find out what waterproof/breathable means to them and how they keep themselves dry when the weather is anything but. What we found was a number of viewpoints with different perspectives-and not all see eye to eye.
Question 1: What does waterproof mean? Are all waterproof garments waterproof to the same degree?
Waterproof is supposed to mean “water-PROOF,” not “water-resistant.” You should be able to stand there in a downpour with a smug look on your face, aware of the pounding precipitation solely via your senses of sight and hearing, not feeling. ~ Charlie Townsend, Climbing School Manager, Eastern Mountain Sports
“Waterproof” in the outdoor industry technically means one thing—the fabric does not allow water to seep through it at a pressure of at least 5000 mm of water in a static-column test. In this test, a tube is placed on a piece of waterproof fabric and filled with water. The jacket is considered waterproof if no leakage occurs when the tube contains 5000 mm of water. While “waterproof” sounds like an absolute term, in the outdoor industry, it’s not; it’s more of a spectrum. ~ Chris Vachon, Store Manager, Eastern Mountain Sports, Peterborough, NH
Regarding garments, waterproof essentially means that water will not pass through under a set of predetermined conditions. These conditions will vary, but it is a wise consumer who chooses waterproof outerwear from a company that adheres to the highest standards. Reputable companies like Marmot or Gore-Tex produce or fabricate gear using the highest-quality fabric that meets the highest possible standards of waterproofness and breathability. You get what you pay for—there’s nothing like being soaked and freezing a day from the trailhead and thinking, “I’m glad I saved $100 on this budget outerwear...” ~ Pete Takeda, Marmot Sponsored Athlete
Waterproof means water droplets cannot pass through. The degree to which the garment is waterproof varies according to the waterproof coating/lamination, design, garment making and construction, etc. Not all garments have the same degree of waterproofness. ~ Simon Chui, Outerwear Sourcing Specialist, Eastern Mountain Sports
Waterproof means impervious to water. While there are different testing methods used to measure waterproofness, waterproof is an absolute. You can't make something more waterproof than waterproof. ~ Fielding Miller, Backbone Media
Waterproof means repelling water. Some are more waterproof than others.~ Stacey Kawecki, Meteorologist, Mount Washington Observatory ---My understanding is that waterproof means that no water will make its way inside that layer. But not all waterproof clothing is the same, in my experience. Some waterproof clothing has just a spray-on that repels water for a length of time, but if it wears off, it can become easier for water to penetrate. Other garments are like plastic bags that don't breathe or can spring leaks. Materials like Gore-Tex, with a spray-on on the outside, I find, work the best. They are breathable, but repel the outside water. ~ Ryan Knapp, Mount Meteorologist, Washington Observatory.
Question #2: Regarding rainwear, why is breathability important?
A waterproof, breathable garment is really a Houdini act. It keeps moisture from coming in, while allowing it to escape out. But there are limits. If you are really working hard and generating a lot of heat, you are still going to generate a lot of sweat, because the jacket is also keeping you warmer. That is why having the ability to adjust your temperature through the use of pit-zips and such is so important. If you’re working hard to get up that mountain, ask yourself if you are overdressed for your current exertion rate. If the answer is yes, don’t wait. Open up those pit-zips and let off the steam now before you get too sweaty. Wearing layers that also up-zip can be the silver bullet you need, because who wants to stop along the side of the trail in a deluge and take off layers? Remember, the key is to not wait until you soak your clothes with sweat; then it can be too late, and you had better be hoping you're at least wearing a wool base layer. ~ Jen Shultis, Adventure Racer
Without breathability, there's no real reason to have raingear in the first place, as you will end up just as wet. And, if you're going to get wet, wouldn't you rather have that wetness be from some fresh source like actual rain, rather than some slime that your body miraculously vaporized and pumped out through your pores, just so you could smear it all over yourself again? No, thanks. ~ Charlie Townsend, Climbing School Manager, Eastern Mountain Sports
If the rainwear doesn't breathe, that means moisture from your body will build up in between the rainwear and your body. And finally, your body will get wet and overheated. ~ Simon Chui, Outerwear Sourcing Specialist, Eastern Mountain Sports
Breathability is big when it comes to rainwear because this gear is often worn when it is warmer out, meaning that the body will have a need to get rid of heat during strenuous activities (hiking, running, etc.). At the same time, it is important to cover the body and keep it dry, so breathability is important to be able to both exhaust heat and stay dry at the same time. ~ Brian Clark, Meteorologist, Mount Washington Observatory
It allows one's sweat in the form of vapor to exit the garment. This is important because even if moisture does not enter from the outside, it is equally important that it does not remain trapped on the inside. ~ Mike Finnegan, Observer, Mount Washington Observatory
While it’s easy to expect waterproof/breathable outerwear to solve all your foul-weather challenges straight off the rack, it’s important to realize that staying dry when you’re standing still and staying dry when you’re active are two very different things. Air temperature, the intensity level of your activity, and your body’s tendencies to run hot or cold all affect how you select your supporting cast of base layers and ventilation features. By managing all the factors our panelists mentioned and investing in quality waterproof/breathable gear, you can protect yourself from the uncomfortable (and potentially dangerous) effects of precipitation and perspiration, and have more fun in the rain.