Clothing & Apparel 101: Waterproof Versus Water-Resistant OuterwearDecember 14th, 2013 By Adam Broderick
Other than injuries and broken equipment, wet weather has always been the quickest way to a ruined outdoor adventure. But it doesn’t have to be.
Staying under the safety of your tent’s rainfly isn’t the only option when a storm rolls in, unless of course all you brought was that beautiful 800-fill down puffy. That jacket may be the warmest garment in your closet, but anyone who’s spent more than ten seconds in one during a torrential downpour knows it will just turn you into a human sponge under those conditions. Thankfully, dragging around more rubber than a dominatrix isn’t the only alternative anymore!
Tahoe Mountain Sports put this waterproof gear guide together to help you navigate the modern plethora of sleeker, lighter, more-comfortable, water-shedding, moisture-wicking, wind-breaking and all-around-adventure-slaying wet-weather gear out there.
Outerwear fabrics these days almost all have some built-in (or coated on) resistance to getting wet, but there’s a big difference between water-resistant or water-repellent and truly waterproof outerwear. Under harsh conditions, water-resistant/repellent quickly translates to absorbent. It won’t take those types of jackets, pants, boots etc. long to become saturated in heavy rain (e.g., the aforementioned puffy).
How Waterproof is It?
Legitimately waterproof means sealed seams, welded or storm-flap-protected zippers and waterproof membranes. These items are rated based on how well they resist the entry of pressurized moisture in a laboratory setting. Most are measured in millimeters, but what the heck do those numbers actually mean?
The “mm rating” of a waterproof garment tells how much rainfall the item can withstand over a 24-hour period without any moisture leaking in. The higher the “mm rating”, the more waterproof the garment is. There are just shy of 305 mm in a foot, so a 20,000 mm waterproofing is pretty darn waterproof (withstanding 64 feet of water in 24 hours). Some garments, however, might also (or instead) provide a “psi rating” (pounds-per-square-inch).
A higher “psi rating” means a garment can handle more pressure. Rainfall can range between 1 and 7 psi. So, why do you see ratings of 25 or even 40? It’s because other forms of pressure can try to squeeze that moisture through the waterproof membranes in your outerwear (e.g., pack weight on your shoulders/back or sitting in the snow). That must be why my butt always gets wet when I’m snowboarding!
Breathable vs. Non-Breathable Outerwear
Okay, now that you’ve calculated the pressure of your bottom, let’s talk about those pits. Non-breathable fabrics are going to be the most bomber of waterproof materials, but that’s not going to help much if you’re moving around a lot.
Look at it this way: Breathable fabrics (e.g., Mountain Hardwear Dry.Q Elite) let moisture move from the inside out, but not from the outside in. Non-breathables don’t let moisture move in either direction. That’s why Old Yellow, your raincoat from the 90’s, keeps you dry until you start exercising, then the inside turns into a steam room.
Breathability is measured by how many grams of water vapor will pass through a square meter of your garment’s fabric, from the inside to outside, in a 24-hour period (g/m2/24 hours). The pores the vapor passes through are thousands of times smaller than a raindrop, which is why something waterproof can also be breathable. Waterproof membranes also usually incorporate materials resistant to oils, like those from your body, sunscreen, etc., that might compromise the waterproofing over time.
In summary, the rubber raincoat you grew up with, or a more stylish modern version made from polyurethane-coated nylon, will always keep you the driest if you are only doing things like hanging outside or walking a short distance to school, the store or across town on an errand-run.
But if you are backpacking through the Sumatran rainforest, jogging in Seattle or backcountry skiing the Sierra Nevada, you’ll want something that is both waterproof and breathable.
Hey, That’s Not Waterproof!
Leather is not fully waterproof, ever. Neither are water-repellent coatings. But many waterproof products do use water-repellent coatings, because the waterproof membrane is usually sandwiched between other layers. This is generally called the DWR or “durable water repellent” coating/finish. Washing your Levis in some Nikwax, however, does not make them a pair of ski pants.
Nikwax is, however, a great way to extend the life of your waterproof garments. You see, your garment’s DWR will wear out before its waterproof membrane does. And if you revitalize it before that happens, the garment lives on. Once the DWR is completely gone, though, there’s no bringing it back. And the rest of that garment is now compromised. But please, read each item’s care instructions before playing Scientist. Then try either NikWax Tech Wash for in-laundry care or NikWax TX Direct for spray-on pre-wash care.
Here are some of our favorite industry-leading waterproof-breathable membranes:
- The North Face HyVent
- Helly Hansen Helly Tech
- PolarTec NeoShell
- Marmot PreCip and Marmot MemBrain
- Mountain Hardwear Dry.Q Elite
- Gore-Tex (used in many brands)
- eVent Fabrics (used in many brands)