What Does Waterproof Breathable Mean?

"Waterproof Breathable"

Is that Waterproof AND Breathable or is it Waterproof OR Breathable?

Gore-Tex, Neo Shell, eVent and other waterproof membranes are funny things. For many people it's the layer they reach for anytime the weather isn't perfect. The thing is that those waterproof breathable membranes just don't seem to breathe very well when it's wet out and as far as I can tell, nothing does. The problem is physics.

Okay, so I talked about membranes, what are those? There's two classes of waterproof jacket out there - membranes and coatings. Membranes work by bonding a membrane to an outer material (and often another layer or two) while coatings are just that - something basically slathered onto the outer material with maybe a protective layer or raised profile on the inside. Membranes - like Gore-Tex and eVent tend to breathe better, but the jackets also tend to be heavier, less packable and more expensive. Coatings - like Marmot's NanoPro or Pertex Shield+ are lighter, less expensive, but less breathable and often less durable that their membrane counterparts.

The Waterproof Breathable Problem

Waterproof breathable membranes and coatings work on the principle of diffusion. Diffusion needs a difference in humidity on each side of the membrane in order for your jacket to accomplish anything. The bigger the difference, the higher the rate of diffusion. When you are working hard, it's wet inside your jacket, so it's best at moving that sweat to outside your jacket when it's dry out.

Pissing rain means it's pretty damn humid out - which means the driving pressure for diffusion is low or straight up zero which means maybe your jacket is waterproof, but it just isn't very breathable. If you are sweating while it's pouring raining, you're getting wet. If the humidity outside your jacket is the same as the humidity inside your jacket - then there's just nowhere for your sweat to go, so unless there's some crazy voodoo going on that I don't know about, I don't know how a breathable jacket could keep you dry while you are working hard in a humid environment. It's certainly what I've experienced during my time in the super wet coast mountains of BC.

If you want more info on how waterproof breathable membranes and coatings work, REI has a really good article on it.

What it really comes down to, is if it's raining out, you have three realistic options:

Say screw it to a shell, get wet from rain. Works when it's warm.
Wear a waterproof shell, work hard and get wet from sweat which is generally warmer than getting wet from the rain, but you freeze when you stop.
Wear a waterproof shell , realize that it's going to breathe like shit, even if you have the fanciest thing out there because the humidity inside and outside the jacket are so similar and restrict yourself to only going as fast as you can go without seriously sweating. If you start getting wet, slow down.

Notice that there's no solution for 'stay dry while working hard in the rain'. There just isn't anything out there that can do that at this point.

Despite on and off pissing rain and freezing temperatures, I used a simple wind layer when running the Glacier Grind Ultra - no waterproof jacket is going to keep you dry in that weather and at least the wind shell would dry faster when the rain gav… — Despite on and off pissing rain and freezing temperatures, I used a simple wind layer when running the Glacier Grind Ultra - no waterproof jacket is going to keep you dry in that weather and at least the wind shell would dry faster when the rain gave us a break.

Now, there are cases where waterproof breathable shells have advantages. Take ski touring for example. You might ditch that hard shell on the skin up, but on the way down, it'll shed snow beautifully.

There's a couple of issues with that last statement though.

First, you often end up needing to ditch the shell on the way up because even in dry conditions, you likely sweat too much going up hill to stay dry (though the latest membranes are getting pretty good if you aren't a heavy sweater).

If there's wind and you're headed uphill, you need some sort of wind layer like the Patagonia Houdini or the Arcteryx Squamish Hoody/Incendo Hoody siblings. That's not too bad though because those wind shells are way more breathable than a waterproof breathable shell anyway. Hold onto that idea - if you're working hard going uphill and it's windy out, you're probably going to need to carry an extra jacket to handle the wind when your waterproof breathable layer can't keep up with moving moisture.

Skyler crushing it uphill - in this case he was bootpacking up hill in the Westcomb Switch Hoody.

The real reason to carry that waterproof-breathable jacket on a ski tour is for the way down - protection from snow while you're skiing - but do you really need to pay for the most breathable possible jacket to get that done?

The Alternative Solutions

I have a different way of doing things. In fact, I have two. The first is 'the two jacket system' and the second I call 'the honest compromise'.

I'm going to reference gear that's currently in the review-cue since I've got it lying around and have used it recently, but there's lots of options to everything.

The Two Jacket System

The two jacket system basically breaks the goal of your shells down into component parts - instead of using a jacket that is decent (at best) at everything, let's use one jacket that's super breathable and one that's waterproof.

This is the system I use in the summer for climbing, scrambling and general mountain fun.

The Breathable Jacket

There are some amazing wind shells out there. These things shrug off wind and even light rain thanks to DWR coatings. I've used the Patagonia Houdini and the Arcteryx Incendo recently and they're both featherweights that disappear into your pack and breath miles better than any waterproof breathable jacket out there that I've tried. They even handle short bouts of light rain without too much complaint.

Matt, rocking the Arc'teryx Squamish Hoody to cut the wind. He's actually the one who first convinced me to switch to wind layers for most activities.

These are actually my go-to layers for most activities in the mountains. If it's not currently raining, then I care a lot more about breathability than being protected from a problem that doesn't currently exist.

If I'm half way up a mountain and it starts to rain though, then I need something waterproof.

The Waterproof Jacket

So, it's started pissing rain half way up a route, what do I do? I stash the windshell and I pull out my waterproof jacket. There's a ton of light, coatings based waterproof jackets out there and a lot of them are way cheaper than membrane-based waterproof breathable jackets. Light and cheap. I like it.

Freezing rain on Mount Assiniboine was just a joyous day. We were wearing waterproof breathable jackets to stay dry, but that meant our pace was determined by the speed we could go without sweating.

I'm currently reviewing the Outdoor Research Helium II. While breathable, it's not as breathable as a membrane jacket, but it IS just as waterproof. If it's currently raining, then how breathable something is really doesn't matter that much because nothing is getting past the simple fact that the humidity inside and outside my jacket is the same damn thing so just as much moisture is diffusing IN to my jacket as OUT.

Now, nothing says you can't bring a membrane jacket and if the humidity isn't 100% and it's only a light drizzle, then yea, the membrane jacket is going to be more breathable, but the difference just isn't that big and some of the coating jackets are way lighter and pack way smaller. The extra size and weight for a membrane jacket may not be worth it.

The Two Jacket Bottom Line

By giving up on the idea of one jacket doing everything and going with two jackets - I have a breathable jacket when I need a breathable jacket and I have a waterproof jacket when I need a waterproof jacket. The real kicker is that the two jackets combined can be lighter and cheaper than a single membrane based waterproof breathable jacket.

The Arc'teryx Beta AR jacket is basically the standard against which all other waterproof breathable jackets are measured. It's light at 460g advertised weight and uses the latest Gore-Tex Pro membrane, but it's also expensive at an eye-watering $700CAD. You can save some money by going with the MEC Synergy jacket at 438g and $425CAD.

My current Two Jacket system uses the Patagonia Houdini as a wind layer that clocks in at a measly 102g advertised weight and despite being made by 'Pata-gucci' only costs $119CAD. For a waterproof layer, I'm currently trying the Outdoor Research Helium 2. As you'll see in the upcoming review, it happily keeps me dry, it's breathable enough that I don't need to immediately switch layers when the rain stops, comes in at a super light 180g advertised weight and only costs $220CAD.

The traditional waterproof breathable system clocks in at 460g and $700CAD on the high end and 438g and $425CAD on the low end. In comparison, the two jacket system is going to cost you in the neighbourhood of $340CAD and weighs 282g.

It's counter intuitive, but by going with two jackets, you ca save money, you can save weight and you can save space in your pack.

Even if you just can't wrap your head around the idea of leaving your trusty Gore-Tex jacket at home, being willing to leave it in your pack until it's genuinely raining and using a lightweight wind shell when it isn't is going to make you more comfortable for any reasonably high output activity.

The Honest Compromise System

The Honest Compromise System is designed for the needs of winter mountaineers. It's a system that I've wanted to see for ages and thanks to the dead bird people, it's starting to be a real thing.

A caveat: this system really only works in the winter. Once you're dealing with actual rain, it's time for the two jacket system.

When you're ski touring, you need something that's breathable on the way up and waterproof. The thing is, your shell doesn't need to be waterproof everywhere. Snow doesn't settle on vertical surfaces the way rain does - so what you really want is a jacket that has waterproof shoulders and arms, but is super breathable elsewhere. Likewise for pants, a waterproof butt and lower legs is really nice, but most other places, breathable is what you really need.

This brings us to the honest compromise. I spent this ski season rocking the Arc'teryx Procline Comp jacket and I used the Lythic Comp pants for a couple of seasons. It strategically balances waterproof panels of Gore-Tex Pro where you need waterproof and a super breathable, and stretchy softshell where you don't.

Katherine climbing in an 'honest compromise' jacket - the Arc'teryx Alpha Comp. The lighter blue areas are softshell.

The result is pretty awesome and I really like this as a solution for higher output winter activities.

The Honest Compromise Bottom Line

With the honest compromise jackets you have a shell that breathes enough that in cooler weather at least, you don't need to strip off your shell on the way up and is waterproof where you need protection from snow. It's not suitable for rain, because that'll soak through the softshell panels, but in the winter it's pretty ideal. I've also used these compromise shells for ice climbing and they're pretty solid there too.

The rub, is that the jacket still isn't breathable enough for spring touring, you still need to use a wind layer if it isn't cold enough to keep your sweating at least a little bit in check. If it's a nice spring day with blazing sun and my main concern is wind, I'm still going with a wind shell, but for those mid-season days when it's puking snow and pretty crisp out, these are the one jacket solution.

They are an honest compromise - they trade 'waterproof' for breathable because you just don't need 100% waterproof most of the time in the winter and the result is better because of that honesty. I really hope other brands jump on this trend.

The Waterproof Breathable Reality

I worked in retail for years and in that time I could not count the number of people who brought in a brand new Gore-Tex jacket and told me it was defective because they got wet while wearing it in the rain. The jacket was waterproof - but because there wasn't enough of a difference in moisture on each side of the membrane, the diffusion required to keep that person dry from sweat just wasn't there.

For low energy output activities like light hiking - you can get away with a single waterproof breathable jacket. For high energy output activities like ski touring, a waterproof breathable jacket just isn't going to breathe well enough for most people. If rain isn't actually a worry, then be honest about that and ditch the waterproof and go with breathable with strategic regions of waterproof. If rain IS a worry, then either go slow, or get wet.