Waterproof/Breathable Shells – the breathability issue

The importance of staying dry particularly resonates with me after fulfilling a lifelong goal Friday night by attending the famed Lebowski Fest, but that’s another story. I’d planned to write about what shell fabric is best for a belay parka (IMO, a non-waterproof shell is better for most belay parkas – will explain later). But then, aw heck, I got to rambling – too many White Russians and Oat Sodas still in my blood stream, I guess. So, well, you know, like, there’s a lot of ins, a lotta outs, a lot of what-have-yous here. Regarding shell materials, for now I’ll just do an overview of waterproof/breathable fabrics (aka “Hard Shells”), more geared toward understanding breathability as it

At least he didn't pee on it.

applies to field use. Maybe it’ll help understand things like which works better if Wu pees on your rug (and they pee on your fucking rug!).

Waterproof shells do, at least mostly, block incoming moisture (some leak sometimes). They do this by sandwiching a thin barrier, a film, also called a laminate, between the shell fabric and the lining. The laminate itself is too fragile to stand alone, and is super thin, this stretchy white thing that’s waterproof and breathable. So how come you sometimes feel wet when being active in a hard shell?

Most often, the problem comes from the moisture you produce, making you wet from the inside. When you move, you generate heat. Moisture comes with it – by-products of energy metabolism (higher work output = higher energy turnover, a.k.a. greater metabolic output), as we all recall from physiology class, include heat, H20 and CO2. The CO2 and H20 get released a couple of ways, primarily through the mouths of many – if you don’t believe me, just visit your local Wal-Mart. The mouthbreather species abounds everywhere, though, as I’m sadly reminded of when I get busted watching Cops reruns. But those are extreme examples to illustrate a point. Another way H20 gets released is through our skin – i.e. water vapor and sweat – even if we don’t visibly notice it, because at low work rates (and in dry environments, which greatly enhance evaporative rate) it evaporates before we feel damp. But as long as we’ve got a metabolism – as long as we’re alive – we’re releasing heat, H20 and CO2. Just at varying rates, depending on what we’re doing. The moisture has to escape to the outside environment or we get wet from the inside. You can test this by putting a non-breathable plastic bag over your head and going for a run. The inside of the bag will be warm and wet. Warm for awhile, anyway.

OK, so the flipside to waterproof shells is the “breathable” part – in quotes because it’s far from real-world effective. Companies all claim their fabrics breathe, and, sure, they breathe well at certain rates of output. It’s why the masses love them – riding a lift up, then skiing down, or walking to the coffee shop in the rain, simply does not push any realms of breathability. Cool. It works great for certain applications. But anybody working hard can quickly overwhelm the breathability limits of waterproof/breathable fabrics – in other words, your moisture output becomes too much for the fabric to keep pace – remember that H20 and CO2 are by-products of hard work (increased metabolism, or energy turnover). Then, the moisture can’t escape fast enough through the waterproof/breathable barrier, and the inside of your shell gets wet with sweat. Cute lab tests concocted to show breathability are cool (kewl if you’re cool, so I’m told…) and work great in a gear shop’s display or an exhibitor’s booth at a trade show. Simulclimbing like mad, or post-holing like an elk on an approach, though? Ha, breathability, right. (Ha, leads…)

The fact remains that with current technologies, making something fully impermeable from the outside also compromises its breathability from the inside – ya can’t have it both ways. Not yet. Some companies have made notable improvements, though, including some cool things I’ve tested, but that I can’t talk about yet lest I end up in Guantanamo Bay.

It sounds like I’m bashing hard shells, but, actually, I use them a lot. On some climbs, protection is my paramount concern, and indeed hard shells offer superior protection. They’ve got some other advantages, too, which I’ll hit on soon, along with things to consider regarding making them work for you. As with so many things, it’s a balance – in this case, between which is more important for the situation, keeping dry from the outside, or from the inside?

14 thoughts on “Waterproof/Breathable Shells – the breathability issue

  1. I think the membrane issue is a pretty straightforward physics problem. You set up a diffusion gradient which will always work better when it’s warm and wet inside and dry outside. But if it’s dry outside why are you wearing a hardshell? It seems to me that the DWR is the key to the whole system. If you can bead that rain up on the outside you leave much more fabric dry so that your sweat can pass through. As soon as that outer fabric wets out you basically shut down the diffusion. In my opinion, clothing makers would be better off focusing on either the DWR or some other hi-tech fibers that resist wetting to begin with. And a good DWR/fabric combo would be great for softshells too. And maybe it’s just me, but even with the official tech-wash detergent I don’t get anywhere near the claimed DWR life before I have to reapply some. Maybe that works in the lab when there’s no pack involved.

  2. Great article KC. I still prefer soft shells. I tried with two soft shells (one on top of the other) once and it added a lot of waterproofness while keeping me somewhat drier from the inside (drier than a hardshell), but like all soft shell, eventually it overflowed the DWR and I ended up soaked.
    As for belay parkas… what about the DAS or the micro puff, or the Nano. how waterroof are they? the Nano seems waterproof enough for the rain in new england…

  3. great comments already — Steve, yeah, agreed, the DWR thing is huge. without that, it doesn’t matter what you have, it’ll be saturated, then no gradient. so key, and not everyone realizes it. makes me realize i should have noted that in this post — so thank you! i notice the same thing, in that the home-applied DWRs never seem as good. when new, a good DWR is golden. but they do wear easily, just through normal use, and certainly from abrasion and rubbing. one thing that clothing manufacturers (at least the ones i work with) consider is how well various fabrics “hold” a DWR. things with textile textures and subtleties i don’t understand can greatly affect how well a fabric holds its DWR.

    Aaron, the link isn’t working! let me guess — an umbrella? and if so, guess #2 — you live in the PNW or the UK? when i guided in the Cascades one summer, forever ago, an umbrella was fully part of the kit. ya’d be out there with clients, and have the umbrella affixed to your pack. crucial equipment!

    Uri, I’ve done that double soft shell system myself, and quite like it — granted, it’s much drier here in CO (er, I mean, the ‘Rado). Did Patag’s Alpine Wind Shirt, and had the Houdini as well. Used the former on the approach, and put the latter on for the climbing. but indeed that seems the problem with so many soft shells, is that they wet out. some dry fast, though, but it’s tough once you’re really soaked. as Steve said, that DWR is key. i’ve been testing some hard shells with greater breathability (seems to me), and i wonder if that might be the way forward — if the laminate blocks it from the outside, but does better with the breathability than previous hardshells… then again, the DWR thing is really key. hmmm.
    those belay parkas are not waterproof, but come with a good — guess — a good DWR. and the primaloft insulation in those ones you mention does a great job of staying hydrophobic, too. there is a waterproof-shelled Nano coming out next fall, though. i was going to write about shell materials in this post, but then got sidetracked. will try to do that soon!

    • Yeah.. I was wondering that myself. Like Steve said, if you apply the DWR after the original starts wearing off it’s not the same.
      Kelly? Any insight on this?

  4. Yeah, that’s interesting. I dabbled in pacifism myself once… not in Nam of course.

    While we’re all spewing the dreaded gear talk: Kelly, I noticed you’re video description of the new M10 Jacket. Waterproof, breathable, 10 ounces, sick! $400 – while there’s the Marmot Mica and the new OR Helium at 7-8 ounces, breathable, and waterproof at $130. What are the advantages of the M10 over a lighter and cheaper jacket?

    • Sorry for the delay, Kevin — I was bowlin’. So I had no idea what the dude said.
      Those other jackets — I did not know that. Ahem, OK then. Uh-oh, gonna have to find that video, hope they got my good side.
      I have been a huge fan of the M10, but indeed, huge price diff vs what you’re comparing ’em to. I’m not very familiar with those ones, but at quick look, the biggest difference appears to be that they’re more of the “emergency” rainshell type pieces — not a bad thing at all, as I blather about in reply to Steve, below. They’re 2.5-layer shells, vs the M10 being a 3-layer. I got to thinking, after your comment, that I’ll compose a post on the differences, and what’s better for what (so, thank you!). But, briefly, a 2.5 isn’t as durable, but is lighter, usually isn’t as comfortable, more prone to contamination of the membrane as well. But if it’s just for emergency use, this isn’t such a big deal. For certain apps, these are great (and, IMO, Patagonia is lacking in this style of ultralight 2.5L right now — we had a Spectre pullover, which was rad for this! But it got dropped. There’s a sweet similar pullover in the works, forget when it’s due out).

      The 3L shell is usually more breathable, feels better, more durable, etc — so more of an all-use type high-end shell. A good 3L shell is usually heavier. The M10 pulled off the bennies of a good 3L with the weight of many 2.5L’s out there. It’s super sweet for sure. But indeed, ya pay for it. Probably a more appropriate comparison of the M10, at quick look, would be to OR’s Mentor ($425, but 17 oz) rather than their Helium. Different beasts, really.

      Hope that helps some.

      Funnier way of putting it, which I’ll paste here purely for entertainment — one of the Patag guys saw your question and sent me this, in terms seemingly tailored for me:
      “The Mica/Helium are beergarita grade: 2 parts Cuervo, 2 parts Tecate and 1 part frozen limeade — you might mix it if you just need tequila mixed with somethin to hit your lips.

      M10 is a full on top-shelf marg mixed with carefully balanced hand squeezed lime juice, fresh squeezed organic oj and whatever else goes into your crazy margs Kelly.”

  5. I’m also searching for the magic DWR application technique. Wash in seems weird – applying a non-water soluble product with water. Spray on has worked just OK for me if I let it air dry then throw it in the hot dryer. Like Kelly says, it just doesn’t seem to last like the factory coating. I need to reapply some to my dragonfly and I was thinking of using a heat gun (industrial hair dryer and very carefully) to really coat that fabric. Like ‘Rado, Idaho (‘Daho?) is a great place for soft shells. If the heat gun would work to turn a kids bargain basement windbreaker into a functional emergency shell for peak bagging/scrambling that could be awesome.

    • Yo Steve from the ‘Daho…let me know if the heat gun works. Indeed, a cheapo windbreaker that’s made waterproof for an emergency shell would be great. I’ve long wanted such a thing, actually — like, don’t even try to make it breathable, just make it like a 2-ounce freakin’ fitted garbage sack with welded seams and a helmet-compatible hood, that you only use if it’s pissing rain. The material Integral Designs uses for their Siltarps, for example — just did a quick look, and they make a SilPoncho, but that thing would be a mess when you’re rapping off something or downclimbing sketchy slabs. Need a climbing cut.

      Anyway, would seem like it could be made fairly cheap. In such cases, any “breathability” would be moot anyway, because the outside is saturated.

      But I think companies run into a marketing problem, in that the people who buy most of the products that keep outdoor companies in business aren’t looking for a superlight emergency shell in which they don’t care or want breathability. And most folks want something that says “breathable” on the label. Otherwise it’s just a raincoat. But I’d love a 2-oz raincoat with a clip-in loop. Would be perfect for summertime alpine thunderstorms.

  6. From ‘Secrets of Warmth’ by Hal Weiss, page 43
    –“The worst thing about breathable systems is that they break down when you need the insulation most- that is, in very cold conditions. In temperatures below 15 degrees F, when the outer layer of clothing becomes about as cold as the external air, very little moisture will be able to get through this layer. Moisture will condense before it gets close to the outermost layer and freeze as it gets closer to it. This creates an impermeable layer of frost…”

    From “The Mountaineering Handbook” by Craig Connally page 232
    –“Wear as little base-layer insulation as possible; you’ll be cooler but your [waterproof/breathable] shell will be warmer, and that makes it move moisture faster.”

    The only DWR I use is one that requires the washing machine. yes, the factory DWR can’t be beat but that’s up there with nikwaxing the leather palms on gloves (redux!!)- part of the gear CCM (constant, care and maintenance)…

  7. Dude, maybe in Colorado most of the moisture comes from inside…but where I live it seems that quite a bit o moisture comes from the outside!

  8. Sorry for my delay here, guys. Ahhh, the DWR thing. Wish I had a good answer. I asked some of the Patagonia folks who source materials, make/design the garments, evaluate them, etc, and nobody had a great recommendation for do-it-yourself DWRs. They acknowledged that none of them seem to work as well as the initial one that comes with the jacket (don’t know why, I’ll try to remember to ask sometime). I wonder if any of it has to do with contamination of the fabric and the wpb membrane over time — apparently that’s huge. Body oils, dirt, etc, somehow break down the effectiveness of the waterproof fabrics, which is unavoidable if you use the shell the way you should. But some maintenance helps.

    One of the guys had some good recommendations here for what Volk, above, referred to as CCM (constant care & maintenance). It’s a bummer that all this high-tech stuff still requires such care, but so it goes. Anyway, from one of the technical product development guys at Patagonia:

    “The key is keep the garments clean from oil and dirt residue over time. Washing tech shells regularly in cold water by hand or gentle wash works well. Then throw the garments into a dryer on low heat (Must keep an eye on them). The heat will reactivate the DWR and is quite effective.

    NikWax does a decent job. TechWash is a great, non-detergent cleaner. TX Direct is their DWR replenisher. I think there is a spray-on for lined shells and a wash-in version for non-lined shells.”

    BTW, I Googled those NikWax products, and there’s a pretty good comment, with the guy’s results, on Amazon. When I went there, it was the top comment, from someone called “B. Christensen”:

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