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
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?