[Editor’s Note: This is a follow up to our Outerwear 101 piece. If you haven’t read the 101 article yet, you might want to start there. It’s an outstanding overview of outerwear technology and applications, and a good read for anyone who uses technical outerwear.]
The Old Paradigm
Outerwear technology isn’t the sexiest topic in the ski industry—it’s more fun to compare the specs on your new skis with your buddies than the specs of your new jacket.
But that may not be true for long. The outerwear industry is undergoing its first serious paradigm shift since the 1970s, when Gore-Tex founder, Bob Gore, invented waterproof / breathable fabrics (“WPB”).
Over the past 40 years, we saw skis get shorter, then shaped, then fat, then rockered, then tapered. Ski boots went plastic, lost their laces, lost their buckles, re-gained their buckles, got taller, got shorter, then got tall-ish again.
Outerwear pretty much stayed the same.
Sure, there have been a few notable advances in outerwear technology in the past 45 years—primarily 3L fabrics, waterproof zippers, and seam welding—but none that changed the game as radically as, for example, fat skis have.
Today, however, outerwear technology is finally getting some attention, thanks to the invention of air permeable fabrics (“air perms”). These WPBs allow a very small amount of air to flow through them, which in theory greatly increases their breathability. These fabrics are still waterproof and breathable, but without being 100% windproof—which is a very big deal. Why?
Because air permeable fabrics challenge the main pillar on which the entire outerwear world is currently built, the “Waterproof Above All Else” pillar.
Oh, and not only do air permeable fabrics challenge the pillars that waterproof / breathable fabrics are built on, their existence is threatening to tip the balance of power in the outerwear world. Why?
Because Gore-Tex, the undisputed king in the WPB world, has yet to market a fabric as being air permeable.
This is because the idea of air permeability is in direct conflict with the main pillar of Gore’s philosophy: the “Waterproof Above All Else” pillar.
Consumers have been conditioned for years to think in this “waterproof above all else” mindset, in large part, because of the marketing of the reigning king of the WPB world. Gore-Tex has become such a household name that it has achieved the hallowed commercial status of a proprietary eponym, like Kleenex or Velcro.
Many people believe that they need Gore-Tex to stay dry—that only Gore-Tex can keep them dry—and that is not an easy belief to market against.
But companies like Polartec and eVent are embracing these new air permeable fabrics and attempting to market them for what they really are—a legitimate WPB contender that is not 100% windproof.
For many consumers, “waterproof” and “windproof” are part of a hierarchical system: Waterproof > Windproof > Wind-resistant. And the common assumption is that if a fabric is waterproof, then it is also windproof (and certainly wind-resistant).
But air permeable fabrics disrupt this hierarchy. These new fabrics are waterproof but they are not technically windproof, even though they are effectively windproof.
There is no current label for “Effectively-Windproof” in the standard consumer system of thought.
It will be interesting to see how the public perception of Gore-Tex and the “waterproof above all else” pillar change in the next few years. Although marketing a waterproof fabric that is also air permeable is no easy task, air permeable fabrics are a serious market share contender in the high-end waterproof / breathable realm.
But the real aim of this article is to provide an overview air permeable technology. It is in no way a comprehensive audit of the technology, but I have tried to touch on each of its important features. Air permeable fabrics are relatively new, and where the technology is today may vary vastly from where it ends up in the next few years. It will definitely be fun to watch where it goes. And who knows, maybe we’ll even see an uptick in chair lift conversations that start off, “Sick jacket! What’s the air pressure drop across the membrane?”
Dry Is Dry: The Air Permeable Advantage
Air permeable fabrics (“air perms”) are a complete paradigm shift in the waterproof / breathable (WPB) world.
In the recent past, Gore’s 100% waterproof guarantee was a great reflection of the state of the industry: consumers were first and foremost concerned with staying dry. But the world is changing, and consumers are starting to realize, to borrow some of Polartec’s marketing verbiage, that Dry is Dry; there is no such thing as being more dry. There is very little advantage in a 20,000mm waterproof membrane compared to a 10,000mm rated membrane, which is what many air perms claim to be.
• a 10,000mm hydrostatic water column rating equates to about 14psi
• the hardest wind-driven rain only exerts about 2psi
• you don’t need a 20,000mm membrane to stay dry.
Yes, outerwear is subjected to higher pressures than wind driven rain in the field (falling in wet snow, straps and hip belts on heavy packs, etc.) but these are still unlikely to exceed 14psi.
So air perms are waterproof. They’ll keep you dry. Their advantage is that they purport to offer enhanced breathability.
Breathability: WPB vs. Air Perms
Traditional WPBs are breathable in that they transmit water vapor through the membrane via a single mechanism: solid-state diffusion. (More details on this below, but for a more thorough explanation, I’d recommend hopping over to the Outerwear 101 article.)
Air perms, on the other hand, breathe via two mechanisms: solid-state diffusion and, to a much larger extent (and as the name implies) by moving air directly through the membrane. This is a convective mechanism.
And that is the primary reason for the “enhanced” breathability of air perms: in addition to the diffusive mechanism, air perms also have a convective mechanism that contributes to their breathability.
The second reason, as we’ll see below, is that there are fewer barriers to inhibit the existing diffusion mechanism in an air perm membrane than in a traditional WPB membrane.