Nov 22, 2010
Author: Gerhard Gross
It’s minus 20ºC. Each chairlift ride you’re huddling deep into your hood, cupping your mitt around your face to keep your nose from going numb. And there below, as happy as a hipster at a rave in a Japanese raw salvedge denim warehouse, is some dude riding in jeans. So why, without the expensive outwear, is DJ Denim loving life?
The reason, according to REI Gear and Apparel research and development engineer, Steve Nagode, is that jeans breathe really well. Which means they’re good at letting moisture from your body evaporate, even if they’re not good at keeping water out. In cold, dry weather snow won’t make you wet unless it gets in your clothes and melts. But even the best outerwear won’t keep you dry if your own moisture can’t escape.
“When it’s really cold, and you’re not going to get wet from snow, you’re better off to have all the vents [on your waterproof breathable outerwear] open to keep the air moving through,” says Nagode. “You don’t want to collect the warm, moist air because as it moves towards the inner surface of your shell it will turn into condensation, just like a steamy window.”
In wet conditions, where you want to keep your vents closed, the breathability of a garment really comes into play. Breathability is the amount of water vapor, in grams, that can pass through a fabric in a 24-hour period. It’s given in varying amounts, such as 5000gm, 10,000gm, or 20,000gm, depending on the performance of the garment, and is usually combined with waterproofing rating written as 5000mm/5000gm. Waterproofing is calculated as the amount of water pressure, in millimeters, a fabric can withstand before leakage occurs. A higher breathability usually means a higher retail price, but it also means more warm, moist air can escape. And that, Nagode says, is almost always better if you want to stay dry.
Electron microscope top view of a waterproof breathable membrane.
For homeboy in the jeans, wet conditions mean he’s going to be uncomfortable—but only if he gets cold. Skin can perceive just three sensations: temperature, pressure, and pain. It doesn’t have sensors for wetness.
“Take your jacket, wrap it around your hand, and stick it in a cold sink full of water,” says Nagode. “Your hand will feel wet. But it’s not wet, it’s cold.”
The same thing happens when you sit on a chairlift and your ass feels wet in waterproof outerwear, when it’s often just cold. When a garment is dry it takes on a temperature closer to your body temperature and it’s easier to stay warm. That’s why a good durable water repellant (DWR), the stuff that makes water bead off your outerwear, is important.
“If you’re well below zero and everything falls off your jacket anyway,” says Nagode. “If you’re getting water on it, it’s not beading up, and it’s wetting on the surface, that makes the whole jacket cold and you end up getting lots more condensation on the inside.”
Having properly sealed seams and zippers also play a role. Even with the best fabric, you’re going to get wet if seams aren’t taped. As a test, Nagode suggests wetting a jacket and crumpling it into a little ball. If the seams aren’t properly sealed, he says, the water will drip right through.
Interestingly, Nagode feels that the high waterproof ratings of garments are, well, overrated. Waterproofing typically ranges from 2,000mm on the low end to 20,000 and above on the high end.
“20,000mm is the pressure exerted by a column of water 20 metres high,” he says. “Precipitation just does not come down at these pressures. For example, a tent fly is rated to a maximum of 2,000mm and is 100 per cent rainproof. If we raised the rating to 4000mm, the occupants would still not get wet, because 4000mm is just as rainproof as 2000mm, not more rainproof, not 200 per cent more rainproof, simply rainproof. Jackets do need a bit more waterproofing than a tent due to wind-driven precipitation, but 5,000mm should cover all situations.”
The basics of waterproof breathability.
Nagode’s statement runs contrary to the idea that a high waterproof rating means you’ll stay dry, and not everyone agrees with him. Carl Moriarty is a designer for Arcteryx, a brand that makes outerwear with a minimum rating of 28,000mm/17,000gm. Arcteryx believes that waterproofing, and the comfort the technology provides, comes from the combination of the face fabric and the ability of that fabric to shed water while resisting contaminates.
“The place where we would differ from REI is that in snow sports you tend to sit down in wet conditions,” says Moriarty. “By sitting you can easily overwhelm 5000mm coating. The second thing to that is that all polyurethane coatings tend to loose their waterproof integrity, with flexing, washing, and abrasion, if you start at 5000mm you quickly deteriorate to half that within a year of use. We would argue that [waterproofing] is infinitely more complicated than just a simple number.”
To make things more confusing, there’s no standardization for waterproof breathability tests. It has been well documented (http://www.rei.com/expertadvice/articles/rainwear+how+it+works.html) that different brands use different methods of testing. There is some danger that they can choose the test that will produce the most favourable results for their product, producing a rating that may not be entirely accurate.
So where does this leave you when you’re looking for new gear?
“Buy for the conditions you expect to find yourself in”, suggests Nagode. “If you’re looking for a waterproof breathable shell, and water can be a factor, then seam taping matters. If you’re in a place where it’s cold enough, where water doesn’t really matter, then you don’t need the taped seams because what you’re looking for is windproofness. If it’s really cold, the powder skirt might be a feature that you look for more than taped seams because you don’t want the snow to fly up in the jacket.”
The most expensive gear doesn’t necessarily mean it will be the best for where you plan to ride. So ask your retailer questions, and look for features that will best suit your environment. Who knows, if the conditions are right, maybe all you need to do is grab that old pair of jeans from the closet.
For more on how waterproofing and breathability work go to: www.rei.com/expertadvice/articles/rainwear+how+it+works.html
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