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just when you thought it was safe to go get that pricy eVent storm shell, quasi-softshells made from polartec neoshell are going to hit the shelves this fall. will this new fabric the new standard by which all other waterproof/breathable fabrics will be judged? polartec's marketing says it breathes 'twice as well' as the next best fabric yet remains fully waterproof - and has some stretch and give like a softshell.
i suspect it will be hard to tell. so far as i am aware, there are no universal testing standards for measuring how waterproof or breathable a fabric really is.
water resistance is generally derived from the amount of water pressure a fabric can withstand (in millimeters) before leaking. i think this is interesting, but should water pressure really be the measuring stick? stretching a sheet of gore tex or eVent and spraying it with a garden hose doesn't have much in common with the field conditions most people encounter. to provide some real-world perspective, rain driven by hurricane-force winds exerts roughly 10 PSI of force. that's 6680mm, well less than the waterproofness ratings commonly associated with gore tex or eVent, or the 10,000mm i have seen thrown around for neoshell. we are much more likely to see a day alternate between drizzle, stead rain, and bands of thunderstormsand to have fabric that is sat on and scrunched under a hip belt and shoulder straps. how much psi does a backpack shoulder strap or hipbelt exert? what if you sit on a wet log on a break? i don't think anyone knows or has tested that. (marketing materials will usually cite figures between 10,000 and 30,000 mm),
breathability is generally derived from the number of grams of water that can pass through a membrane in a 24 hour period. (marketing materials will cite figures like 10,000 grams/millimeters squared/day). it looks to me like polartec is trying to say their fabric is more breathable 'in active conditions' because the fabric is mildly more permeable to air. whether that really makes a difference is anyone's guess at this point.
i guarantee, though, that these neoshell jackets will get rave reviews because people will see them as the holy grail, finally, a truly waterproof softshell that retains the breathability.
REI published a nice, detailed article about this: http://www.rei.com/expertadvice/articles/rainwear+how+it+works.html
a report of the military's test results (if you can understand it) is also out there: http://www.shelby.fi/tips/breathability.pdf
should be interesting. if anyone has any thoughts about the neoshell, happy to hear about it. my view is that an open vent to the outside, whether it's a pit zip or simply unzipping the front of your jacket, is a quick, easy, and effective way to vent moisture, but it doesn't hurt to have a jacket that breathes.