Windshirts are complicated, because their job is a difficult one, and an important one. Patagonia’s Airshed, a pullover shirt made from the outer fabric of the Nano Air series, has been around for a few years.  The lack of a hood, concerns over durability, and the expense put me off for a while, but Max’s glowing review, a gift card, and a 50% off sale put me over the edge last winter.  That I’ve put off writing this for close to a year, and still struggle to summarize performance, is evidence of what an odd duck the Airshed is, as well as how action layer performance doesn’t emanate directly from lab numbers.

The relevant numbers are that the Airshed fabric is 44 grams/meter, and the claimed air permeability is 67 cfm (cubic feet/minute).   The Patagonia Houdini, touchstone for the traditional modern windshirt, is 40 grams/meter and somewhere around 5-10 cfm (being over the head of the general public, cfm is not generally featured on product pages).  The BD Alpine Start, touchstone for modern soft shell windshirts, is 80 grams/meter, and roughly 30 cfm.  In theory, the Airshed ought to be breathable like an Alpine Start class windshirt, but as light and thus as quick drying as a Houdini class windshirt.

In this, it succeeds, though as the significantly increased cfm would suggest, the Airshed does not provide the same warmth as the Alpine Start.  This has a lot to do with breathability, but also I think a lot to do with fabric weight and drape.  The Airshed fabric is impressively pliant, and offers exceptionally little resistance to breeze killing dead air space.

At the same time, I found the Airshed oddly not breathable.  During sub zero conditions it accumulates less moisture on the inside surface than the Alpine Start, but during warmer conditions (say 60F) felt stuffy faster.  I’ve worn the Alpine Start as a sun layer in a packraft on a few occasions when I only had a short sleeved baselayer.  Oddly, I’d be less comfortable using the Airshed for the same purpose.  Somehow the Airshed seems more responsive when the moisture gradient between the inside and outside of the fabric is greater.  I also found it unpalatable to wear against the skin.  It dries fast, faster than modern light (~100 grams/meter) baselayers, but does not actively wick, and thus feels clammy.  It feels very similar to the old BPL Thorofare; uberlight, bugproof, quite windproof, and somewhat plastic-baggy.

For these reasons, I haven’t worn the Airshed a whole lot.  I’m also not a fan of several key features.  The chest pocket zipper is weighty relative to the gossamer fabric, and doesn’t run well unless the neck is zipped almost all the way up.  I removed the pocket, something of an ordeal as the light fabric puckers and pulls like crazy.

The second, and far more significant issue, is the stretch fabric along the cuffs and hem.  This stuff holds water like crazy, an attribute highlighted by how fast the main fabric dries.  Not really a huge deal for a trail running shirt, but an almost fatal flaw in a backcountry piece.  After the struggle of canceling the pocket, I’ve yet to tackle replacing the hem fabric.

Durability has been passable.  There is significant pilling around the front of the waist and along the sides, where the hipbelt action is, but I haven’t yet put a hole in it from brush, which somewhat exceeds expectations.

After a summer of disuse, or of bringing the Airshed and wishing I’d brought the Alpine Start, I cut the sleeves off (easy, the seams are right there), and as a vest the Airshed has promise.  My perhaps longest running complaint about wind or action layers is that they have to be removed and stowed away during serious rain.  Light ones like the Houdini mess significantly with the breathability of a WPB layer, while more breathable ones like the Alpine Start hold too much water, while not contributing enough to the insulation scheme.  My new Airshed vest promises to be a wind layer that can stay on, over a baselayer, for days at a time of mixed weather.

Time (and spring) will tell.