By The Numbers- How Much Wind Penetrates Your Air Permeable Outer Layer at Hiking and Running Speeds

Hi Meta:  My winter uniform is Brynje, HH Lifa or Finetrack, Alpha 60, and a wind layer, which is usually a Shakedry jacket with 20″ pit zips.  I wear this for hiking, backpacking, and backcountry skiing.  Of course, you will need to vary the layers according to your level of exertion and wind/temperature conditions.  If it is particularly cold, I might replace the Alpha 60 with an Alpha Duo, which is two layers of Alpha 60 sewn together by Farpointeog.com. I also sometimes layer an inside-out Mountain Hardwear Airmesh over the 60 gsm Alpha Direct. When this is used without a wind layer, vapor can freeze at the ends of the exposed napped fibers of the Airmesh and then simply be brushed off. This works nicely when the cold winds are not blowing too hard.  When it gets really cold, such as high winds and temps in single digits F or below, I might cover the whole ensemble with a puffy such as a Patagonia Micro Puff or, with even lower temperatures, a Patagonia Macro Puff.  I don’t carry two Puffs; I decide which to carry based on the conditions I expect.

I do not use Merino layers. I think it would generally reduce the MVTR of the ensemble and trap more moisture in its fibers due to both its hydrophilic properties and typically denser knit than the garments I described above.