Waterproof gear and "wetting out"

So, in my search for a rain jacket, I was considering a few that were super lightweight and supposed to be very breathable. Then I came across a blog that talked about something I knew on one level, but hadn't actually taken to the logical conclusion.

Every rain jacket with a waterproof membrane (Gore-tex, eVent, etc.) has at least 2 layers of fabric to it: the actual waterproof membrane, and the outer layer that is visible to the world. That outer layer is there to help with durability/abrasion resistance. The outer layer also helps with waterproofing by having a chemical waterproofing agent on it. That chemical does fade over time, though. Hence the reason REI sells waterproofing washes and sprays.

Breathability is how much air (especially water vapor) can escape through a material. The more breathable a jacket, the less you sweat while wearing it. The less breathable, the more you are going to sweat, even in cold weather. Usually, the waterproof membrane is the least breathable part of a jacket. This is why most membrane manufacturers are in a race to make more breathable, but still fully waterproof, materials, and it is a huge advertising point.

The process of "wetting out" pretty much negates all benefits of breathability. Wetting out is what happens when the outer layer of a jacket gets soaked. It becomes so full of water that there is no longer any breathability because the water forms an air-proof barrier. The waterproof membrane might still be protecting your skin from the rain, but the lack of breathability means you are going to get wet from sweat. This is why most jackets have some sort of venting, be it a flap on the back or pit zips.

The jacket that first caught my eye was the Outdoor Research Helium II jacket (http://www.outdoorresearch.com/en/mens-helium-ii-jacket.html). Super lightweight, very packable, and supposed to be highly breathable. The lack of pit zips, though, turned me off.

The next jacket was the Marmot Essence (http://marmot.com/products/details/essence-jacket-new). Just as lightweight, this one uses pit vents instead of zips to save the weight of the zippers (every ounce counts on long hikes). Also very packable and breathable even without the vents.

Looking at Marmot brought me to the Super Mica (http://marmot.com/products/details/super-mica-jacket-new). It only weighs a bit more than either of the other two, uses the same waterproof membrane as the Essence, has pit zips, 2 pockets (the other two only have one), AND has reinforced areas where a backpack will be resting. I picked it up and have needed it on one hike so far. The breathability is no joke. I think I'm going to be very happy with it on the trail.