

How do these membranes work? The quick answer is that they prevent exterior moisture from entering while allowing interior moisture to escape. Typically waterproof/breathable membranes have a pore structure that keeps rain out while giving our sweat a path of least resistance to the outside world. Footwear and outerwear that use waterproof/breathable membranes need a special construction process that guarantees the membranes work as intended, known as "seam-sealed" construction, which means anywhere there is a stitched seam, that seam gets "sealed" with a special seam tape which maintains the integrity of the membrane.
Almost everybody is familiar with the name Gore-Tex, as it has become the household name in waterproof fabrics. Started thirty years ago in 1978, Gore created the first product that took us from the waxed cotton and rubber era and ushered us into an era where fabrics started to mimic our own bodies natural evaporative heat-loss process. Gore-Tex is still synonymous with the idea of "waterproof" and as a brand, is instantly recognizable--when we see the Gore-Tex tag on products we know it means that we're going to stay dry. However, there are other choices when it comes to waterproof/breathable fabrics, such as eVent, Keen Dry, 3XDRY by Schoeller, Sympatex, Membrain, and others, all of which are equally adept at keeping moisture out, while doing their best to move moisture from the inside out.
The biggest challenge in waterproof/breathable membranes is the "breathable" part, with the ultimate goal being to wick moisture away from our skin and move it through the fabric to the outside environment, and each company approaches this process differently. Some, as with eVent, use a micro porous membrane with "millions of tiny pores" to achieve this, allowing interior moisture to vent directly to the outside. Schoeller uses what they call 3XDRY, which is a water repellent exterior, a moisture absorbing interior, and a sandwich layer that disperses the collected interior moisture over a large surface area to evaporate it quickly. And Gore-Tex utilizes a pore structure that is smaller than a water droplet, but larger than moisture vapor to wick moisture away from your body and transport it through the membrane to the outside.

In the end, we are a far cry from the waxed cotton and rubber boot days, and we expect our performance fabrics to, well, perform. And they do indeed perform, as long as we are understanding of their current limitations. So, if you're standing in a puddle and you want your feet to stay dry, look to almost any waterproof/breathable footwear to do the job, but then you might want to ask yourself, "why am I standing in a puddle?"
Market Street Athlete