Let's start with the technology in the "shell," your outer layer that separates you from the elements. Columbia calls it Omni-Tech. At Mountain Hardwear it's Conduit Technology; Patagonia has the H2No Membrane; then there's Dry Q, Hyvent, Re-Text, Helly Tech. You get the idea. While each retailer has a different name for it, it's the same basic technology invented by the guys who did it first: Gore-Tex.A well-made shell has a three-layer system within it. A system also found in good gloves. The outer-layer is a weather resistant nylon fabric. The inner-layer is usually a soft mesh or synthetic lining. Between the two is what outfitters call the "membrane" layer. This is the part that does the work. It keeps moisture from the elements out, while allowing excess perspiration and water vapor you create to escape. That's critical because when sweat gets cold, the body loses heat more rapidly. Or, worst-case scenario, the sweat can freeze.
So how does that mystery layer keep snow and rain out, but let the sweat vapor escape? In the end, it comes down the size of the hole. Take Gore-Tex, for example. According to the manufacturer, the microscopic pores in their membrane layer are 20,000 times smaller than a drop of water, so rain and snow stay out. Water vapor molecules, from perspiration, are able to escape because these same microscopic pores are 700 times bigger than water vapor from the body. This allows your jacket to breath the extra moisture you build up inside the jacket while keeping the elements out.
Now that we've cracked the science of the outer shell, let's cover another essential part of your winter wardrobe: the base layer. There's a reason you see people walking the streets wearing down vests and jackets and it's not nostalgia for Michael J. Fox's Back to the Future look. It's because it's one of the warmest clothing options. In fact, it's an essential layer in any Mt. Everest climber's wardrobe. Think of down and synthetic down jackets as if you're wearing a sleeping bag. It works by trapping air that's warmed by your body and keeping it close to you. There are important differences between down and synthetic down to consider. When wet, natural down stops working. It clumps up and loses its insulating quality. Synthetic down, on the other hand, while not as warm, maintains some of its "puff" when wet and is generally more breathable. Be cautious though; down has been known to capture too much heat resulting in excess sweat production. Keep that in mind as you plan your outdoor activities. Fleece, another common base layer, is more breathable than both synthetic and natural down while still providing warmth. Unlike cotton, fleece doesn't absorb much moisture and it dries quickly.
One potential innovation in the science of outdoor apparel comes from Columbia Sportswear's Omni-Tech line. You've probably seen the commercials with the ice skiing bikini models. They're promoting what Columbia calls reflective technology. Think of it like the foil blankets that marathon runners get after a race. Columbia's jackets use the same principal to reflect your body heat through little reflective aluminum circles in their jackets. The space between the circles allows the jackets to keep its breathability while reflecting body heat to keep you warm. It's not a completely new idea. The same principal has been used in space suits for decades. Whether the reflective technology is more of a gimmick or not is up for debate. Columbia has also recently added a line of battery-powered electric warming devices to their boots, gloves and jackets.
No matter your brand preference, there is one thing to keep in mind: don't wear cotton. Cotton negates any insulation your gear - expensive or not - may provide. Mountaineers commonly refer to cotton as, "the death cloth," because it absorbs moisture. That's great for bathroom towels, but bad for winter apparel. The danger with cotton is that when you sweat, that moisture sticks to you and when that moisture gets cold your body loses heat. If you find yourself in a bad situation where sweat has been absorbed by cotton, your shirt or socks can freeze. Synthetic materials and wool allow moisture to escape.
When in doubt, remember, Mom was right: layer up. Now, go play in the snow.