Base Layer
Your base layer should be a wicking material like polypropylene, polyester or wool, and it should fit fairly snugly to your body. This is the layer that will take your sweat directly from your skin, keeping you dry and warm while outside. Fabrics like cotton hold moisture, and when air hits a wet shirt it can drop your core temperature quickly. You should be able to get a decent base layer for $25 to $85, as of December 2009, and wool is typically more expensive than poly-blend.
Mid Layer
Your mid layer should offer some insulation, so you can strip down to it when exerting yourself during the climb. Still somewhat fitted, it should have room to move but shouldn't be bulky, as it will need to fit underneath two more layers. Fleece jackets and pullovers are efficient here, but the traditional wool sweater also works well. You can get a great basic fleece jacket for about $70 to $150, as of December 2009.
Insulation
An insulating layer is important for winter mountaineering because it will keep you toasty during periods of lower exertion like ski descents or belaying. There are two choices here, down or synthetic fill. Down is puffy and warm, but loses its insulative capacity when wet, so it's not a good choice for rainy conditions. Synthetic fill layers make for a slimmer fit that's not as warm as down, but still functions well when wet. Quality insulation layers are pricey, ranging from $150 to $300, as of December 2009.
Shell
A shell layer should be wind-resistant and waterproof for winter mountaineering. Because you'll be on snow for 99 percent of your climb, having a barrier is essential. This is the layer where you'll want to focus on bells and whistles for your comfort: a hood that fits over your helmet, pockets that are accessible around your pack straps and pit-zips for easy ventilation on the ascent. Because of the need for quality construction, a good shell layer will probably cost you between $200 and $400, as of December 2009.
