Winter Underwear - The Base Layer (Foundation)
 - Arctic / Antarctic, Cold Weather, Thermal Clothing

The base layer is the layer next to the skin, usually thought of as being underwear, or in cold climates, "thermal" underwear. Despite cold temperatures, perspiration is still a problem, in fact it can be more so than in a temperate climate. The body loses moisture at almost all times whether undergoing any great level of exertion or not. If there are numerous insulating layers keeping you warm, then it is more difficult for the perspiration to be able to escape. If the perspiration is not removed it will result in the wearer becoming uncomfortable and a feeling of "clamminess" as well as decreasing the efficiency of the insulating layers.

Underwear that is able to wick this moisture away from the skin surface therefore becomes much more important and this is an important factor in choosing garments. Modern "thermals" are made of synthetic fibers such and polypropylene or "fleece" that have good insulating properties and are also able to efficiently wick moisture away from the skin. Zips at the neck or even full length can help regulate temperature. A golden rule is to avoid cotton.