About Thermal Underwear

Written by naomi judd
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About Thermal Underwear

Thermal underwear is clothing that keeps an outdoor enthusiast comfortable and safe. This protective clothing helps to insulate the body by creating a small space of air next to the skin. Thermal underwear creates a double space and therefore extra warmth. Read on for the many benefits, functions and types of thermal underwear that contribute to safer and more comfortable winter activities.


People have been layering their clothes for as long as clothing has been around. Of course the first cultures used all natural fibres, such as wool which are still used today due to their excellent ability to hold warmth. Unfortunately, most natural fibres absorb moisture more than synthetic ones. Cotton completely loses its insulating capabilities when wet. In the 1940s and 1950s, hydrophobic fabrics or those that don't absorb moisture such as polypropylene and polyester were invented. Several brands of synthetic underwear were developed in the 1990s and 2000s for specific outdoor pursuits. Some of these include Capilene, Bergalene and Teckwick.


In cold temperatures, the body may battle against wind, snow, sleet or rain and sometimes altitude. The next-to-skin layer or thermal underwear layer should include a top and bottom component. The main purpose of this layer is to wick away moisture from skin and allow warm air from your insulating-mid layers to reach your body. Thermal underwear can mean the difference between hypothermia and a satisfying trip.


There are natural and synthetic thermal underwear fabrics. Wool, cotton and silk are natural layers and polypropylene, polyester, and nylon are synthetics. There are different blends and thicknesses of thermal underwear depending on the brand and what season it is made for. For example a thick layer or wicking polypro dries quicker in the sun after use and absorbs more heat whereas a lighter coloured and thinner weave of fabric can be worn as breathable sun and insect protection on a hot day. They are made from lightweight to expedition weight. Lightweight nylon with some percentage of spandex is often worn by climbers for a bit of added warmth while maintaining full range of motion during a climb.


Staying dry is a number one concern for mountaineers or winter back country travellers. If using thermal underwear, consider getting some that also wicks moisture away from the body as you will still get cold if wet. Never wear cotton base layers if taking part in any outdoor activity. Cotton thermal underwear is not good for much other than an extra layer while cozying next to the fireplace at home.


Wearing a layer under the insulated mid-layers and top weatherproof layers completes a system which enables people to go out into the winter wilds and do the things they love. Thermal underwear helps guard against the four ways humans lose heat: conduction, convection, radiation and evaporation. People that ski, snowshoe, winter backpack, ice climb or mountaineer would not go as far, climb as high or stay as mobile without the essential thermal underwear.

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