To enjoy the winter, especially when going outdoors, it means just one thing - keeping warm and dry. That is why layers of material are always suggested, because air is trapped between each layer. This air must be dry, however. Air insulates, keeping in body heat, but moisture conducts that heat away. Everyone is aware of moisture that comes from the outside - rain and snow - but many don't know that inner moisture coming from the body can cause as much trouble in keeping warm as the more obvious outer dampness.
The common outdoor fabrics (wool, down and the synthetics such as pile, polyester, dacron and polypropylene) all provide adequate insulation.- Down - Down provides superior insulation at the lightest weight. It loses its insulating value when wet and is impossible to dry in the field.
- Synthetics - Synthetics provide insulation, retain good insulation value when wet and dry relatively quickly. Individual fabrics vary in insulation, weight, compressibility, durability, cost, fabric uses and drying and wicking ability. The synthetics include polypropylene, capiline, the polyester insulators such as quallofil, thermoloft, holofill, dacron, polargard, kodofil, thermalon, thinsulate, thermore and the piles such as borglite, polarplus and chinella.
- Wool - Wool is heavier than the synthetics, durable, insulates well and retains insulation ability when wet. All but the heaviest wools will dry in the field.
- Cotton - Cotton is a less efficient insulator than wool, the synthetics or down. When wet it increases its thermal conductance nine times. It absorbs moisture and resists drying. It's great in warm weather but is not suggested for cold outdoor weather. Outdoor experts have called it the "death cloth' if used in cold outdoor weather.
Outer fabrics and shells
When guarding against the elements, the outer clothing barrier should be a breathable, waterproof or breathable/waterproof shell garment. All three reduce heat loss from convection (windchill) and provide some degree of protection from rain and snow.
- Breathable fabrics shed snow, resist rain and allow body moisture to pass through.
- Waterproof fabrics can protect you from outside moisture. During exercise, insulation can become wet from accumulated moisture inside the garment. It's not usually worn in the winter due to the condensation problem.
- Waterproof/breathable fabrics are membranes with pores small enough to block passage to large water droplets while allowing the smaller water vapor particles to pass through. They have proven effective in winter, less so in warm, wet weather. Their high cost can be a drawback.
Winter layering
Layering provides the best insulation by allowing adjustment of the amount of insulation to fit the activity and environmental conditions. Insulation can be added as you cool down or removed to prevent overheating and sweating. Layers should be larger and looser fitting to trap warm air, allow freedom of movement and allow circulation to the extremities.
Underwear layer
Winter underwear can include a layer of light to medium thickness polypropylene or woolen long-john bottom and top; the basic insulation layer is only removed in warm weather. Shirts with buttons or zip turtlenecks provide more ventilation options.
Polypropylene is a common choice as an inner layer that transfers moisture from the skin to the outer layers. Polypro absorbs less than 1 percent of its weight in moisture.
Insulation layers
These are one or two layers added as insulation as needed. A variety of fabrics and garments are possible: wool, pile, down, synthetic insulation in sweaters, jackets and coats. Be sure to fit the layers over each other without constriction or restricting movement.
For a winter trip into Yellowstone or other such winter outing, a usual combination is one polypro layer plus two other insulation layers (wool or pile jackets or sweaters) for the upper body and one polypro plus one additional layer for the legs. An additional outside insulation layer is used if camping outdoors.
Outside insulation layers are insulated parkas, insulated pants or snowmobile suits that provide insulation when inactive, on snow machines or in extreme conditions.
Shell layers
A shell is worn to cut the wind and keep dry in the snow. Breathable wind clothing blocks wind but is not waterproof. Waterproof gear causes insulation layers to become wet from our own body moisture during activity. Wear waterproof gear only in the rain. Waterproof/breathable fabrics such as Goretex, Klimate and Ultrex are nice alternatives to waterproof gear for outdoor winter conditions.
Head protection
Keeping the head warm is important. Scarfs or neck gaitors are popular as light and effective insulators for the neck. Hats of wool or synthetics should cover the ears.
Hand protection
Mittens insulate better than gloves. Gloves provide better dexterity. Mittens with a silk or polypro glove liner are a good combination when occasional dexterity is needed. Waterproof/ breathable or waterproof palm mitten shells keep wool mittens dry.
Foot protection
Two pairs of wool socks are commonly used as insulation. Polypro liners work well as smooth inner socks, especially inside a vapor barrier liner. Some people use a vapor barrier liner over a polypro or wool sock. This decreases heat loss and keeps outer socks and boots drier. If your feet sweat, vapor barriers may be a good idea. Plastic bags or waterproof nylon are used, as are neoprene socks.
Anything tight on the feet or lower legs causes cold toes. Be careful of tight gaitors and boots. An extra pair of socks causing a tight boot fit often produces colder feet than the wearing of fewer socks. Fit your boots with insoles. They make a big difference in conductance through the bottom of a boot.
Conditions in the Mountain West often expose people to cold winters. People die because of improper planning and preparation, which often includes inadequate clothing.