Layering
Layering (wearing multiple layers of different fabrics) is the most effective means to properly thermoregulate without excessive overheating. In other words, as temperature conditions and/or activity levels change throughout the day, you can add or remove layers of clothing as necessary to maintain a comfortable body temperature. Two important things to keep in mind when layering: 1) the layers should not restrict your movement in any way, and 2) when purchasing an outer layer remember that you'll need some extra space so you can comfortably fit the inner layers underneath without your garments fitting too tightly (if the outer layer is squeezing the inner layer(s), you're effectively compressing the dead air space within the inner layers, thereby reducing their insulation value and your warmth). This is not a system that you can perfect overnight; it's going to take some experimentation to determine which combination of fabrics work best for you and which specific layers you'll require in various situations. Examine the following factors to thermoregulate properly, but know that you can modify one or all to suit your specific needs during various situations and activities:
- Clothing Layers The number and type of layers you wear allows you to create sufficient dead air space for insulation and protection from external conditions such as wind and rain. During the cooler hours of the morning or the evening, or when your activity level drops, such as during a hiking break, extra layers may be added as necessary.
- Activity Level Increasing or decreasing your level of activity increases or decreases the amount of heat you generate.
- Staying Dry Because you can lose heat 25 times faster in wet clothing than in dry clothing, minimizing wetness is an important factor in retaining heat. Moisture comes externally from rain or snow or internally from perspiration generated by exercise. Your layers of clothing should minimize the buildup of moisture close to your skin but also protect you from external moisture.
- Ventilation Some garments allow you to open (unzip) or close up (zip up) your clothing to ventilate, or increase or decrease heat loss, without having to actually remove or add a layer. Ventilation also prevents moisture buildup from perspiration.
At its most basic level, each layer has its own function. The base layer is your next-to-skin layer and is responsible for managing moisture. The insulating layer goes over your base layer and is responsible for retaining warmth. The shell layer goes on top and protects you from the wind and rain. You can add or remove layers as necessary to maintain a comfortable temperature.