If you’re too cold, too hot or too wet, its hard to think happy thoughts, let alone enjoy what you are doing. Dressing in layers, instead of one bulky "do everything" garment, can help prevent uncomfortable and potentially dangerous situations, such as hypothermia. Layering is the relatively simple concept of dressing in a way that allows you to adjust to a wide range of environmental conditions.

To provide an optimum working environment, your internal systems try to maintain a thin layer of warm (30° to 33°C.), still air around your body. If the surrounding environment were constant and your life was void of activity, this private micro-climate would be all you would need. But once you step outdoors, you run the risk of knocking your micro-climate out of whack because of physical activity, wind temperature and moisture which can all create conditions too extreme for the body’s mechanisms to adapt to. Wearing several thin layers will allow you to maintain an optimum micro-climate during periods of physical exertion, as well as during times of inactivity. By dressing this way, you can fine tune your micro-climate by shedding layers before you get too hot or by adding layers before you start cooling down.

INNER-LAYER

Referred to by most people as underwear, this layer plays the most critical function of the system. It must transport moisture, usually in the form of sweat, away from the skin and disperse it to the next layer where it can evaporate. Why? Water is a very good heat conductor. A wet garment against your skin can draw heat away from your body twenty-five times faster than a dry one. Even in conditions above freezing, this rapid heat loss can cause a dangerous drop in your body’s core temperature, leading to hypothermia. Synthetics such as polypropylene and polyester now dominate as the materials of choice for this layer. Synthetics are light, strong and best of all unlike natural fibers synthetics absorb very little water. This quality makes for quick-dry materials, reducing the risk of conductive heat loss. Synthetic underwear is available in light, medium and heavy weights to meet the demands of different activities. Light-weight for sustained activity where moisture transport is paramount. For changing activity levels, mid-weight allows a balance of wicking and insulation value. Heavy-weight is for those times when your activity level is limited to watching the temperature drop. The inner-layer should fit snugly but not be so tight as to feel restricting.

MID-LAYER

The mid-layer provides insulation and continues the transportation of moisture from the inner-layer. To slow heat loss, this layer must be capable of retaining the warmth that is generated by your body. Wool and synthetics are well suited for this purpose because the structure of the fibers create small air spaces that trap molecules of warm air. As far as moisture management goes, synthetics have the upper hand because they absorb little water, allowing faster evaporation. Wool absorbs up to thirty percent of its own weight in water, leaving it heavy and difficult to dry. Synthetic fleece/pile garments (pants, jackets, pullovers and vests), as well as being lightweight, are very durable and require less care than wool. Additional features such as pit zippers and full length front zippers allow venting. As with the inner-layer, this layer should be snug but not constricting. If it’s too loose, it just means more space your body has to warm up.

OUTER-LAYER

The outer-layer protects your micro-climate from the elements. It should also allow air to circulate and excess moisture to escape. Choose on the basis of what you plan to do, where you plan to do it and what you plan to spend. For dry conditions, a breathable (uncoated) wind shell may be all you need. If you expect conditions to be more severe, a waterproof (coated) rain jacket with additional insulation may be more in line with your needs. A shell made of a breathable/waterproof fabric, such as Gore-Tex®, will give you protection from wind and rain, as well as allowing water vapour to escape. However, there are no miracle fabrics. When you are active, your body can produce more water vapour than any fabric can pass. The result can be a build-up of moisture on the inside, leaving you wet, clammy and cold. Strip off a layer or open any ventilation zippers before this happens and you’ll be a happier camper.

HEAD PROTECTION

It has been estimated that up to fifty percent of a person’s total heat loss can occur through the head. This is because your body considers the head to be a rather important extremity and therefore pumps a hefty volume of blood to it, keeping it warm and functional. Subsequently, your head acts like a radiator, letting heat escape. This puts a strain on the rest of your system because your body must now use additional energy to rewarm the blood as it recirculates. A good wool or fleece hat will not only slow heat loss through your head, it will also make your hands and feet feel warmer because of the improved circulation. Don’t overlook full-face balaclavas and neck gaiters for those really harsh conditions.

HANDS AND FEET

In its effort to keep your head and torso warm in cold conditions, your body reduces blood flow to the hands and feet. As well, these areas do not generate much heat on their own, so some protection is needed. Mittens are warmer than an equivalent pair of gloves because the whole hand contributes to the warming process. The disadvantage is a sacrifice in dexterity. Gloves are good for activities that require independent finger control, such tying knots, but each finger must warm up its own little compartment, making them less efficient at keeping your hands warm. A layering system that consists of a thin wool or synthetic glove for moisture transport, an insulating mitten and a non-insulated shell mitten for outer protection will give you a wide range of temperature control and manual dexterity.

Wool is still the dominant choice for socks, offering a good balance of moisture management, insulation and cushioning. The addition of a polypro liner sock will speed up moisture transport from the feet to the outer wool layer. Socks should fit snugly. Too tight and circulation can be restricted. A loose sock can slip or bunch up, creating pressure spots that can lead to blisters.