Editor’s Note: Remember that clothing is the first layer of shelter you have available. If you can address three or four of these points, you’ll be much better suited for cold weather survival.
The ways that heat from your body can be transferred to the environment are called heat loss mechanisms. In a hot climate some of these mechanisms can be used to your advantage, but in a cold weather survival scenario they can all be detrimental.
#1 Heat Loss Mechanism: Radiation
Radiation is the primary cause of heat loss. Our body radiates heat to the environment much like the sun radiates heat to the earth or a campfire radiates heat to keep us warm.
At 50 degrees F, 50 percent of the body’s heat can be transferred to the environment through an exposed head and neck. We can also lose heat from our wrists, hands and feet.
#2 Heat Loss Mechanism: Conduction
Conduction is the process by which we lose heat through direct contact between objects. This can occur when sitting on a cold or snow-covered stump or rock, when wet clothes come in contact with your body, by touching cold objects with bare hands, or by kneeling on the snow to build an emergency shelter. Avoid these situations to prevent conduction of heat from the body to other objects.
#3 Heat Loss Mechanism: Convection
Convection is loss of body heat due to movement of air or liquid across your skin. An example of convection is wind chill. Through radiation, the human body is always warming a thin layer of air next to the skin. The temperature of that layer of air is usually equal to that of the skin. When this layer of warm air is undisturbed, the body stays warm. However, if this warm layer is removed by convection, the body quickly cools down.
#4 Heat Loss Mechanism: Evaporation
Evaporation is a process whereby liquid changes to vapor, during which heat from the liquid escapes to the environment. In a cold environment, it is essential to wear fabrics that breathe. If water vapor from perspiration cannot evaporate through clothing, it will condense, freeze and reduce the insulation value of the clothing. This will cause your body temperature to go down.
#5 Heat Loss Mechanism: Respiration
We lose heat through our normal breathing process. You can observe this when you see a
person’s breath on a cold day. This is heat from the body lost to the environment. It is also difficult to prevent this loss, as we have to breathe.