Staying warm in the great outdoors is an important bushcraft and survival skill. In cold conditions in the wilderness you can lose heat through a number of different processes – radiation, convection, conduction, evaporation and respiration (breathing).

Radiation: Whenever you sit by a good fire and feel its warmth, you are benefitting from heat radiated by the fire. Another way to look at this is that while you are gaining warmth, the fire is losing heat to its environment. It’s the same for you when everything around you is cold: You may radiate warmth and so be losing body warmth to your surroundings.

Many folks think that heat loss from radiation occurs just from exposed skin. But even if you’re dressed, heat radiates from your body to your attire, then from your attire to your local environment.

Convection: Convective heat loss happens between a material surface and a moving fluid or gas in contact with it. The air closest to your skin is heated by the body. If this warm air is permitted to move away from your body, colder air will take its place and more heat will be lost in warming this cold air. Putting on insulating layers of clothing helps to hold warm air near to your body. It is the air kept in your attire that helps to keep you warm,, not the clothes themselves.

Particular attention should be paid to insulating your core body area; the head, neck, trunk and groin. There is certain to be a good blood supply to your head and there is always a lot of warm blood passing near to the surface of your neck. Therefore , it is always sensible to have a warm hat with you, even in summer. It need not be heavy: A merino wool beanie is a great choice. In less warm conditions, you need to also include a head-over or neck-warmer to prevent heat loss from your neck. These things, despite being little, can make a massive difference to how warm you are on a cold day, if the weather conditions turns bad, or if you have got to spend an unplanned night outdoors.

Wind and low temperatures can create the potential for large convective heat loss. Unless your outer clothing layer is windproof, cold air passing over your body will remove the warm air and take heat away from you.

Conduction: Heat loss thru conduction comes as a result of direct contact with cold surfaces or objects.

Aluminum is a very good conductor. Water is a good conductor of heat. Air is a poor conductor of heat. That is the reason why it is so good to have air captive in your clothing to insulate you. It’s good to insulate your body from cold surfaces with a poor conductor. A typical example of this is the utilization of a sleeping mat when camping out. If you sleep in direct contact with the ground, you lose a lot of heat into the earth. If you’re building a shelter, make sure you build a good bed, with acceptable insulation.

Avoid handling cold objects, in particular metal, with your uncovered hands. Do not touch metal objects with your bare hands in temperatures much below 0 degrees Celsius (32 degrees Fahrenheit) as they can cause near-instant freezing of skin. Even when you are using gloves, limit how much you handle metal objects in sub-zero (Celsius) temperatures.

Evaporation: To convert a liquid to a vapor or a gas needs energy. What this implies is when sweat on your skin or moisture in your clothing evaporates, this evaporation draws heat away from your body. This is known as evaporative heat loss.

Evaporation is a very effective mechanism for getting rid of heat. It explains why sweating works so well at keeping you cool. The darker side of evaporation is that if you get wet in a cold environment, it’s possible to get extremely cold, very fast. Therefore, it is critical that you do all that you can to stay dry while in the outdoors.

Your first line of defence agains this sort of heat loss is effective waterproof outer clothing to stop rain, and other water, getting into your clothing. But it is not solely about stopping water getting in; you need to attempt to minimise the quantity of sweat in your clothing. When you exert yourself, getting wet from the inside could be a more serious issue than water coming in from the exterior of your clothing. Breathable fabrics that permit perspiration to escape will provide help to an extent but if you’re working hard, you can still get sweaty and damp.

If you pay attention to the environmental temperature and your level of exertion you can help to maintain an even body temperature and minimise sweat by adjusting layers, especially taking layers off prior to starting exercising. Ventilation also helps – open up front zips, expose the neck, and so on. Adjust your clothing as required during exercise. You may control our activity level; if you’re still getting hot and sweaty in spite of the above measures then you should doubtless slow down a bit and. Pace yourself.

Respiration (breathing) : As you breathe in cold air it is warmed before it gets to your lungs. You then breathe out warm air and you are effectively losing heat each time you breathe. There is nothing we are able to do about breathing. We have to do it to remain alive! Compared with the other mechanisms of heat loss , though, heat loss thru breathing is relatively unimportant.

Conclusion: So these are the five ways you lose heat to the environment in the wilderness: Radiation, convection, conduction, evaporation and respiration. If you understand these heat loss mechanisms well and mix this understanding with your expereience of the outdoors, it should help you stay safe and less likely to suffer from hypothermia.

Paul Kirtley teaches bushcraft and survival skills. He’s committed to nature, wilderness and remote travel. This is something that comes across clearly on his bushcraft courses.