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

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

Many people think that heat loss from radiation happens just from exposed skin. But even when you are clothed, heat radiates from your body to your attire, then from your clothes to your surrounding environment.

Convection: Convective heat loss happens between a physical surface and a moving fluid or gas that is moving over it. The air closest your skin is heated by the body. If this warm air is unconstrained so that it is free to move away from your body, colder air will take its place and you will lose more heat 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 garments that helps to keep you warm,, not the garments themselves.

A good amount of care and 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 brain and there is certain to be a lot of warm blood passing close to the surface of your neck. Therefore , it is always good to have a warm hat with you, even in summer. It doesn’t have to be heavyweight: A merino wool beanie is a good choice to have with you. In chillier conditions, you must also include a head-over or neck-warmer to curtail heat loss from your neck. These things, although small, can make a massive difference to how warm you are on a cold day, if the weather turns bad, or if you have got to spend an unplanned night outdoors.

Strong winds and low temperatures can combine to produce great convective heat loss. Unless your shell clothing layer is windproof, cold air passing over your body will displace the warm air and take warmth away from you.

Conduction: Heat loss thru conduction comes thru 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’s so great to have air captive in your clothes to insulate you. It’s good to insulate your body from cold surfaces with a poor conductor. A common example of this is the utilising 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 are building a shelter, make sure you build a good bed, with adequate insulation.

Avoid handling cold objects, particularly metal, with your bare hands. Don’t touch metal objects with your unprotected in temperatures much below 0 degrees Celsius (32 degrees Fahrenheit) as they could cause near-instant freezing of skin. Even if you’re using gloves, limit how much you handle metal objects in sub-zero (Celsius) temperatures.

Evaporation: To convert a liquid to a vapour or a gas requires energy. What this suggests is when sweat on your skin or moisture in your clothing evaporates, this evaporation draws heat away from your body. This is named evaporative heat loss.

Evaporation is a really effective mechanism for dispersing 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, extremely rapidly. Hence, it is vital that you do all that you can to stay dry while in the outdoors.

Your first line of defence agains this kind of heat loss is effective waterproof clothing to stop rain, and other water, getting into your clothing. But it’s not just about stopping water getting in; you must intend to decrease the quantity of sweat in your clothing. When you exert yourself, getting wet from the inside can be a more serious issue than water coming in from the exterior of your clothing. Breathable fabrics that allow perspiration to permeate through will provide help to an extent but if you’re working hard and producing lots of heat, 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 reduce sweat by adjusting layers, particularly taking layers off before starting exercising. Ventilation also helps – open up front zips, reveal the neck, etc. Adjust your clothing as necessary during exercise. You may regulate our activity level; if you’re still getting hot and sweaty in spite of the above measures then you must doubtless slow down a bit and. Pace yourself.

Respiration (breathing) : As you breathe in cold air it is heated before it gets to your lungs. You then breathe out warm air and you are actually losing heat each time you breathe. There isn’t anything 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 through breathing is comparatively irrelevant.

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 great outdoors, it should assist you in staying safe and less likely to suffer from hypothermia.

Paul Kirtley teaches bushcraft and survival skills. Paul is passionate about nature, wilderness and remote travel. This is something that comes across exceedingly clearly on his bushcraft courses.