How to keep warm with limited use of fire?

Question

The general rule for keeping warm in wilderness in cold climate is to make fire, as big as possible. While being effective, it's not sustainable in longer perspective because it is depleting natural resources very quick. It is also not always possible, for example in subarctic zone, or high in mountains.

What are the techniques to get warm without fire or with limited usage of fire? How to survive not 2-3 weeks as climbers, but the whole winter? What must be taken into account when housing in such conditions, to create housing conditions using as little timber and other burning materials as possible?

Answer 1

An Igloo is an efficient shelter made of snow/ice blocks. At first thought, the snow is cold so how could it keep one warm. The true value is in the insulation. The design creates a small insulating shelter. The cold weather stays out, the body heat stays in. This is part of the reason they are built small, like tents. The small volume is easier to heat by residual body temperature alone. The more people in the structure, the quicker and warmer it will become.

The human body averages 98.6 degrees Fahrenheit (37°C), the reason for hypothermia is the environment is sapping too much of that heat energy away from the body. By creating an igloo or similar structure, it is possible to prevent the body heat from moving too far away. As the body releases heat energy, it becomes trapped in the igloo by the thick snow walls, and builds up. The interior will not reach 98.6, but it is possible to raise it to a much more comfortable temperature than the frigid outside air.

One thing to remember with igloos is that they are cut down into the snow pack, not built on top of it. This allows a smaller surface area presented to the outer environment. Also, the orientation of the door must be taken into consideration. Allowing the cold wind to drive right in through the door is not a good idea.

Further, the snow itself will still be cold to the touch. Proper clothing is essential, the igloo just helps to maintain an environment with a higher ambient air temperature, thereby slowing the rate of heat loss from the human body. Any structure performs the same function, the igloo works with body heat because of its small size compared to the size of the occupants. Obviously, if the igloo is built too large for the number of occupants, it will not be possible to heat with residual heat alone.

Answer 2

A fire is a very inefficient way to get warm and keep warm. However, if your fuel is renewable, and your usage rate is lower than the replenishment rate, there is no sustainability issue.

To make a fire more efficient, use a stove rather than an open fire:

Use a good design, to ensure as little heat goes up the flue/chimney, and as much stays in the room, while venting enough to get rid of the fire's emissions.

To reduce the amount of heat loss, curtail losses from radiation, convection and conduction. To curtail radiation, avoid materials that allow infra-red to pass through them; and prefer materials that reflect it. To curtail conduction, use materials with high insulation values (aka very low U-values) - particularly in warm layers of clothing. To curtail convection, have as little air flow through as is needed to prevent the concentration of pollutants, and to keep carbon dioxide levels down below 1000 ppm. Ideally, have a way to transfer heat from outgoing air to incoming air.

Add a lot of thermal mass, to convert the fire's short burst of high temperature into a long slow burst of lower, more useful temperature.