Building an Igloo
The following is reprinted from «The Complete Wildnerness Training Guide» written by Hugh McManners and published by Dorling Kindersley.
From Chapter Three, «Living In The Wild»
Provided temperatures remain below 32 degrees F, constructing snow shelters is relatively easy. Sheltering from the wind is the first priority, since the wind can drastically decrease the air temperature. Temperatures below 14 degrees F become increasingly unpleasant, so that it becomes necessary to construct shelters in which heat can be retained extremely well. These can range from a simple, hollowed-out heap of snow to an igloo, which can take a few hours to construct. In a long-term shelter, such as an igloo, heavy, cold air can be diverted away from the occupants by digging a cold sink to channel the air down and away from the shelter. It is important to allow for adequate ventilation in all snow shelters in order to prevent suffocation.
1. Cut blocks from dry, hard, hard snow, using a snow saw or large knife. Each block should be about 3 ft. (1m) long, 15 in. (40cm) high, and 8 in. (20cm) deep.
2. Form a circle with blocks around the hole created where you cut the blocks. Cut the circle in a spiral from the top of the last block to the ground ahead of the first block. This will make it easy to construct a dome.
3. Build up walls, overlapping the blocks and shaping them so that they lean inward. Cut a hole under the wall for the cold sink and entrance. Put several blocks along one wall as a sleeping platform
4. The last block must initially be larger than the hole. Place the block on top of the igloo, then, from inside, shape and wiggle it to slot exactly into the hole.
5. Hot air from your body and stove rises and is trapped inside the dome. Cold air falls into the sink and flows away to the outside. It is essential to cut ventilation holes in the walls with an ice ax.
Finished Igloo. With warmth inside the igloo, the surface of the walls will melt and freeze over, to form a smooth, airtight ice surface. The roof over entrance tunnel prevents snow from blowing into igloo.
WARNING! It is vital to make at least one airhole in the roof to avoid suffocation. The igloo will get very warm inside with heat from your body, even if it is cold and windy outside. Without ventilation, lethal carbon dioxide will build up. Also, the use of stoves in an enclosed shelter is not recommended due to dangerous build-up of carbon monoxide.