The Aleut and Inuit have many names for snow; to one whose world is made up of snow, it is important to distinguish between the various forms.
The best types of snow to use for building an igloo are snow that has been blown by wind (which tends to compact and interlock the ice crystals) and mature snow (which tends to stick together). The hole left in the snow where the blocks are cut is usually used as the lower half of the shelter, which serves as a cold-air sump. A short tunnel is constructed at the entrance to reduce wind and heat loss when the door is opened. Because of the excellent insulating properties of snow, inhabited igloos are surprisingly comfortable and warm inside. A single block of clear ice can be used for a light window. Natives used skins as door flaps. When used as winter shelters, igloos had beds made of snow, covered with twigs and caribou skins.
The igloo is unique in that it is a dome that can be raised out of independent blocks leaning on each other and fit together without any supporting structure during construction. A properly built igloo will support the weight of a man on the roof. In a traditional Inuit igloo, the heat from the kudlik (stone lamp) can slightly melt the interior surface, and this melting and refreezing forms a layer of ice that increases the strength of the dome.
The sleeping platform is raised and tends to hold heat generated by a stove, lamp, or inhabitants. The Central Inuit, especially those around the Davis Strait, lined the living area with skins, which could increase the temperature from just above freezing to a temperate 50-68 degrees Fahrenheit. For the 1922 documentary Nanook of the North, an Inuit named Allakariallak built a large family igloo as well as a smaller igloo for sled dogs, using an ivory knife to cut and trim snow blocks, as well as the clear ice for a window, in about an hour. That igloo would house five people.
The usefulness and structural integrity of the igloo depends on very specific design principles. The layout is based on sound architectural precepts, and the methodology and sequence of construction allow it to be erected by one man.
Building a quinzhee
The snow used for a quinzhee is not as particular as for an igloo; it just needs to be of such a consistency that it will pack. An OK quinzhee is also more readily built by a rank amateur, although it is not as suitable for permanent shelter, nor can it be safely built as large as an igloo. Although conceptually similar, a quinzhee is less sturdy than an igloo but can be a favorable tradeoff where there is no igloo-suitable snow. A shovel is not an absolute necessity, but you will need something better than hands to scoop, move, and pack snow.
The method of construction is to pile the snow in a solid heap to the outside dimension of the quinzhee, which is shaped similarly to an igloo but with a more pointed dome, for a hasty shelter about 6 feet high. When within a couple of feet of the outside dimension, put on a layer of marking sticks or dirt, and from that point on the snow must be packed on as tightly as possible. The pile is then left to harden and form new crystals, depending on conditions, in three to eight hours.
When the snow has set up, excavate out the interior to the marking layer of sticks or dirt. A smaller hut-type shelter is more practical as it conserves heat. If you are building alone, it is important to stay on your knees rather than digging from a prone position, in the event of a cave-in. A good method of excavating the interior is to define a block or chunk of snow with the shovel or expedient tool and pry it free. Excavate an interior corridor front to back and then dig out the sides.
This type of structure will not support the weight of a man, but there is enough weight in the snow to suffocate a man, just as in an avalanche, so build no larger than necessary, and be sure snow has properly set. Leave the sides thick because if you accidentally breach the side during excavation, it can all come down. If the snow is at all slushy, it is not suitable for a quinzhee.
I have seen one-man shelters built from the wet snow of the Pacific Northwest by rolling it into balls as if to make a snowman, and stacking these in rows waist high and body wide, to a point in the middle, or building a roof of forest material and covering it with snow.
Digging a snow cave
A snow cave, given the right kind and shape of snow, can have thermal properties similar to an igloo and is particularly effective at providing protection from wind as well as low temperatures. A properly made snow cave can be 32°F or warmer inside, even when the outside temperature is minus 40°F. As seen in the illustration from a Department of Defense manual, a snow cave is constructed by excavating snow so the entrance tunnel is lower than the main space, to retain warm air. Construction is simplified by building it on a steep slope and digging slightly upward and horizontally into the slope. The ceiling is domed to prevent dripping on the occupants. Adequate snow depth, free of rocks and ice, is needed (4 or 5 feet). The snow must be compact or consolidated naturally so that it retains its structure. The walls and roof should be at least a foot thick. A small pit may be dug deeper into one part of the cave floor, preferably near the entrance, to provide a place for the coldest air to settle. The entrance may be partially blocked with chunks of snow to block wind and retain heat, although it is vital to prevent drifting snow from completely plugging the entrance, as ventilation is crucial in a confined space.
This is another instance where a digging tool of some sort is vital, as snow soft enough to be scooped out by hand is probably too soft to safely maintain its shape.
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Excerpted from Building Bare-Handed Survival Shelters with permissions from Ogden Publications.