Snow's trapped air turns igloos into insulated refuges
An igloo is a snow-block shelter most famously linked to Inuit life, though traditionally only some Arctic peoples used them. Air pockets in snow insulate so well that body heat can make interiors surprisingly mild—the so-called igloo effect. In Inuit languages iglu can mean any house, not only a snow one.
Snow igloos were traditionally built only by Inuit in two regions, Canada's Central Arctic and Greenland around Qaanaaq; elsewhere Inuit built houses of whalebone and hides and banked snow around them for insulation. Outside the Arctic the word means a domed snow house, but in Inuit languages iglu covers tents, sod houses, driftwood cabins and modern buildings too, and it is the term Nunavut's government uses. Speakers around Igloolik reserve a separate word, igluvijaq, for the snow version. With the outside air at minus 45 degrees Celsius, body heat alone can hold the inside between minus 7 and 16 degrees.
There were three traditional sizes. Small ones sheltered hunters for a night or two, sometimes out on sea ice. Mid-sized ones housed one or two families in a single room, clustered into villages. The largest were usually built in pairs, one for living and one for occasions, and could have five rooms holding twenty people; several smaller igloos joined by tunnels could serve for feasts and dances.
The dome is not a hemisphere but a catenary, closer to a paraboloid, which keeps the ageing, settling snow almost entirely in compression so it does not buckle. Builders need wind-packed snow whose crystals interlock; soft snow that fell in still air is useless. Blocks are cut with saws and long knives, first as four-sided shapes and then trimmed to five or six sides so they lock together, rather like Inca masonry, and the pit left by cutting becomes the lower half of the room. No scaffolding is needed, and a well-made igloo can bear a person standing on top. Over time it sinks as the snow slowly creeps.
After building, a hot flame from a stone lamp called a qulliq briefly melts the inner walls, which refreeze into a strengthening glaze. A pane of clear freshwater ice can admit light, a short entrance tunnel cuts drafts, and the raised sleeping platform holds warm air while the low doorway traps cold. Skin linings used by Central Inuit near Davis Strait could lift inside temperatures from about 2 degrees to 10–20 degrees.
Source: Igloo
