quality:correction
Building methods

The snow used to build an igloo must have enough structural strength to be cut and stacked appropriately. The best snow to use for this purpose is snow which has been blown by wind, which can serve to compact and interlock the ice crystals. Snow that has settled gently to the ground in still weather is not useful. The hole left in the snow, where the blocks are cut, is usually used as the lower half of the shelter.

Snow's insulating properties enable the inside of the igloo to remain relatively warm. In some cases, a single block of clear freshwater ice is inserted to allow light into the igloo. Igloos used as winter shelters had beds made of loose snow, skins, and caribou furs. Sometimes, a short tunnel is constructed at the entrance, to reduce wind and heat loss when the door is opened. Animal skins or a snow block can be used as a door.

The igloo is architecturally unique in that it is a dome that can be raised out of independent blocks leaning on each other and polished to fit without an additional supporting structure during construction. An igloo that is built correctly will support the weight of a person standing on the roof.

Traditionally, an igloo might be deliberately consolidated immediately after construction by making a large flame with a kudlik (qulliq, stone lamp), briefly making the interior very hot, which causes the walls to melt slightly and settle. Body heat is also adequate, although slower. This melting and refreezing builds up a layer of ice that contributes to the strength of the igloo.

The sleeping platform is a raised area. With warmer air rising and cooler air settling, the entrance area acts as a cold trap whereas the sleeping area will hold whatever heat is generated by a stove, lamp, body heat, or other device. The Central Inuit, especially those around the Davis Strait, lined the living area with skin, which could increase the temperature within from around 2 °C (36 °F) to 10–20 °C (50–68 °F).