Igloo effect

The Igloo effect refers to the phenomenon that allows igloos and similar structures to remain warm on the inside, despite being made of snow and located in frigid environments. The effect is primarily due to two factors: insulation and body heat.

Description
An igloo constructed with snow blocks will thermally insulate its interior from its exterior. It is known that, whilst snow itself has a temperature below the freezing point of water 0 C, it has excellent thermally insulative properties as it consists of air pockets trapped between ice crystals. A well constructed igloo can keep an average temperature of 16 C if heated internally only by body heat. However, if the blocks are too thick, they can cause excessive heating and risk melting. Several factors affect the thermal characteristics of igloos, including snow conditions, igloo size, structure, and arrangement. For example, a high dome igloo has a higher workbench temperature than a low dome igloo. Also, smaller igloos require less heating than larger ones to achieve the same temperature level.

Examples

 * In 2012, a Swedish man, trapped in his car for two months, had been insulated from the -30 C weather by snow which had created an igloo around his vehicle. He made a full recovery.