How Igloo's work
What is an igloo?
Before I dive into how an igloo works, first I'll give an outline of what a historically known 'Igloo' is. An igloo is a dome shaped shelter constructed from blocks of snow. More permanent igloos known as 'Eskimo houses' were built out of materials such as wood, stone and sod. However, for emergency and convenience purposes, snow based Igloos were mainly built for temporary uses as a part of survival.
How an igloo works
The three main factors that come into play in terms of the energy transfer within an igloo are:
- Radiation
- Convection
- Conduction
A human body, which acts as a source of heat for the system, radiates body heat which flows around the igloo via convection in which a portion of it gets lost through the igloo walls via conduction. The secret comes from which type of snow is being used. if you were to use regular solid snow for igloo walls, they have good protectiveness against the harsh environment such as wind, however don't offer the best insultation properties and are also very heavy and harder to construct with. Powdered snow in the form of blocks on the other hand is made up of 95% of trapped air which makes it less protective against the environment but in return offers excellent insulation.
Another factor used in the design of the interior of igloos to aid in maintaining warmth is having different levels.
Figure 1 - Igloo interior (Quora)
The figure above is an example of what the inside of an igloo would look like. The hot air inside rises and the colder heavier air when sink to the ground meaning that the upper area is the area that is used for sleeping/eating/general living purposes to stay warm. Occasionally a middle level can be created for having a fire however is not always necessary.
Most effective igloo shape
Unlike how igloos are portrayed in some cartoons, most igloos are not perfectly dome shaped like a semi circle. Igloos are best constructed in the shape of what is known as a 'catenary curve'. This type of shape closely resembles that of a paraboloid and is used due to the nature of the shape being able to with hold the stress and compressive forces before it buckles.
Why igloos are awesome
When we think of trying to stay warm, nothing sounds more contradictory than using ice/snow to do just that. However because of the thermal and structural properties of some specific types of ice, this is a completely valid approach to staying warm using not but the simplest of surroundings. To put this into perspective, the outside temperature could reach as low as -45 degrees Celsius while the inside of an igloo, heated up purely by body heat alone can range from anywhere between - 7 to 16 degrees Celsius.
References
https://www.quora.com/How-does-an-igloo-work
https://www.transun.co.uk/blogs/how-does-an-igloo-work
https://www.youtube.com/watch?v=1L7EI0vKVuU - How An Igloo Keeps You Warm
