A warm house made of snow – how does an igloo work?

10.12.2019

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Culture Story: A warm house made of snow – how does an igloo work?

These houses built with large blocks of pressed snow can be perfect temporary shelters or even someone's home. But how is it possible to keep a structure built of snow warm inside? And why don't it melt? Here are all the answers.

The most effective igloos are build from snow, not ice

When it comes to building a perfect igloo, you can't find a better material than snow. About 90-95% of snow is just air trapped between microscopic ice grains, which means that air from the outside of an igloo can't easily pass through its blocks.

It's all about the shape, which is called a catenoid

Such a shape is perfectly optimized to ease structural tension of the shelter. For a house built from such an unstable material as snow, it's the key point – thanks to its form, an igloo is not falling apart soon after being finished. In a catenoid, all the pressure is compressed toward the sides of the dome, which saves the middle of the ceiling from extra tension.

Why doesn't it melt inside?

Provided temperatures outside are constantly below freezing, a constantly inhabited igloo can last for several months. In fact, an igloo melts, but very slowly – again, thanks to its structure and large mass of the blocks. The inside walls melt slightly, and small amount of water goes down them. As it contacts with the blocks, which sustain the cold from the outside, it very quickly becomes ice. In other words, the walls of an igloo lose heat to the colder air outside.

What is the interior like?

Culture Story: It's very important to create a dip inside — shutterstock

The sleeping area is usually raised, because all the hot air goes up. As the cold air, on the contrary, sinks, it stays down. Thanks to the dip, it moves towards an isolated part connected to the entrance.

Another important thing is a small hole at the very top of the shelter – if you use fire to warm the place up, you need to get rid of the smoke. Even with the fire an igloo won't melt – it is located at the very center of the shelter, as far as possible from the walls.

What's the temperature inside?

Thanks to its wonderful insulation capabilities, an igloo can be be warmed by body heat alone. The temperature inside ranges from 19°F (-7°C) to 61°F (16°C). This may seem cold, but this means that if it's -40°F (-40°C) outside, it's 32°F (0°C) inside your igloo, which is quite impressive.

Would you try to build an igloo? And would you spend a night in a shelter like this?

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38 Comments

Audie Hicks

Built and lived in one for 2 weeks. Winter warfare training in Germany. We were a 2 man team. We had two 3 inch candles for light and warmth. Ate dinner in our skivvies warm as a bug in a rug.

dragondawg

As I've said before, having lived above the Arctic Circle, in a place called Inuvik, Northwest Territory., Now Nunivut. I've watch them build igloos. It is a specific snow that they look for for the construction. When they are out hunting on the ice, they might build one so they can stay longer. When I was there, things were still being done, most of the time, by dog sled. Now they use snowmobiles. They could have over a 200 mile long trap line. Or be hunting seal. The women will start preserving meat, rendering down of any fat for candles and traditional medicines. And they use their clothing as their bedding and blankets. As they are usually made from mink, seal, or rabbit, plus hide that has been tanned from some deer. It really is amazing to see. And I agree Audie Hicks, with just a couple of candles your toastier than most people think.!!

Elaine Bauer

Also, the shape of the interior walls sets up convection; warmth circulates. In elementary school, a bunch of us built a snow fort at recess. We were able to sit in there and take our snowsuits off; it was that warm from the insulation properties of the snow. A self- taught science lesson, it was great fun!