In the past, Inuit people of northern Canada built igloos and lived in them during the cold winter months. How can a house of ice and snow keep you warm? The ice blocks out the cold wind. Ice is also good at trapping heat from a candle, small fire, or even from your body.
The heat inside an igloo can make the insides of the walls start to melt. But the outside of the walls is still cold. This makes the walls turn from snow into ice. Ice walls are much stronger. A grown man can stand on top of an igloo without it falling down!
How do you build an igloo? An Inuit builder cuts blocks out of well-packed snow and makes a ring of blocks on the ground. Next, he stacks a second row of blocks on top of the first row. The second row is tilted inward just a little bit. This means that he needs fewer blocks for the second row than for the first. He continues stacking blocks and the walls of the igloo grow. He carefully fits the blocks together so they don’t fall. Finally, he places the last block on the very top of the igloo.

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