According to the article the igloo can be 4 feet or higher. This means that when you build the igloo it has to either be 4 feet or higher because you want your igloo bigger is so you don't keep hitting your head.If you keep hitting your head then the top of the igloo, the igloo will break. This matters because if you want your igloo to last longer then you might want to build it a little higher so that you don't keep hitting your head!
According to the article, the igloo can't have any holes in it. This means that if you build an igloo the first time and it has too many holes in it then you might have to start over. So when you build your igloo be careful! This matters because if too much warm or cold air comes in, it can make your igloo melt.
Don't forget that if you leave too many holes in the igloo it will cause warm or cold air to come in, and that you want your igloo to be 4 feet so you want hit your head on the top and break it. That is all for today about how igloos work!