engineering question #666

Angelo, a 12 year old male from Mississauga asks on February 19, 2002,


Why is styrofoam a good insulator?

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the answer

Barry Shell answered on February 20, 2002, A:

Two reasons: it has a low coefficient of heat transfer, which means it does not conduct heat very well. And secondly, it is lots of air bubbles (foam) trapped in little cells, and this also does not transfer heat well. The same principle works with down quilts, double pane windows, etc.

For heat to move from one place to another it needs to travel through some kind of material. (Heat can also move by radiation and no material is required for radiation to work, but that is a different story, and little or no radiation--that is: light--gets through the styrofoam.) Metal is one of the best heat transfer materials. If you warm up one end of a piece of copper, the other end will get hot pretty fast. Air is one of the worst heat transfer materials. If the air is not moving (as in a bubble inside styrofoam) hardly any heat can get across it. So it makes it very very hard for the heat to get across the bubble, and since styrofoam is mostly bubbles, it's hard for the heat to get from one side of the styrofoam to the other.

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