Loose snow, particularly, being composed of air pockets, can serve as a good insulator.

If nothing else, he thought, ice was a good insulator.

Air is a good insulator and has a very low heat capacity.

Now, add to that the fact that ash is a very good insulator.

"We found, as we had predicted, that space is a good insulator in and of itself."

The frame members are good insulators, so condensation is not a problem.

So the plastic is there because it's a good insulator.

Its chemical structure, for example, indicated that it should be a good electrical insulator.

In this case air has the advantage of being a good insulator too.

In any case, little of the interior heat reaches the surface because "the earth is such a good insulator," he said.