Hardly a year goes by on Earth without some of that interior heat forcing its way to the surface in a major volcanic eruption.

All these are long-observed signs of the planet's interior heat and stresses.

But they did not prosper in the interior heat.

Perhaps it came about when the interior heat melted underground ice.

They also have an insulated core to retain interior heat during the cold months.

Install this with the vapor barrier facing down, toward the source of interior heat in the winter.

But now the interior heat is going somewhere, somehow.

"Then there must be a lot of interior heat waiting to get out," Percy said.

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

Insulation, however, will only keep interior heat from passing through solid materials like wallboard or wood.