Imagine a six-inch layer of fiberglass insulation in your attic. Now imagine ten inches of fresh snow. In terms of insulating ability, they're about equal because snow is actually a pretty good insulator. In fact, a thick layer of fresh snow on your roof might even save you money on your heating bill, especially if you donít have much attic insulation.

The reason snow is a good insulator is because there's lots of air in snow - in fact, fresh, uncompacted snow might be 90% trapped air. And air is simply not a good conductor of heat.

The insulating properties of snow help explain why, on a really cold day, you can actually warm up by digging down into a deep snowpack. The ground also can provide a small amount of heat, so the temperature right where the snow and ground meet can be about 32oF. Looked at another way, a snowpack prevents the ground's warmth from getting to the atmosphere, so the air above a snowpack can get pretty cold at night. In fact, once a snowcover is laid down, nights can easily be 5 to 10oF colder than if the ground was bare.

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