I have a below ground basement which is always cold unless you turn the heat on. Even on a warm summer day you need to turn on the heat to bring it up to a comfortable temperature. It's well insulated, but the sun doesn't hit any of the wall to warm it up.
As I crawled around in my attic the other day the heat was almost unbearable. It was 30 degrees outside and must have been 45 in the attic. I was thinking to myself, why can't this warm attic air be used to heat the basement? I think all you would need is a vent running from the attic to the basement with a fan pumping the air through it. The drawbacks I could see to this system are that there is fiberglass dust in the attic, the system would only work in the summer, and the air in the attic seemed to smell funny, although it may have just been the heat.
Has anyone ever tried to implement such a system?