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?