"Buck Turgidson" wrote in message news:hej092-
Just curious, is your chimney on the main or upper level? I have a
fireplace in a basement rec-room, and have assumed heatloss wasn't too
bad,
since it is in a basement. Maybe I should re-think that.

Besides wind effects that may go right down the flue, much of the heat loss
is due to a cold chimney connecting to a warm room, at any level of the
house. The more chimney length is exposed, or greater height above the roof
line, the greater the cold transfer into the flue. Cold air is denser than
warmer room air, so the air sinks rapidly and spreads into the lighter
density, warmer room air, forming a cold layer in the bottom third of the
room - right where you don't want it!