"Jonathan Grobe" wrote in message
...
I have a traditional brick chimney which I no longer
use as I have switched to a high efficiency propane
furnace (so the smoke goes out through a small pipe).

Any estimates of how much heat loss I am having
(brick having a low R-value) and what I should about
it? (I don't think I have the energy to remove it).

Insulate around it as best you can and be sure to cap the top and block the
base to prevent air from moving in or out.