WE are going through the same issue, we have a flue lined block chimney. I
wanted to use it for the woodstove. We can't because our furnace also uses
the chimney. But if I purchase a direct vent furnace then I can use the
chimney. We would be running the stove pipe up the chimney and this would
cause NO problems. But you still have to maintain the stove pipe once a
year. See if I run the stove pipe up the chimney I can save a bundle of
money, if I have to run stove up along side the chimney I would have to buy
double walled chrome pipe, and thats 85 bucks a 3' piece. Regular pipe is
only about 10 bucks a piece.
You do the math, furnace would be about 500 more or stove pipe would be
about 1300 more. Hmmm

Searcher