We are new owners of an 1840's farm house with fireplaces in every room. We have discovered that one of the fireplaces (above the furnace) has been altered to act as the flue to the furnace. A hole has been cut in the stone floor of the fireplace area and the the furnace exhaust piped into the ash bin in the basement so that the exhaust will rise up through the hole above and up the fireplace flue. The chimney has been lined sometime in the past with a clay liner and appears to be in fairly good shape. We originally planned to convert the fireplace back to a usable fireplace. We have had both a chimney sweep and a furnace man look at the situation. The furnace man has recommended that we vent the furnace out a basement window with a fan assist (for $3-4,000). We could then convert the fireplace back to a coal fireplace or add a wood stove in that room. The chimney sweep wants to put in a liner (for $1,200 +) to make the chimney safer. Any feedback would be appreciated. Before we invested so much in either option we wanted to get some second opinions.