Our house is heated mostly through the solar gain of the southern windows and good insulation and thermal mass. However, once in a while, mostly when it's cloudy, we need a fire for additional warmth.
The wood burning heater is in the living room, but the stove pipe goes through Leo's room before heading outside. We already had a heat exchanger around that stove pipe with a fan on it to keep the upstairs warm, but we have now made it much more efficient.
We removed the stove pipe all together and replaced it with metal box that Abe made. It basically has a huge amount of surface area that the rising heat has to pass through and warm. More surface area=more heat in the room.
It's not yet time to light a fire, though we may have to just to test it out.
One of the things on our list to do for next week is to replace the stove in the living room with a rocket mass heater. Stay tuned.