Some fireplace manufacturers offer "remote zone" capabilities which consist of ducting and a fan to help draw the heat to a remote location. Since the heat generated by an unattended firebox can be irregular, you will want a thermostat in the remote zone to help control temp and prevent overheating like you mentioned. You might also want to add a firebox temperature sensor so that if the fire does die down, your remote fan won't continue to pull cold air into the zone all night.
Normally, the air to be heated is drawn into the fireplace through local louvers or grilles, but to further enhance a circulating effect you can add ducting of modest length to draw the air from the opposite corner of the house.
The most efficient fireplaces and stoves are sealed and draw combustion air from OUTSIDE the home, exhausting the gases up the chimney. I would never try fan circulation with an unsealed unit because of the possibility of poisoning from combustion gases.
Google "EPA stoves" or "EPA fireplaces" to find them.
Google "Quadrafire" for one example of a manufacturer that offers remote zoning options. |