Well a Rumford fireplace. To put it simple the most wonderful fireplace in existence! An amazing fireplace actually and there are a couple of masons who are able to build amazing fireplaces of the Rumford design. I sweep a few and can get you in contact with customers where you may be able to view them.
What makes them different? What makes them special? Well a Rumford fireplaces is quite tall and the hearth is much more shallow than a typical fireplace, a design that allows it to reflect more heat into the room. Design wise they also have a very streamlined throat, reducing the air turbulence normally present in a smoke chamber, allowing them to remove less heat from the room as the smoke exists. The Rumford fireplace originated in the 18th century and were quite commonly used as heating appliances at that time. Rumford worked hard designing better fireplaces, ones that would efficiently radiate heat into the room.
Modern fireplaces are built for aesthetics alone without any concern for efficiency or even for the amount of air drawn out of the room. The Rumford can fix this, although getting the local Building Inspector officials onboard is sometimes challenging.