During my stint as a staff member at the Cob Cottage Company, I was responsible for building three Rumford fireplaces. Within open fireplace design, the Rumford fireplace offers the greatest efficiency in terms of how much heat actually radiates into the room. The Rumford design is characterized by a shallow firebox and a tall and open fire back which throws the heat into the room rather than straight up the chimney.
These Rumford fireplaces are almost entirely built with cob, a sculptable combination of clay, sand and straw. The Cob Cottage Company, amongst other things, is a laboratory for simplicity… so only the hearth and a couple of courses on the inside walls of the fireplace are made out of fired brick. The rest, including the throat, smoke shelf and chimney transition are all sculpted in the same way that one would sculpt a large ceramic vessel.
The Ridge House Rumford:
The new dining room Rumford (not yet plastered):
The Rumford in the Castle: