Energy Efficient Rumford Fireplaces
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Many clients tell me that they appreciate the charm of an authentic masonry fireplace, but they are concerned about designing one into their new due to the poor energy performance of a fireplace compared to other wood-burning appliances. With traditional fireplaces, the quantity of heat that escapes up the chimney can exceed the heat that is delivered to the interior. Interestingly, there is a traditional fireplace design which goes a very long way in solving this problem. Invented by a Count from Bavaria in 1796, this special fireplace design offers sizzling efficiency.
The Rumford design has been rediscovered by many masons and builders in recent years and has become an increasingly popular alternative in America. As a practicing , New Mexico, I prefer to incorporate Rumford’s design into my projects whenever possible.
Count Rumford left his Bavarian home for a life in the new American colonies. His loyalty to the British government however forced his hasty retreat back to Europe. Fortunately, the Rumford design became known on both sides of the ocean.
This somewhat forgotten design differs from conventional fireplaces by subtle changes in its geometric proportions. Rumford discovered that if he made the firebox shallower and if he set the sides at a wider angle, then heat would be more effectively radiated into the room. Instead of a low rectangular opening, Rumford fireplaces have a taller, nearly square shaped opening. This added height also contributes to efficient transfer of energy.
The above diagram indicates dimensions for constructing a Rumford fireplace. Ideally, the depth of the Rumford firebox should be at least 4” shallower than what is shown above for best performance. The diagram reflects standard building codes which in most areas (inexplicably) require 20” overall depth for any fireplace. If local codes and building officials will allow it, 16: would work much better. Building codes sometimes also address the throat size which in the case of the Rumford design is quite narrow. So it will be necessary to consult with local building inspectors before constructing this kind of fireplace. The unusual throat size also may require a custom damper. As an alternative to a damper located at the throat, I like to just leave the throat open and to install a chimney top damper. This kind of damper is operated with a chain which runs down the chimney to the firebox. One manufacturer makes available special dampers and other accessories for constructing a Rumford fireplace.
When Thomas Jefferson constructed Monticello, he specified that the fireplaces would be the kind that Count Rumford had invented. At that time, these fireplaces were more efficient than any type of heating device except the Franklin stove (yes, Benjamin Franklin). It is a mystery why Rumford fireplaces are not more widely specified by today’s architects and homebuilders.
By: Greg Allegretti, AIA
The Rumford design has been rediscovered by many masons and builders in recent years and has become an increasingly popular alternative in America. As a practicing , New Mexico, I prefer to incorporate Rumford’s design into my projects whenever possible.
Count Rumford left his Bavarian home for a life in the new American colonies. His loyalty to the British government however forced his hasty retreat back to Europe. Fortunately, the Rumford design became known on both sides of the ocean.
This somewhat forgotten design differs from conventional fireplaces by subtle changes in its geometric proportions. Rumford discovered that if he made the firebox shallower and if he set the sides at a wider angle, then heat would be more effectively radiated into the room. Instead of a low rectangular opening, Rumford fireplaces have a taller, nearly square shaped opening. This added height also contributes to efficient transfer of energy.
The above diagram indicates dimensions for constructing a Rumford fireplace. Ideally, the depth of the Rumford firebox should be at least 4” shallower than what is shown above for best performance. The diagram reflects standard building codes which in most areas (inexplicably) require 20” overall depth for any fireplace. If local codes and building officials will allow it, 16: would work much better. Building codes sometimes also address the throat size which in the case of the Rumford design is quite narrow. So it will be necessary to consult with local building inspectors before constructing this kind of fireplace. The unusual throat size also may require a custom damper. As an alternative to a damper located at the throat, I like to just leave the throat open and to install a chimney top damper. This kind of damper is operated with a chain which runs down the chimney to the firebox. One manufacturer makes available special dampers and other accessories for constructing a Rumford fireplace.
When Thomas Jefferson constructed Monticello, he specified that the fireplaces would be the kind that Count Rumford had invented. At that time, these fireplaces were more efficient than any type of heating device except the Franklin stove (yes, Benjamin Franklin). It is a mystery why Rumford fireplaces are not more widely specified by today’s architects and homebuilders.
By: Greg Allegretti, AIA
Posted by : Greg Allegretti
@ Jun 15, 2011
