A lesson in common sense
I have been asked so many times in my 35+ years in the masonry business, as to why some fireplaces smoke and others do not? And how does one get more heat from a fireplace? Over those years I have formulated an answer that started from a cheeky “stop using damp wood” to a well informed description of what constitutes a well built fireplace that doesn’t smoke and gives the best heat efficiency, and that is a description of the “ Count Rumford fireplace” design.
Count Rumford was born Benjamin Thomson 1753 in Massachusetts. Being a loyalist he had to do a quick exit in 1776 (Declaration of Independence) spending the next 9 years in Britain. After receiving a knighthood from King George in 1784 he spent 11 years in Bavaria, where he invented among other things, the relatively clean burning wax candle, replacing the tallow and beef fat ones which smoked and often smelled of rancid fat. It was in Bavaria that he received the title Count of the Holy Roman Empire for his good services. On his return to England he published the book “Of Chimney Fireplaces”1796 and in that year 250 fireplaces were rebuilt to his design in two months. His experiments in the area of heat are well documented and widely respected. His fireplace design though scientifically well proven, is in my mind based on pure common sense, and it works.
In Scotland (the dear land of my birth) coal was the fuel of the day, and the fireplaces were small and only inches deep, however they threw off an amazing amount of heat without smoking. When I look back, I remember them being the little brother of the Rumford design (usually metal inserts) with straight backs and the sides angled quite sharply or rounded.
As previously stated there is a wealth of scientific evidence of why this design works better over more modern ones. However, I’d just like to explain it in simpler terms.
The native Canadians and Americans would build their small fires surrounded by stones in the middle of the teepee. The smoke would rise and go through the smoke flaps unimpaired, and the stones would radiate the heat that they absorbed. I think that these two things are the most important traits of a working fireplace. The construction of the smoke chamber is paramount in importance for the guidance of the smoke to rise up the chimney with the least amount of resistance, all sides must be smooth and steep, and this is achieved by parging the whole inside properly. The firebox should be shallow with a straight back, and the covings (side walls) angled sharply, which has the effect of bringing more of the radiant heat into the room.
I have found that not all tastes, designs and sizes can lend themselves to be a Rumford fireplace, however the design is a proven one, and I’ve been able to adapt the basic principles to many of my projects with great success and customer satisfaction.