Installing a Fireplace and Heating With It

Here's an article from Ken Kern's Owner-Built Home and Owner-Built Homestead, great advice on installing a fireplace and heating with it.


| March/April 1971



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Cross-section illustrations show how a heat-circulating fireplace works.


ILLUSTRATION: MOTHER EARTH NEWS STAFF

No major stretch of the imagination is required to see the status of the fireplace in relation to building site and indoor climate. Given the proper set of climatic circumstances, a well designed fireplace may serve as the sole heating plant. Some experimental fireplace units recently built in England have a reputed 80% efficiency. A Heat Circulating type of fireplace—now becoming more prevalent in this country—barely achieves an efficiency of 40%, and conventional open hearth units give off less than 25% of the heat content of the fuel consumed. With the conventional fireplaces, half of the heat content is lost to the atmosphere in the form of chimney gases. Another one-fourth is conducted directly into the surrounding masonry. An even greater loss occurs when the fireplace is located on an outside wall.

But a fireplace can have a significance to site and climate over and above the pure economy of indoor heating. Symbolically the fireplace belongs more in the realm of the building site—the landscape garden plan—than it does to the house proper. The Chinese have a point here. The house symbolizes the feminine (Yin) principle. As a container, it is hollow, womb-like, commodious and warm; it is run, managed, and cleaned by women. But the site upon which the house is placed contains all the principles of masculinity (Yang). The dark, passive, submissive character of the house is contrasted to the bright and forceful elements of the open landscape. And the most obvious phallic symbol is of course the chimney. Man "tends" his symbol by insisting (as he usually does) on making the fires—even if he does nothing else in the house. Any observant architect will witness the fact that it is more often the husband than the wife who is concerned with the design and eventual "looks" of the fireplace.

I have personally found that more freedom in design can be executed and accepted in the landscape plan and in the fireplace design than in practically any other component of the house. Clients will approve contemporary line and form in their gardens and fireplaces, but reject the same principles of good design when applied to the house proper! This fact gives me reason to expect better results—both functionally and "esthetically"—from the fireplace than from the room in which it is to be placed.

Unfortunately, most of the technical improvements in fireplace design have not yet filtered down into common usage—and this in spite of the fact that improvements occurred as far back in time as 1624, when Louis Savot invented the first Heat Circulating fireplace. His unit was installed in the Louvre, in Paris, and became the direct prototype of Ben Franklin's 1742 "Pennsylvanian Stove." The 1624 French fireplace achieved from 30 to 45 percent more efficiency than most American tract-home fireplaces of today! Savot surrounded the grate with a metal air chamber which had warm air outlets above the fire opening. He also supplied the fire with air from under the floor. Thus room drafts were reduced and combustion efficiency further improved.

Early Fireplace Design

Few people are aware of it, but practically all of the technical features of Franklin's Pennsylvanian Stove were copied from earlier inventors. Savot's concept of pre-heated draft was employed by Franklin with little change in design. Prince Rupert's descending flue, invented in 1678, was also applied on the early Franklin stoves. The smoke rose in front of a hollow metal back, then passed over the top and down the opposite side. Then, at the same level as the hearth, the smoke ascended the flue. Ducts, similar in design to those invented by Nicholas Gauge in 1716 were also incorporated in the Franklin stove.

A noteworthy development of the open fireplace was started in 1796 when the Englishman, Count Rumford, published his comprehensive essay on "Chimney Fireplaces." His main contribution was in the alleviation of smoking chimneys. One fault, he correctly asserted, was due to too large a chimney-throat. Rumford also introduced the inclined fireback, which increased fireplace efficiency by providing a greater radiation area. For the purpose of breaking up the current of smoke in the event of chimney down-draft, the back smoke-shelf of Rumford's improved fireplace ended abruptly—a practice strictly adhered to by fireplace masons to this day.





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