The fireplace invented in 1796 by Count Rumford is a great improvement on traditional fireplaces. Rumford’s design was widely used from the time of its invention through the middle of the 19th century, and they are still poupular today. Rumford fireplaces are tall and shallow to reflect more heat, and they have streamlined throats to eliminate turbulence and carry away the smoke with little loss of heated room air
Back in England, Rumford applied his knowledge of heat to the improvement of fireplaces. He made them smaller and shallower with widely angled covings so they would radiate better. And he streamlined the throat, or in his words “rounded off the breast” so as to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…”
The objective is to reflect or re-radiate as much heat out of the face of the fireplace as possible. It doesn’t hurt to whitewash the firebox or to insulate behind the firebrick. It does hurt to cover the opening with glass doors, which cut about 80% of the infrared radiation.Tall, wide shallow fireplaces [the Rumford design] tend to smoke. The other half of Rumford’s genius is his intuitive understanding of fluid dynamics – way ahead of his time. By rounding the breast to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…” he essentially created a venturi, a nozzle, like an inverted carburetor, that shot the smoke and air up through the throat into the receiving smoke chamber.
Because the true Rumford design is based on the science of airflow, it does not smoke. If you have a Rumford-like fireplace that does tend to smoke, something is wrong: either it’s a pseudo-Rumford with a bad throat design, or the throat’s obstructed or has been damaged. True Rumford fireplaces simply do not smoke—that’s why they were so popular.
The fire in a Rumford fireplace is laid with a large horizontal log at the back and smaller logs placed vertically, leaning over it.