Heating efficiency: Rumford fireplaces are the best wood-burning high intensity radiant heaters ever developed. They heat people and surfaces like sunshine and like the infrared heaters you see at outdoor restaurants, or in aircraft hangers or UPS garages where it's difficult and inefficient to try to heat air. Rumfords work best in open areas, big rooms with vaulted ceilings or even outdoors. Radiant heat raises the mean radiant temperature of surfaces and makes people feel comfortable at cooler air temperatures, just like the sun, so Rumford fireplaces are a good way to heat even with the windows open in moderate climates like those of England, the west coast or the midwest in the spring and fall. More about radiant heat and efficiency in a tech note.

Draft: Apples to apples, Rumford fireplaces draw better than any other fireplace. The streamlined throat and efficient air flow makes it possible to build the Rumford fireplace opening about a foot taller than other fireplaces. And we do build them tall (usually as tall as they are wide) because we can and because tall fireplaces heat better and look better. Then they don't draw any better than regular low fireplaces. The point, of course, is to heat - not draw better than they need to and waste heated room air. There's a lot more about how fireplaces draw in the JLC article about Rumfords and how they work in very tight houses and what to do to fix "smoky" fireplaces in the "technical Discussion".

The Rumford fireplace works on a different principle. The idea of the plumb fireback and rounded streamlined throat is to let the dilution air flow as a sheet of clean air that keeps the smoke and products of combustion behind it flowing up the fireback. Turbulence is undesirable until the dilution air and smoke enter the smoke chamber flowing smoothly through the narrow nozzle-like throat.

"So what?" you might ask. Well, for starters the Rumford fireplace can be built taller and is more efficient and cleaner-burning.

The Rumford fireplace can be built much taller than a standard fireplace because of the efficiency of the airfoil throat and control of the smoke flowing up the fireback behind the sheet of clean air.

By not mixing the smoke and dilution air more smoke burns in the firebox where it contributes to useful heat rather than exiting the chimney as particulate emissions. The Rumford design increases the "residency time" - the length of time the smoke is hot and in the fire - by about four times compared with the modern fireplace where the smoke is diluted and fire is quenched about 6" over the fuel.

For more on the physics with some test data to back up these claims, read the JLC article about Rumfords.