Masonry heaters are an efficient, sustainable, centuries-old solution.
The custom installation process for masonry heaters is an opportunity for creative design.
Photo by Stuart Davies
You don’t have to wait for technological advances to create an energy-efficient, nonpolluting, convenient, and comfortable method of heating your home. The technology is already here—and has been used to heat the famous Roman baths and warm beds and floors in China and Korea for centuries. Europeans perfected masonry heating stoves 400 years ago, during what we might call the first energy crisis, when it became clear that conservation measures were needed as citizens in growing villages demanded more and more wood for heating and cooking.
In the late 1700s, King Gustav III of Sweden charged two men, F. Wrede and C. J. Cronstedt, with the job of designing an efficient masonry heater. The product of their efforts was an efficient fireplace that is very similar to heaters being built today, says Ken Matesz, a certified heater mason who operates Fountainhead Natural Homes in Swanton, Ohio.
Unlike fireplaces and wood stoves, masonry heaters don’t guzzle wood or suck warm air out of your home and up the chimney, resulting in a net loss of heat. They don’t produce and deposit creosote on the inside of your chimney, creating a fire hazard, nor do they pollute the environment. When used properly, a masonry heater contributes no more pollution than what occurs from wood naturally rotting on the forest floor, Matesz contends.
What is a masonry heater?
A masonry heater is a wood-burning appliance made of solid masonry that acts as thermal mass, which absorbs heat from a relatively short, hot fire, then releases it as slow, gentle radiant heat that lasts twelve to twenty-four hours after the fire goes out. In the United States, masonry heaters usually fall into one of four categories. “Since the concept of masonry heating is of European origin, we tend to group them by characteristics they had in their country of origin,” explains Matesz. “So, we have a Finnish contraflow, a Swedish, a Russian, and the Grundofen. All types have the same general characteristics of high-mass masonry construction, heat exchange channels that make at least one 180-degree turn after leaving the firebox, and stored heat that lasts many hours after the fire is out.” (See “A World of Choices,” page 81.)
Masonry heaters don’t operate like conventional wood burners. First, the firebox—designed to facilitate quick heat—is loaded with fuel (wood), and a fire is started. The fire is burned with plenty of air but with doors closed. A narrow throat above the firebox contributes to fast burning and turbulence. Another chamber, above the throat, swirls and mixes turbulent gases at high temperature, until they are thoroughly consumed. From here, the exhaust circulates through a lengthy heat exchange channel (a sort of prechimney with twists and turns) that draws heat from the exhaust into the masonry mass. Finally, the significantly cooled exhaust exits the system through a relatively ordinary chimney.
“The fuel load burns for about an hour and a half and is allowed to simply burn to ashes, Matesz says. “When there is no more sign of fire, the chimney damper is closed, and when the last coals turn black, all air supplies are 100 percent turned off. A couple hours later the sides of the exterior of the heater begin getting hotter and hotter, usually hitting a maximum of about 150 degrees Fahrenheit. The heat from these warm surfaces is what radiates throughout the whole surrounding living space,” he explains.
Building your heater
In 1994, Matesz helped build a masonry heater at Slippery Rock University in Slippery Rock, Pennsylvania, and in 1995 he built a Finnish contraflow masonry stove in his own home. Matesz and his wife, Nancy, built the central core from standard firebrick and the exterior from solid red brick.
Matesz is one of only about fifty members of the Masonry Heater Association of North America (MHA), a nonprofit organization that promotes the heaters. The MHA also runs a heater mason certification program so that individuals throughout the United States and Canada can find masons well versed in the most up-to-date requirements and methods for building efficient and long-lasting appliances. For a list of MHA-certified members, visit www.mha-net.org.
To build a masonry heater in your home, you need to plan ahead. Materials must be custom ordered to fit the size and design of your home, floor plan, and stylistic preferences. Plan six months to a year in advance, as there are so few certified masons in North America.
Masonry heaters range in price from $5,000 to $30,000, depending on the size and customization. A simple, brick heater designed to heat about 2,000 square feet of living space will cost around $10,000. Options such as heated benches, wood storage areas, unusual shapes, and natural stone veneers will up the price.
Putting a masonry heater into new construction is very straightforward. “You should plan to have the heater centrally located in the home,” Matesz advises. Retrofitting the heaters into existing homes is more challenging, but usually doable.
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