About Masonry Heaters
“Why are Masonry Heaters special?”
Masonry Heaters use hidden channels to route your fire's warmth through heat-absorbing refractory. This heat is then slowly released as consistent, comfortable, radiant warmth for 12-24+ hours.
“What do Masonry Heaters look like?”
Although a Masonry Heater can look very much like a traditional fireplace, they have many unique features that allow them to have exceptional design flexibility. Heated Hearths and Back Rests; the use of stone, tile, stucco, or brick can make a masonry heater functional like furniture and beautiful like artwork.
“Are Masonry Heaters good for
the earth?”
Masonry heaters are exempt from EPA certification due to their “inherently clean-burning” nature. With firebox temperatures exceeding 1500°F and a short burning period of roughly 2 hours, there is minimal opportunity for creosote formation or incomplete combustion.
Or, to put it in scientific terms: Post-2015, EPA-certified wood stoves cannot release more than 2.5 grams of particulate matter per hour. Most masonry heater kits tested in 1991 by OMNI-Test Labs released about 0.9-1.9 grams per hour; beating modern standards decades ahead of their time.
“What is the technical definition of a masonry heater?”
A masonry heater is a site-built or site-assembled, solid-fueled heating device constructed mainly of masonry materials in which the heat from intermittent fires burned rapidly in its firebox and is stored in its massive structure for slow release to the building. It has an interior construction consisting of a firebox and heat exchange channels built from refractory components.
Specifically, a masonry heater has the following characteristics:
a mass of at least 800 kg. (1760 lbs.)
tight fitting doors that are closed during the burn cycle
an overall average wall thickness not exceeding 250 mm (10 in.)
under normal operating conditions, the external surface of the masonry heater, except immediately surrounding the fuel loading door(s), does not exceed 110 C. (230 F.)
the gas path through the internal heat exchange channels downstream of the firebox includes at least one 180 degree change in flow direction, usually downward, before entering the chimney
the length of the shortest single path from the firebox exit to the chimney entrance is at least twice the largest firebox dimension
The above definitions were unanimously passed at the 1998 MHA Annual Meeting. Site-built masonry heaters in the United States are required to conform to ASTM E1602. Some manufacturers of masonry heater kits opt to certify their products according to applicable UL Standards for fireplaces rather than adhering to ASTM standards.
About the Masonry Heater Association
The Masonry Heater Association (MHA) brings together builders, manufacturers, designers, and homeowners dedicated to the art and science of masonry heaters. We have a passionate, diverse community that values craftsmanship, sustainability, efficiency, and building the best way to heat homes that will ever exist. We also provide certification services for building masonry heaters.