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A Good Manual for Cold Weather builders ~

A Masonry Stove Classic is once again available

How about efficiencies of 85-90% from a wood-burning masonry stove? Enter the manual "Russian Fireplace Demonstrations and Workshops" by Jay S. Jarpe, research engineer, May 1981. Long out of print, this approximately 90 pp. manual ( 8 1/2" x 11") covers the design, construction, and thermal performance of a type of European masonry stove known in Russia as a Grubka. In 1980, an innovative New Mexico adobe mason, Robert Proctor, received a State grant to construct eight of these stoves in Community and Senior Citizens' Centers at Taos, Nageezi, Santa Fe, Las Vegas, Albuquerque, Willard, Roswell and Silver City, New Mexico. Elevations ranged from 7000' to 3500'. Efficiencies ranged from a low of 86% at Silver City to a high of 89% at Willard. These are much higher efficiencies than can be attained by most metal stoves available on the market today.

An overall view of an installed Grubka - masonry stove for adobe houses - adobe fireplaces
An overall view of an installed Grubka.

Readers are familiar with these stoves as advertised in magazines such as Fine Homebuilding or This Old House. They are usually imported "prefab" models, are too small to heat larger spaces and they aren't cheap. The shortfall is that it's not easy to find anyone that knows how to build one, or to find a set of plans to build one. With this manual, you'll find all of the thermal documentation as well as the plans. Moreover, there are figures plotting temperature changes over time in all eight varieties of the stove. The text gives the builder plenty of direction about placement of rebar, type and strength of masonry mixes and pitfalls to watch out for.

The project was sponsored by The University of New Mexico, and funded through the New Mexico Energy Institute. Built of block, adobe, brick and other masonry, the eight stoves were fitted with thermocouples to measure their thermal performance and to determine how heat traveled through them. To better define the stove, we quote from the manual:

"The Russian fireplace is a high-mass masonry wood stove with a circuitous flue that allows the heat in the flue stream to be transferred to the masonry for later release to the area to be heated. Variations of this type of wood heater are common in colder European climates. It could be a Finnish, Swedish, Polish, Austrian, German or Italian stove. The Mennonites of Nebraska built a labyrinth flue heater that burned grass or straw. All varieties have high masonry mass, long flow path, and resulting high efficiencies in common. The user may gather less wood and tend the fire for only short periods each day to achieve comfortable surroundings. The wood can be scrap limbs or other inferior shapes up to four feet long. Wood with diameters of 2" or less will give the best efficiency."

The above means that owners of these stoves no longer have to purchase "thick" wood by the cord. Salt cedar, or forest slash (often free to gatherers to reduce fire danger), or trimmings from orchards are ideal, as are wood construction scraps.

One of the remarkable features of these stoves is that they are very clean, that is, they burn up all pollutants. When a firing is underway, one can go outside and look at the top of the chimney flue. You will see no smoke, only the shimmering effect of the heat as seen when looking at a mirage. This indicates a flue temperature at around 1100°F. As Jarpe points out,

"Smoke is generally composed of water vapor and tar droplets that condense when they contact the cold air. When the tar is ignited and all water is driven off, and the flue temperature is high enough to be well above the condensation temperature, the smoke visibly disappears. At this point, combustion is nearly complete."

A view of the Grubka's firebox steel door with typical wood fuel of small diameter.
A view of the Grubka's firebox steel door with typical wood fuel of small diameter.

Sections and elevations are provided in the manual at ½" = 1' 0" and cover 25 pages. These include details of foundations, the masonry itself, steel placement, damper assemblies and the design of the steel front door (3/16" hot rolled steel) and its important air inlet ports. 12 pages are dedicated to graphs plotting heat flow through the stoves over time. The remaining text is straightforward and informative.

A difference in building a Grubka as compared to a standard or Count Rumford fireplace is that the Grubka will cost more in materials and time. They are larger, and the entire oven, masonry arches and flue path must be constructed of firebrick, using fireclay mortar. Concrete block or adobe or red brick may be used in the "shell" surrounding the inner firebrick core.

Add the Grubka Masonry Stove Book to your PayPal Shopping Cart!SWSA sends you this manual in a 3-ring notebook for $27.
(Price includes priority mail to you and all applicable taxes.)

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