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Portage & Main Outdoor Wood Boilers

Masonry Heaters

A century ago, MARK TWAIN declared that a masonry heater could heat a home comfortably all day after one firing, consuming "no more fuel than a baby could fetch in his arms." In comparison, TWAIN called the American wood stove "A terror" that wastes so much wood it makes you "think you have been supporting a volcano".

Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass.
Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass.

Masonry heaters , also known as "Russian", "Siberian", and "Finnish" fireplaces are especially effective in superinsulated buildings, such as The Strawbale House. They produce more heat and less pollution than any other wood or pellet burning appliance. Masonry heaters include a firebox, a large masonry mass (such as bricks), and long twisting smoke channels that run through the masonry thermal mass. Their fireboxes are lined with fire brick, refractory concrete, or similar materials that can handle temperatures over 2000 degrees F. A small hot fire built once or twice a day releases heated gases into the long masonry heat tunnels. The masonry absorbs the heat and then slowly releases it into the house over a period of 12 to 24 hours.

Masonry heaters commonly reach a combustion efficiency of 90 percent. The relatively small, but intense fire also results in very little air pollution and very little creosote buildup in the chimney. Because most of the heat from the fuel is transferred to the masonry and slowly released into the room over the day, this type of heater does not need to be loaded with fuel as often as other types of wood heating appliances.


We chose a masonry heater because of its ability to heat so much space with so little wood. At The Strawbale House, we burn less than two loggers cords per year. Many people in these parts heat with outdoor wood boilers. A conventional house our size (2000 sq. ft.) typically would burn 10 to 12 loggers cords using an outdoor boiler. In 2008-09, we could buy a loggers cord for $70. Not only is our masonry heater easy on our pocket book, but also on the environment. Masonry heaters are the cleanest way to burn wood, their large mass allows a fire to be burnt without dampering, meaning a clean quick fire that burns completely.

Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass. Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass. Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass.
Bake oven faces Kitchen
Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass. Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass.

Our masonry heater is the center piece of our 2000 square foot home. Being in a central location allows the heat to radiate evenly throughout the house. Radiant heat is the most comfortable and healthy type of heat, the masonry heater is like having the sun in the center of the house. Our firebox faces the living room so we can enjoy the aesthetics of the intense and dramatic fire. We also have a bake oven that faces the kitchen for convenience.

Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass. Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass. Masonry Heaters, Russian, Siberian, or Finnish fireplaces, in superinsulated buildings like Strawbale House, integrate masonry mass, thermal mass.
Construction of our Masonry Heater

Stove Type  Particulate Emissions (g/kg)  Carbon Monoxide (g/kg) 
Conventional Woodstove  15.3  115 
Phase II Pellet Woodstove
(most efficient) 
2.1  20 
Heat-Kit-22 Masonry Heater
w/bake oven  
0.68  18