Squam Lakes Natural Science Center Blog

How We Stay Warm and Eat Well with Less Carbon
By Dennis Capodestria and Jenny Highland

Three years ago we decided to replace our wood-burning stoves with a thermal mass masonry heater. For years we’d been tending one or more stoves, trying to maintain a comfortable temperature. The house went from too cold when we came home from work, to uncomfortably warm by bedtime. Of equal concern was the smoke our chimney was emitting for hours at a time. After investigating wood boilers, pellet burners, solar hot water, and other alternatives, we settled instead on an old technology that is simple and reliable (no moving parts or electronics). Masonry heaters have been used for centuries in Russia, Finland, and other cold regions.

Our design includes a large firebox with a bake oven above and a cook top off the side. The structure is built of firebrick channels and chambers all enclosed in two-inch-thick slabs of soapstone. The entire mass weighs about 7,000 pounds – light for a masonry stove but quite adequate for our small house.

Firing a masonry stove takes a different approach than a woodstove. Instead of slow, long-burning fires, the object is to burn hot and fast for clean, efficient combustion. Once the fire is out, a damper closes off the chimney and the heat slowly penetrates through the stone to warm the house. Because heat is released gradually, one or two fires a day maintain an even temperature.

Now when we come home the house is still warm, and at its core is a beautiful blue-gray mass of radiant soapstone. The smoke is so clean it is almost imperceptible, and we don’t have to cut as much firewood. We were able to get rid of two woodstoves and an electric oven. Our new masonry oven, with its constant “free” heat, has changed the way we cook. When hottest, it provides us with pizza, turkey, bread, or pies. As it cools, we cook grains, beans, heat up leftovers, or bake overnight breakfast porridges. In short, life is good…