I’ve mentioned building a masonry heater in a couple posts now, so some of you (especially those in the US) may be wondering what exactly that is. At a most basic level, you can think of it as an extremely large, very efficient fireplace. Basically, it is a large structure that has enough thermal mass to capture the heat of a big fire and slowly radiate it out to the room. To help with this goal, there are a number of internal smoke channels to extract the heat from the burn and in general, the burn itself should occur at such a high temperature that emissions are extremely low.

Given the fact that we have nearly 17 acres of trees, heating with wood has always been something we wanted to do. It also coincides nicely with our goal of self-sufficiency. Mr. BBB researched the options and eventually decided on a masonry heater for a number of reasons, including:

1. When built and used correctly, it is more efficient than even the most efficient wood stove (and vastly more efficient than a fireplace)
2. It has very low emissions of unburned hydrocarbons
3. You only have to fire it once or twice a day for heat instead of continually feeding it wood
4. The surface tends to be warm but not too hot (except for the door of the firebox) which is important given that we planned to have kids (and now do—though they’re not yet mobile)
5. It’s aesthetically pleasing
6. It would give us a large thermal mass which would help in the summer, too, since it can store heat to keep the house cooler

Of course, actually figuring out how to build one was a much greater challenge. There are very few people in the US who know how to build one (other countries, especially in the Nordic region, use them quite extensively). There was certainly no one local—everyone that we talked to just wanted to sell us wood stoves. Eventually, my husband found someone who, though he lived over 300 miles away, was willing to travel to us. Even better, he was willing to spend a few days teaching my husband how to build the masonry heater instead of doing it all himself (and charging accordingly).

Based on what he and Mr. BBB discussed, the mason designed a two-story masonry heater with a heated bench. Basically, the core of the heater was built of firebrick and special castings that would direct the escaping smoke down a channel on the side. It would then enter clay flues that formed the interior of the bench before exiting up the clay flue chimney. We would face the heater in anything we wanted as long as it was at least four inches thick—the mason suggested plaster and CMU bricks as a cheap and easy facing. Of course, we can’t do anything the easy way, so my husband decided to do granite cobbles downstairs, and we collectively decided to do brick upstairs after realizing just how long the granite cobbles took.

Now that it’s done, we definitely appreciate having this heater. Even without running it at full capacity this winter, we saved over $500 on heating and kept the house warmer than we usually do with only electric heat. But I would certainly caution anyone on jumping into a similar project without doing some research. Retrofitting a home for such a device is challenging. For starters, the sheer weight of the masonry necessitates a thicker foundation than is normally poured (we accomplished this by having the contractors cut a hole in the existing foundation and pour a new pad where the masonry heater would sit that was twelve inches thick with half inch rebar six inches on center). Additionally, for maximum efficiency, you want the heater in a central location with no walls between it and the rooms it’s heating, so an open floor plan is ideal. It also has a large footprint, so you need to be prepared to give up the space for it (this is one of the reasons we decided to do it with an addition). But if you can overcome these obstacles, it truly is a beautiful, energy efficient addition to your home that can save you a good deal of money assuming you have a free source of wood.