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Keeping Warm with Our Masonry Heater

A masonry heater uses wood efficiently and can be the primary heat source for your home. Dogs like them, too. Image: Dan Crosby.

Dan Crosby, Local Energy $olutions

We have no oil furnace. Instead, we heat our 1900 sq. ft. home in Bethlehem, NH by burning 3.5 to 4 cords of wood each year in our masonry heater. A masonry heater is an option that I would encourage everyone to consider for a newly constructed home, and it may also be an option for retrofitting an existing home. We rely on our masonry heater to keep our house warm, but many people who have masonry heaters do have another heating system. If they are away for multiple days in the winter, their other system can keep their house warm. Once back home, however, using the masonry heater causes the other system to run much less, or not at all.

So, what is a masonry heater? Its core, which can withstand very high-temperature fires, is surrounded by some type of facing material, such as brick. The exhaust does not go directly from firebox to chimney, but takes a much longer path through heat-exchange channels in the core, thereby heating the large thermal mass of the heater. This heat is then released evenly between the, at most, twice-a-day burns. Depending on the outside temperature, sometimes we burn just once a day. Twice a day is typical for us in midwinter.

A masonry heater offers several advantages. The rapid, hot burn of the wood allows a more complete burn, reducing the amount of wood needed to produce the same amount of heat as compared to a metal wood stove. The hot, clean burn means less frequent chimney cleanings. In 17 years, I have never had to clean our chimney. Also, with the exception of the metal and glass of the fire box door during and right after a burn, the surface temperature of the heater never gets so hot as to cause burns from a quick touch. In fact, it is very pleasant to lean right against the heater during a cold winter evening. Since a glass door for the fire box is common, and a typical burn may last 1.5 to 2 hours before we close our chimney-top damper, we have ample opportunity to enjoy the fire. Masonry heaters are attractive, too. They can look quite different depending upon what material is used for the outer layer. Brick, soapstone, adobe, fieldstone, river stone are just some examples. If you want to, your design can also include heated benches.

How about the cost? The initial cost of a masonry heater is more than, say, an oil furnace, but then costs less for fuel. Our brick-faced, relatively simple, masonry heater cost about $13,500, including its foundation, the heater core, facing material, and a two-flue chimney I asked them to build. Let’s assume we use four cords of wood per year, which is equivalent to about 700 gallons of heating oil. Since I work up our wood myself, our wood is “free” (Hmm…). If we had purchased wood at $200 per cord, our annual costs would have been $800.

If we had installed a new oil furnace, our initial investment would have been much lower, but our annual fuel costs would have been much higher. A new oil furnace installation would only have cost around $4000, less than a third of the cost of our masonry heater. However, we would have used about 700 gallons of fuel oil each year. Using the average cost of heating fuel from 2001 to 2018 (about $3.00/gallon according to the NH Dept. of Energy), we can do a rough comparison of my actual costs for heating my home using the masonry heater with what it would have cost if I had installed an oil furnace.

So, my actual cost for heating my home with the masonry heater was just the initial cost of the heater: $13,500. If I had actually bought four cords of wood each year at $200/cord, then my cost for fuel over 17 years would have been $13,600 (17 years *4 cords per year * $200 per cord). The total cost would have been about $27,000. If we had instead installed an oil furnace for $4,000, we would have paid another $2,100 annually for fuel oil. Over the course of 17 years, we would have spent roughly $36,000 for 12,000 gallon of fuel oil, and our total cost would have amounted to nearly $40,000. So, a masonry heater can definitely make economic as well as environmental sense. It can even make sense as a retrofit. How much and which type of fuel you use and to what degree you use your masonry heater instead of your current system will influence your payback time.

For more information about masonry heaters, including a gallery of photos, check out the website of the Masonry Heater Association of North America (https://www.mha-net.org).

Dan Crosby, lives in Bethlehem, NH. He is a member of the Ammonoosuc Regional Energy Team, an all-volunteer non-profit organization that encourages and supports economically and environmentally sensible energy practices in the Ammonoosuc region of northern New Hampshire. For more information about ARET and local energy solutions, go to www.ammenergy.org.

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