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Several years ago while working for another Ottawa masonry contractor, I was invited into a local mason’s home where he showed me his homemade Masonry Heater. It was an enormous unit faced with clay bricks and Indiana limestone copings. He claimed the heater would heat his home all winter by radiating heat similar to hot stones in a sauna (minus the steam of course). Gushing over how incredible it looked, I had to get home and learn more about it. A couple years later we had to do some stone repair on a client's custom built soapstone heater’s chimney and had a similar experience of awe and curiosity over such a unique way of heating your home. Having been bitten by the “homesteading bug” it’s a fantastic method of heating your home in a more self-sufficient way, with a renewable resource and does not require any electricity.
The problem I discovered when researching, was how little information there was out there on these heaters aside from the Masonry Heater Association website and a few obscure online chat forums. While historically, they have been a popular heating choice in Scandanavian countries, the designs and knowledge of them have not made its way into the mainstream here in Canada. Eventually I had gathered enough information to feel confident in the cost benefits of constructing one and chose to build one in our 120+ year old log home.
The purpose of this post is to provide more information about our own experience having gone through the construction and now through our first winter with a Masonry heater as the primary source of heat for our home. I am by no means an expert on Masonry Heaters which is why this is a case study.
Thermal Mass Radiant Heat vs. Standard Wood Burning Appliances
The main problem heating with wood in a normal fireplace or wood stove is that the majority of the heat produced goes out up the chimney leaving only the area directly in front of the fireplace benefiting from the heat which is very inefficient. They require the constant addition of more wood and can make the room they are in uncomfortably hot while the rest of the house is much colder.
A masonry heater is a large thermal mass of firebrick, cast refractory, and typically brick or stone as the facing. They are constructed so that the hot air from the firebox has to travel through a series of channels and cavities before making its final exit out the chimney. Since this hot air has to travel much farther before exhausting out of the chimney, much more of the high temperature heat is captured. That heat is then transferred to the out facing brick where it slowly radiates that heat throughout the day after a hot 2.5 hour burn.
Some masonry heater core manufactures boast their units have up to 90% efficiency ratings, whereas a wood burning fireplace typically runs at a mere 10-30% efficiency which is a huge difference.
Our Heater's Design
The one designed and constructed at Kavanagh Masonry HQ was built with the overall square footage and footprint of the home in mind. Our log home is roughly 1,100sq ft. and so our heater requires a much smaller fuel load and firebox to heat the home. The firebox is only 13 inches wide and 18 inches deep which is very small for a firefox using standard cord size wood.
Most heater cores are built for a modern home with 8’ ceilings but because our old home has a much lower ceiling height, in order to meet building code requirements for clearances to combustibles, the manufacturer designed the core with one less chamber above the firebox to lower the overall height. In order to facilitate height issues further we opted to side vent the chimney on the side of the heater.
The chimney runs upstairs directly through the bedroom which makes sleeping in the winter pleasantly warm and comfortable. The ash cleanouts were built into the heater foundation in the basement to make cleaning more efficient and less risk of a mess on the main floor.
We chose to face the heater with clay bricks because it can handle thermal stress much better than most stones and suited the history and aesthetic of the home nicely.
All these design choices would categorize our heater as considered a “light unit.” Heavier units would typically hold heat longer and are less responsive.
Important Data for this particular Heater
-Requires 2 fires a day spaced roughly 12 hours apart.
-Fuel load per burn is approximately 35 lbs. which works out to 6 pieces of standard split cord wood per burn.
-Wood is stacked all at once in a log cabin style burn using one year dried hardwood with typically cedar kindling and two pieces of newspaper placed on top to start the burn and help initiate the updraft.
-One burn typically takes between 2-3 hours from start to finish.
-Once on a regular firing schedule, the heater will heat the house for roughly 16 hours radiating its heat throughout our open concept home.
-On days where outdoor temperatures are above 0 Celcius, only one fire a day is needed.
-Our home through winter ranges from 66-74 Fahrenheit using the heater depending on how cold outside it is.
-The heat feels much warmer than what comes from a forced air gas or propane furnace because the comfort temperature zone of radiant heat is much wider. Radiant heat helps to warm the surface temperatures of all objects in the home much more than forced air systems. This means that a temperature of 66F from a radiant heater feels more like 68F from a forced air furnace.
Cost Analysis
I received a contractor discount at my suppliers for the majority of the materials used in this project and because the core for my heater was so small, it was the cheapest available option from the manufacturer. From pouring a new foundation to putting a rain cap on the new chimney pipe, I estimate I spent roughly $25k (CAD) for all the materials, dump fees for old slab, inspection, and delivery fees. A more standard sized heater at retail pricing I would estimate a cost of $33-45k just for materials.
Though we have not run a full winter with the heater, if we compare the cost of heating with propane, and no price changes in cost of propane or cost of cord wood, I am projecting the heater will pay for itself in roughly 11 years as wood is much cheaper to source than propane here in Ottawa.
Cons
-Supervision: In order to capture the most heat, the fire does require some attendance. Once to rake the embers closer to the air inlet to burn faster and once to close the chimney damper once the fire is done. This means that you do in fact need to be there roughly 2.5-3 hours after the fire starts to close the damper and air inlet. Not an issue if you’re an early riser or work from home, but it is a con.
-Less responsive: In order to heat effectively, you really should be firing it twice a day in peak winter and once a day in the shoulder seasons. If you have to leave home for a couple days, it can take almost a full 24 hours and 2 fires for it to really start heating your home again because you are starting from cold bricks again. This is why you should always have a secondary source of heat as a backup for when you are away for extended periods of time.
-Detail & Cost: Without proper care and attention to detail when constructing, it would be very easy to make a leaky heater or a heater that has problems especially where metals components are needed. If you were to construct one, you should to hire a reputable masonry contractor or a heater mason to really make sure it is built correctly and last decades without any repairs. The cost itself is quite high but in my opinion nothing beats heating with wood and you never have to worry about heat during a power outage. While you could build a cheaper core out of firebrick yourself following online plans, you’d never be able to get an inspector willing to sign off on it as there is no one to pass the liability on to. You have to buy the core from a manufacturer and build it in accordance with their blueprints.
-Drier Air: Winters in Ottawa always create a drier home environment but the heater did noticeably contribute to the dryness of the air. The problem was remedied with a small $100 humidifier.
-Cracking: Difference in expansion rates and thermal stresses make hairline cracking inevitable on a Masonry Heater that is in routine use especially on stone faced heaters. While they are hardly noticeable, it can occur and may be an aesthetic problem for some.
Overall
Nothing beats the site of a roaring fire and the feeling it produces. We love our Masonry Heater and the beauty it provides to our home. I would highly recommend anyone interested in heating with wood that have the budget for it to consider a Masonry Heater for your home.
If you are interested in getting a masonry heater put in your home or other masonry related services in Ottawa such as chimney repair, fireplace brick repair, fireplace facing brick and stone, feel free to reach out on the Request a Quote page or call 613-859-5090 to discuss the scope of work. All work at Kavanagh Masonry is done by a Red Seal licensed mason.
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