Tulikivi / Masonry heaters - 101
So perhaps you're a little unclear on what exactly a masonry thermal mass fireplace is or how it works. Fret not and read on, in 5 minutes you'll understand the concept and operation of thermal mass masonry heaters. Check out the FAQ and resource pages for more information on project planning for a Tulikivi soapstone fireplace. Get a sampling of Tulikivi styles in the photo gallery and contact us for a free catalog with the complete line. Your opinion is important to us, so feel free to send an email with comments or suggestions on things you like about the site, or how we can make improvements to provide you the best information possible.
Topic 1: Thermal mass.
(with excerpt from Wikipedia)
As a complete technical description of thermal mass is unnecessary for our purposes and beyond the scope of this document, we will simply proceed with a generalized understanding that "thermal mass is the capacity of a body to store heat".
"Thermal mass as a concept is most frequently applied in the field of building design. In this context, thermal mass provides 'inertia' against temperature fluctuations. For example, for a building, when outside temperatures are fluctuating throughout the day, a large thermal mass within the insulated portion of the house can serve to 'flatten out' the daily temperature fluctuations, since the thermal mass will absorb heat when the surroundings are hotter than the mass, and give heat back when the surroundings are cooler."
Topic 2: Stone
So all I have to do is take, say, 5,000 pounds of stone, warm it up with some fire, and voila, I've got my very own thermal mass? Well, it's really almost that simple.
In most fireplaces and stoves usable heat energy is wasted after combustion by shooting hot flue gases straight up and out of the chimney. Capturing otherwise wasted heat in the first place is good, but the ability to store it over an extended period is what makes soapstone an ideal building material for Tulikivis functionally as well as aesthetically. The "contra flow" channeling inside a Tulikivi masonry heater maximizes transfer of heat energy as the hot flue gases are directed throughout the stove on an indirect path to the chimney. As you will see, when actually try to heat up 5,000-10,000 pounds of rock with a fire, the contra flow channeling concept employed within your Tulikivi could prove a great benefit to you.
While the exact path taken through any particular heater depends on various factors, the basic flow path is generally configured in one of two ways, depending mostly on where the best place is to connect with a chimney system.
In the case of a "base vent" heater (shown at right)
Topic 3: Fire.
"Fire good", as whomever discovered we can harness its power might have said. In the case of masonry heaters, fire is good. Rather than building several fires a day and banking hot coals to retain some heat between them, you burn your masonry stove wide open until only ashes remain. In Tulikivis the amount of wood consumed is usually 1% of the stoves gross weight, so, in this case, our 5,000 pounds of soapstone would take about 50 pounds of wood (2-3 armloads) in a 2-3 hour fire to saturate it with heat for around the next 12-24 hours.
The most important thing to remember about masonry heaters is that hot fast fires are the key to maximum performance. Very high combustion temperatures are desired and they can reach up to 1800° F in the heater's core. Sounds pretty toasty in there, but this means no creosote buildup in the stove or chimney, and at 1-2g per hour, very low stack emissions of particulate matter left over from incomplete combustion.
The Synopsis: Wood heating with Tulikivi is win win.
That's thermal mass heating at work for you; hot fast fires that store heat in stone make wood fired masonry heaters a low polluting efficient use of natural resources. The best part about Tulikivi soapstone masonry heaters is that while you're making efficient use of resources you get not only the enjoyable choreography provided by dancing flames, but also a gentle warmth that slowly radiates from the heater 12-24 hours after the fire is gone.