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Seeking advice, wondering if there is any advantage to building a concrete (cinder blocks filled) mantle around my wood stove?

It would look something like below

_____   _____
| ___| |___ |
| |       | |
| |       | |
| |       | |
|_|       |_|

The house is a split that's about 2300 sq/ft and the stove is in the basement

Would this add any value, if not is there anything that's DIY and not ugly? (I have others in the house to consider)

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  • Thanks for the reply, the rocket stove looks really appealing from the little I have read. Also from the little I have read I see the are issues with commercial availability, insuring and permitting. I'm from nova Scotia, Canada and can't seem to find anything that suggests and type of certification. Thanks again – dblburner Jan 5 '15 at 16:14
  • Why do you want more thermal mass? Do you use your basement (where the stove is) for anything? How does the heat from the oven get to where you want it warm now? – mart Feb 12 '15 at 16:44
  • In most jurisdictions a masonry stove, russian stove, rocket stove is considered a fireplace, and there are no applicable fire codes. Go figure. – Sherwood Botsford Feb 12 '15 at 20:39
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Yes, but not that way. You need far more mass than that. You need 2-5 tons of brick around the stove. This will require extra support underneath. 6x6 beams under the affected part of the stove with teleposts should be sufficient.

Google "Russian Stove"; "Masonry stove" or kachelofen.

http://heatkit.com/docs/course.PDF describes using a steel insert into a kachelofen

Another option is a 'rocket stove'. These are made of clay instead of brick, and generally are easier for an amateur to build.

Mart has a good point about basement, although, not quite the right reasons.

I've heard of cases where people have put a wood stove in the basement, expecting the heat to rise thorugh the house. This sort of works, but often results in the basement being way too warm, and the top floor way too cold.

The house my mom grew up in was heated with a wood stove on the main floor, and grated holes in the floor to allow the heat to circulate. (She describes standing over a grate in her night dress getting everything toasty before getting into bed.) But the wash basin on the night stand would freeze some nights.

A thermal mass stove functions in multiple ways: 1. As a radiator. This will not be like the radiators used in lobbies between the inner and outer doors in stores, or like the glowing dull red electric heater, but far more like the oil filled steam-radiator shaped electric heaters, but more so.

These stoves typically have an outer surface between 80 and 100 degrees F -- cool enough that you can put your hand on the outside. Yes there is some radiation, but it's on the order of a hundred watts per square meter.

A conventional iron stove is a much better radiator.

Most of the heat will leave the stove by convection. Air in contact with the stove, warms and rises. This works well for a single well insulated room. It does not work well generally for a house. although an uninsulated partition wall will drop the temp by about half the difference between room and outside. E.g. A bedroom with the door closed when it's 0 outside, and 70 inside will reach equilibrium in the 30's. (the exact temp will depend on proportions of exterior wall, window size, insulation....)

Open designs work well, especially if the thermal mass stove is roughly in the middle of the space.

A ceiling fan moves the heat around faster, and reduces puddles of cold air at the base of windows. Left on low all the time they are frugal with power -- 8-15 watts.)

If you want a more evenly distributed form of heat, apply the rocket stove concept, but use it to heat a large mass of water instead of a pile of masonry. Hot water can be kept in an insulated tank until needed, then used the same way hydronic systems are. This has the advantage that it also can heat your domestic hot water, and during part of the year, the heating can be done with solar thermal collectors.

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  • what good is a kachelofen in the basement? – mart Feb 11 '15 at 15:12
  • I didn't suggest putting it in the basement. I suggested beefing up the support underneath it. You could put it in the basement. Heat rises. Put a few grates in the floor and the entire basement ceiling space becomes a plenum. – Sherwood Botsford Feb 11 '15 at 23:08
  • the whole point of a kachelofen is to have radiative, not convective heat transfer. But maybe we schoiul aks the OP what he wants to achieve. – mart Feb 12 '15 at 16:43
  • Where did you get the idea I was suggesting putting it in the basement? – Sherwood Botsford Feb 12 '15 at 20:35
  • And you are not correct that the whole point is radiative heat. The exterior surface of a large masonry stove is cool enough sit or sleep on. Not a very good radiator. The point is to have a short very intense non oxygen starved fire and use that to heat up a very large mass by a small amount. The mass and thickness of the stove means that the surface remains warm for hours. – Sherwood Botsford Feb 12 '15 at 20:38
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No, in all likelyhood not.

What you achieve with adding thermal mass: Wood stoves are cleanest and most efficient when they burn 'at full throttle.' Thermal mass allows you to have short intervals of high heat in the oven, that you store and give to the room in a smooth way. For this to really work, you need a lot of mass - see Sherwoods anser. But you only profit from your stored heat when the thermal mass is where you are. Unless you live in the basement, addin mass to your stove there won't help.
Without knowing more about your house and your goals, it's impossible to say what you could or should do with the stove in your basement.

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  • Thanks Mart and Sherwood. I think the rocket would be the way to go...I only I was better at debating, my partner gave me the no go. – dblburner Feb 15 '15 at 22:18
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To store the energy from a fireplace you need mass.
Solids like concrete can store 0.88 kJ/kgK, Water can store 4.18 kJ/kgK.
So water can store 4.75 times more energy than concrete. Therefore a modern waterbased heating system combined with a waterbased stove can store much more energy and deliver it to any places further away in your house /apartment. Modern stoves have also very low emissions. Another advantage: the mass of concrete you need may overload the ceiling - the water is already in your house.

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