Masonry Heater Question(s)???

[BobUrban]

regarding a masonry heat source as mentioned in many threads(specifically the Cast, steel, soapstone thread)

1. are these specifically designed and build with a stone or brick fire box with just a steel/steel and glass door?

2. or are they a steel box similar to many stoves available built in and surrounded by brick stone and mortar?

3. Could a modern steel square box stove be converted or used for such a heater by surrounding it with brick/stone/morter?

No plans to begin building one but the ideas abound??? Seems like using a modern stove and surounding it with reclaimed pavers like I used to build my hearth would work but I am not trying to reinvent the wheel or burn my house down - just thinking and looking for input?

Is there special bricks or mortar used? Looking at pics on the interweb they look as if they are built with stone and bricks available but, again, I am not in the know. As a welder with access to unlimited pavers I am thinking an outside oven may be a future project. Fresh bread anyone??

 

[Highbeam]

The magic of the masonry heater doesn't seem to be so much in the firebox but in the exhaust pipe routing. Lots of back and forths to extract all the heat. The ones I have seen were all masonry.

 

[agartner]

I don't think there is any rocket science to the materials used - it's more the design of the actual stove itself and how the exhaust is routed throughout the masonry mass to capture all those BTU's that would ordinarily go up the pipe with a more traditional wood stove. The one masonry heater I did see was up at the WoodStock Soapstone in Lebanon NH (I'm close by) - and it was all masonry.

If I found myself with an unlimited supply free of pavers and masonry materials, I'd be thinking "outdoor pizza oven"... but thats' just me...

 

[Slow1]

Based on my reading there are many designs but the common principle of them is as stated here - the exhaust path is routed through the stonework to recapture the heat of combustion. By allowing you to burn hot with lots of air you (in theory) burn a very clean fire - thus the efficiency side. Then the exhaust is routed through the stonework effectively cooling it and heating the stone which then radiates the heat over hours once the fire is out (typically you close off all air at that point).

That said - I really don't think that it would be such a great idea to build around an existing stove. If nothing else I don't think you would gain any benefit and it would make for an expensive firebox in a design that really doesn't require it.

Now - building a nice hearth of stone and such is not a bad idea and you can benefit from the thermal mass of that. A radiant stove would heat the stones and they in turn would serve to help moderate temperatures in the room to some degree. Clearly not exactly the same thing, but...

Being an external wall you are building against (assuming you keep that corner location) if you were to do this then assuming you didn't have to build this for shielding then you may wish to add additional insulation between the wall and the stonework to make sure you keep the heat in the room vs radiating it out the exterior wall. All part of the design if done well...

 

[argus66]

there is old thread on this, all questions answerd.

 

[weatherguy]

 

[Grisu]

Here is a site with a sketch of a masonry heater.
http://www.pyromasse.ca/infoe.html
To my knowledge there is no steel in the firebox. It relies on very hot, but relatively short fires that heat up the masonry which then radiates the heat throughout the day.