Comments on my
Summer Project List Progress
post expressed an interest in our masonry heat stove project. In the US
(Canada too?) we are probably more familiar with either fireplaces or what we
call a wood stove, which is a cast iron box with a chimney sticking out the
top. Masonry type heaters, on the other hand, is more popular in other parts
of the world.
The technology for this method of heating is quite ancient. Wikipedia reckons
there were forerunners of it as early as 5000 BC. The gist of the masonry
stove is that they are designed to retain heat for as long as possible. This
is basically accomplished by two things. One is an indirect pathway for the
heat and smoke. The second is a thermal mass, which is basically something to
retain the heat so that it radiates slowly to the house. Commonly, it's an
empty box. Something like this . . .
Because it retains and radiates heat so well, a masonry heater typically only
needs a fire twice a day. You can see how this would save on wood. There are
many styles to accomplish this, and following are some examples.
This one is a typical Eurpoean Kachelofen (tiled stove). Usually these are quite huge and ornate.
Here's a modern version, without tiles.
In ancient China, the masonry heater was called a Kang, with the thermal
mass fashioned like a large platform. This artist's sketch was made in 1851.
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Unknown author, Public domain, via Wikimedia Commons
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It was used for heat, cooking, sitting, and comfortable sleeping, like this modern version in a Chinese hostel.
A modern adaptation of the masonry principles is the Rocket Mass Heater, where the thermal mass becomes
an area for seating.
The innards of the RMH are a bit different, although the principles of heat
retention and thermal mass are the same.
As you can see, a different path for the smoke and heat, but it accomplishes
the same heat retention. An improvement on this design is the firebox/riser, with
it's swirly smoke path. This burns the wood gases like a catalytic combustor,
which in turn creates more heat and cleaner smoke.
One more example, of a modern masonry stove that combines features.
It combines thermal mass with a bench/single bed, plus an oven! Some of them
include cooktops.
The design Dan is using is one of the many recent adaptations of the masonry
stove principles. More on that soon.
17 comments:
The part that most intrigues me is how do you get it to draft properly starting out? With such a long and winding path for the exit of flue heat and gases, I imagine it would need some sort of boost so you didn't fill your house with smoke.
Ed, good question, because draft is key. I can't answer it from experience, but I am reading that it requires a different fire-starting technique than a fireplace or conventional woodstove. I'm guessing we'll have a learning curve, but it doesn't seem to be a problem in general.
I have the same question as Ed. But wouldn't it be loverly to design a house around stoves like this, with beds warmed with them and food cooked by them???
Michelle, lots of people do just that! They decide on the stove when they make plans for their house. We're stuck with retrofitting, but I think it will work out.
I recently discovered that I need to have my chimney either repaired or rebuilt - the only difference is the price of the brick, so I guess I'll go for a rebuild. It made me think about whether I should just stop burning wood which is such a lot of physical labor and now I can't even split it myself which is one task I miss very much. But I'm taking down a couple of huge trees, so it sure doesn't seem like a time to stop burning wood.
Quinn, I hate that. But it's good you have it inspected; better be safe than sorry. Maybe a chimney liner would be a possibility. I don't know that much about it. But I do know I love having wood heat, even if it was just a back-up. Plus it's a good thing to do with those downed trees.
The masonry stove uses less wood and smaller pieces. That will be helpful to us.
Thanks for the background Leigh. I have read of them through the Wheaton Labs website but not seen a lot of examples.
TB, the stoves at Wheaton Labs are all the rocket mass heater type. That link is a collection of photos folks have uploaded. Ours won't be like those, but will have the same principles.
A poor man's masonry heater:
https://www.notechmagazine.com/2014/03/crimean-ovens.html
I put one in a friend's hoop greenhouse. Works well. Can burn nasty green pine storm branches in it.
An earth or laid stone floored "Guest house" could be so done.
An engineering note for the Crimean oven is ensure there is a steady uphill from where the burn pit (or stove as we use it for boiling maple syrup) to the other end of the structure where the chimney is. Helps with draft and any groundwater drainage.
A more "Civilized version" https://www.notechmagazine.com/2017/02/medieval-heating-system-lives-on-in-spain.html
Michael, thank you for the links! It's amazing how sophisticated "primitive" technology can be. The Gloria looks like the original j-tube heater.
You probably has seen zillions of You Tube video's about building one. I quite liked the one of a Dutch man restoring a old Cabin in Italy. He build a masonry stove as well with a oven above. Might be interesting: https://www.youtube.com/watch?v=zegG9a7xq9M&list=PL32DhVYS_cmHiaXrLb7Ovr14g88NIpxJ0&index=4. His name is Martijn Doolaard
Wendy, thank you! I will pass the link on to Dan. He has watched a ton of masonry stove videos and gotten a lot of excellent ideas. Europeans really have the technology and skill down. We're also amazed at the kinds of masonry resources they have. We're so limited here in the US.
Beautiful, and interesting, Leigh. One question: How does one clean the flue? and is there more of a build up as the exhaust has to travel a longer, more circuitous route?
Rosalea, a little cleanout door is added where needed. With the batch box style firebox, there is actually less buildup of ash and soot because it burns more efficiently. The wood gases are burned in the firebox (instead of exiting out the chimney), getting more heat out of the wood and less residue in the smoke.
The Masonry Heater Association (mha-net.org) has a plethora of information on masonry heaters
Scott, thank you for that! I'm not sure if Dan has explored that site, but I'll pass the link on.
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