Masonry Heater Build

[byQ]

I'm building a small house (~1300 sq. ft), and building a masonry heater. I don't know if there is much interest but I thought I would add pictures/info as this happens.

Intro: Masonry heaters are thermal mass units that weigh a lot (2000-10000 lbs). A fire is usually burned once a day (full rapid burn for 2-3 hours). The exhaust/smoke path takes a serpentine route through bricks/rocks. The btu's are absorbed into the rock/brick and slowly heat is let out over 24 hours, or so. Masonry heaters are very popular in Northern Europe (Norway, Sweden, Germany, Russia, and Finland). And they are starting to become more popular in North America, especially Eastern Canada and Washington state. Wood burners in US are just learning about them (and the other mass heater - rocket mass stoves)

I'm building a medium sized contraflow heater from plans purchased from the masonry heater association (mha-net.org). Contraflow means the air flow/exhaust in the heater goes up vertically and then down vertically, then out the flue. In contrast, a Russian heater has the smoke path going horizontally.

Here is the house plan I'm working off (sorry this is my working copy - it got rained on, burn marks from steel cutting, dirty and crumpled). Anyway the red box represents the footing for the masonry heater - 12 inches deep with rebar, 12" o.c.). I've tried to centrally locate the masonry heater, and get it positioned so the flue is close to the highest point of the roof.

The orange boxes are roll-out racks to store firewood - that is the firewood is hidden until needed . I think I should be able to stuff a half cord under the dining table. Also notice the two "hot rooms" for collecting heat in their thermal mass from the sun instead of from a fire. I'll just add pictures/info during this build process.

Oh here are some photos of masonry heaters. Note the three different textures, stucco, natural stone, and brick. Q

 

[rideau]

Sounds like an exciting project. I can't read your plan, even enlarged. I really don't think you can count on storing 1/2 cord under your dining room table, even if it is a face cord you are talking about. That's an area of 4 feet by 4 feet by 16 inches. Is you table even 4 feet wide? Where are peoples' legs going to go? You don't want to spend your life being uncomfortable while you eat. That is a lot of wood to store indoors (bugs). Plus a bit inconvenient both storing the wood under there and getting it out. If you have kids, food gets under the table...and if you have pets they love to lie under tables....Anyway, seriously think about that idea.

 

[Seasoned Oak]

What about surrounding an existing EPA stove with a few ton of masonry. In close proximity, since the distance to NON combustables is essentially about zero. than would be a relatively easy project for a DIYer. I thought of this as my stove produces way too much heat for the 18x18 foot room its in and the room is usually in the 90s when stove is going.

 

[byQ]

Moderator, this doesn't appear to be the right section for masonry heater stuff. Is it possible to start a mass heater forum to include masonry heaters and rocket stoves/rocket mass stoves?

 

[begreen]

This is fine. Fireplaces are included in the hearth section. Keep us posted on your progress. We all are familiar with masonry heaters. I'm eager to see what you create.

 

[Trilifter7]

I love the natural stone look with the black glass doors! Beautiful heater!

 

[Seasoned Oak]

Do these types of wood heaters actually burn the smoke? IF not then they are not as efficient as touted. Id think you would need a way to introduce superheated fresh air into the flue gas stream somehow the way the EPA stoves do.

 

[webby3650]

They do achieve secondary combustion and produce very little, if any smoke. It's a very cool idea, but it comes at a very large expense and loads of time. Someone posted a video a few days ago of a fireplace conversion to masonry heater. It's very cool! But after 5 weeks, 10,000 lbs of stone, a structural engineer, heater designer a heater mason and probably $40,000, it only reduced their oil consumption by 20%! A free standing stove would have taken 1 day, $4,000 and could produce 100% of their heat. It just seems more like a novelty to me, not real practical for people.

There is a very cool on at the Chimney Safety Institute in Plainfield,Indiana. It's very impressive!

 

[Seasoned Oak]

Again, cant the same heat storage be achieved by building a cement or stone structure around a regular EPA stove. Im tempted to try this as my stove sits on a concrete foundation on the basement floor.

 

[webby3650]

I don't think this would be anywhere near the same kinda heat storage here. A masonry heater is made so the flue gases circulate around the firebox, then the super heated flue gases pass through several tunnel passages before going out the flue. Releasing most of it's heat into the stone. We are talking about no less than like 4,000 lbs here, it would be difficult to get that much stone around a stove, and there would be very limited exposure to the kind of heat that would be required to store usable heat.
It very well could soak up a bunch of heat from the stove and then release it to slowly to do much good at all, especially in a basement.

 

[Foragefarmer]

I have been reading ASTM E1602 in order to gain a firm understanding of the applicable codes and engineering involved in a masonry heater given that I have a good location for a medium sized one as well. I also look forward to your build.

 

[Nick Mystic]

Our Jotul F600 sits on our hearth extension in front of an open fireplace with a block off plate installed. The F600 has about a six inch section on the rear of the stove that sticks inside the fireplace. The fireplace and chimney have over 6000 bricks in them that clad the cinder block structure inside that houses three tile flues. The entire structure spans three stories when you include the lower level of the house and the cathedral ceiling and loft area. As such, is provides a rather massive thermal mass for trapping and slowly releasing heat back into the house when I'm burning. I only installed the Jotul this past February, so I don't yet have good data, but the temperatures I recorded with my IR thermometer were impressive.

While this set up is not designed to work as a masonry heater, I think it works something like Seasoned Oak was considering. I'm looking forward to next burning season to get some better data on the heat generation I get off the structure. Here are a few photos:



The fireplace and chimney are eight feet wide and four feet thick. On the backside of this structure is our kitchen. After having a fire burning for a few hours I took some IR readings from the kitchen side of the structure and was surprised to see it was about 90 degrees while the house was about 72 degrees and it was about 30 degrees outside.

 

[DevilsBrew]

Hey Q. I'm a masonry cheerleader. Please post pictures of your build. When are you starting?

 

[DevilsBrew]

If anyone is interested, there are plenty of masonry heater threads on this site.

 

[byQ]

Hey Q. I'm a masonry cheerleader. Please post pictures of your build. When are you starting?


Thanks DB. Here is where I'm at now, working on slabs for 2 rooms that are south facing so they will be used to collect free btu's from the sun (black insulated thermal mass & lots of windows). I'm going to build cinder block walls in these 2 hot rooms (see pallets of cinder blocks). I will start digging out the 8' x 8' x 1' hole for the masonry heater in a few days, so I guess I'm starting the masonry heater build. Also, I got the masonry heater door back from the welder - the cast iron was cracked (see pictures). He welded it from the inside - looks good (only $170 total for this $700 door).

 

[begreen]

How will the walls be insulated?

 

[byQ]

How will the walls be insulated?


The slab floors in these "hot rooms" will be 3" rigid board (r-15) but the cinder block walls are uninsulated. These walls are inside the house - like a greenhouse. They collect heat from the sun and then slowly pass it into the main house. There will be roof overhand to block the summer sun but the lower angled winter sun will blast right into these rooms. I read some studies and it was found that black really absorbed radiant energy - about twice as effectively as most other colors. So they will be black.

Oh, do you mean the walls of the house? They will be of ICF (insulated concrete forms) construction.

 

[Michael Golden]

Is this gonna be a half buried house? Saw in the plans sky tubes. Looking forward to the build!

 

[Hogwildz]

Well ya won't have to walk far to take that morning piss.

 

[webby3650]

The fireplace and chimney are eight feet wide and four feet thick. On the backside of this structure is our kitchen. After having a fire burning for a few hours I took some IR readings from the kitchen side of the structure and was surprised to see it was about 90 degrees while the house was about 72 degrees and it was about 30 degrees outside.

Just think how much heat is being pumped up and out through all that brick to the outside!

 

[DevilsBrew]

What type of masonry are you using for the stove/heater?

 

[byQ]

What type of masonry are you using for the stove/heater?


There are several options for facing,
* common black stone, dense, ideal thickness of 3-4"


Bricks - 3 options,


And natural flagstone, used as a facing (1/2"-2" thick),



And here is the super duty fire bricks - notice how large they are compared to a common brick. They are dense weighing 10-12 lbs each. The four lower rows (about 70%) are #1 arch which means 3" on one long end and 2.75" on the other long end. The other 30% are straights. I figure I can use some of the arched ones but they must be positioned in such a way as to cancel out the arch/angle or put in places where the arch doesn't matter. The masonry heater's firebox is double walled so the arched bricks will go there and the angles will cancel each other out.

 

[byQ]

Fire bricks,


I'm leaning towards a natural stone facing. The gray field stone probably. And maybe use the bright green stone as accent. The cut square/rectangular gray/greens would look nice, though.

 

[Mackj]

Very cool! I have a friend with a similar set up and am very impressed. I hunt his property and will often visit after a morning hunt. It is always toast and usually it is residual heat from a fire the previous evening! I did not understand what he had there when I built my house. My insert is cool but his set up is great,I have been considering what it would take to do this at my place. It would be a big project! Wish I would have considered it when we built. Looking forward to seeing your project unfold!

 

[DexterDay]

Here is my subscription to the thread. I find this very interesting.

I wish you the best of luck and look forward to the finished product and your review after the1st yr.