Axiom Home Page Forums General Discussion The Water Cooler Masonry Heater is up and running

Nothing to do with audio, but I am slowly getting the bits and pieces up and running at the new house. I fired up the masonry heater over the weekend and am *very* happy with it.

The masonry heater is basically a big wood-burning firebox coupled to about four tons of brick and stone for heat storage. Rather than keeping a small fire going all the time, you burn one big honkin' fire a day and use the thermal mass to absorb the heat and gently radiate it out over a long period of time.

When we were designing the new house, I drew a rectangle labelled "Temp-Cast 2000 Wood-burning Masonry Heater" near the center of the blank page and we built the house around the heater. The living areas all have line of sight to the heater for radiant heating, the bedrooms will be colder but I prefer that for sleeping, and the bathrooms have auxiliary electric heat cables in the floors to keep them toasty in the winter. All in all I'm pretty happy with the house design -- guess it was worth a year of worry and nail-biting after all.

My last wood-burner was a Regency advanced combustion insert, which I thought was pretty darned neat -- a slow, smouldering fire with a boiling blue flame hovering over the wood from the secondary burn. The new heater is much simpler -- the design dates from the 1600's -- but works just as well. There is a secondary air feed for clean burning, but basically you just build a big fire in a well insulated firebox and it gets really hot inside so "everything burn nice".

I haven't heard back from the manufacturer yet re: whether I need to start with curing fires to dry out the mortar -- the heater was built over a year ago -- so I am running wussy little fires just to be safe. Even so, I can run a small fire that looks laugably small in the firebox and still have the thing radiating noticeable heat two days later. Very cool.

After a month of searching I *still* can't find the charger for my digital camera so I can't post a new pic with a fire burning, but here's an old pic and you can imagine the fire, right ?

I've said it before, and I'll say it again: I do believe that you've built my dream home!

How does the smoke get up that chimney?

Thanks, Mark. I was really having my doubts for a while ("spent all this money to build a one room cabin").

The simple answer re: smoke and chimney is "through a pipe". The heater is a contraflow (aka fountain, or Finnish heater) design, where the flames and smoke go up the center through the oven then down channels in each side, warming the entire mass. The smoke channels come together in a manifold which runs under the door in the first picture, so the chimney can be at either side or at the back if you don't have a second door for see-through. The chimney uses an 8" ID round flue, and the same flue pipe is extended to poke into the side of the heater. The result is a toasty-warm bench area over the horizontal flue.



That's the easy part. What had me more worried was "what makes the smoke go through the horizontal flue when you are starting the thing up ?". I figured it would be easy to light once the masonry was warm from a previous fire but a pain getting started -- I had visions of holding a flaming torch through the clean-out door at the base of the chimney to get a draft going.

In actual fact it was much easier. The trick is that the chimney is inside the house, so both the chimney and the heater core are "warmer than the outside" even before a fire is lit. I stacked up a few small pieces of wood in the firebox, put some newspaper and kindling on top, lit the newspaper and "presto" a good strong draft right from the start.

There is an electrically operated damper with a wall switch that provides air through a duct in the basement -- the air then runs through both door frames for preheating and air wash over the glass. If you look closely on the left side of the chimney you can see a pull chain which opens and closes a rooftop damper on top of the chimney. You basically open both dampers, light a fire, then when the fire has burned out you close both dampers to keep the warmth inside the heater and chimney.

I think it is really cool, but then I *am* easily amused

That is one mighty fine pad you got there big John.

I really hate it when guys are smarter than me. That's a really cool way of heating a house (there's something mutually exclusive in that sentence, isn't there? ). I have to agree with Mark. I think you built my dream house. You dirty.........

It's got to be some kind of trick.

I can't take any credit for this, other than convincing builder and real estate agent that this "newfangled" technology would not be a disaster and would not destroy my resale value.

As far as anyone knows, masonry heaters were developed in various places around Europe to deal with rampant firewood shortages during the "mini ice age" in the late 1600s, and the technology hasn't really changed much since then. The big advances are related to making them modular for easier assembly and using ceramic glass in the doors to let you see the fire.

If you don't believe me, I was talking about the new house with a nice old Austrian couple down the road from my old house. I described the heater and they both turned, smiled, and said "he has a kachelofen !!". Both of their grandparents homes were heated with kachelofen (tile covered masonry heaters) in Austria, almost 150 years ago.

http://www.ceramicstoday.com/articles/kachelofen.htm

The most bizarre thing is that masonry heaters are starting to be used with electrical heating elements in the smoke channels. Many countries charge much less for electricity consumed during off-peak periods, so people are using a masonry heater to let them heat up the stove with cheap off-peak electricity then enjoy the heat during the day when electricity is expensive. Apparently Tulikivi in Finland sells almost 50% of their masonry heaters with electrical heating elements these days -- talk about dual-fuel !!

I was able to coax one picture out of the camera before the battery died again. I'm really going to have to find that charger...

Beautiful place you have. Ok, so the brick and mortar mass stores the heat for up to two days. Does that mean you really only need to fire up the stove with one good fire per day to get/keep the house warm? I think you are on to something there. Efficient way to warm the house, and who doesn't like having a fire going for pure aesthetic reasons.

By the way, what is the temperature during the day in your neck of the woods this time of the year. It won't be long and you will really see the benefit of having a heating system like that in place.

Hey John!
I have a question also:

If you DO want a fire for aesthetic reasons, is there a way to "bypass" transferring so much of the heat to the masonry via a fan or different duct? Or, would you have to walk around in your boxers for three days because the place is too hot?

>>Ok, so the brick and mortar mass stores the heat for up to two days. Does that mean you really only need to fire up the stove with one good fire per day to get/keep the house warm?

Yep, that is one of the biggest attractions of masonry heaters, especially the fact that you don't need to get up in the middle of the night to feed the fire. Your "one fire a day" obviously has to be fairly big, maybe 50 pounds of wood, but you still end up burning less wood than a typical woodstove would consume given the same heating task.

When it's bitterly cold I expect it may take two fires a day, one in the morning and one in the evening, although the house is pretty well insulated so one might be enough.

>>If you DO want a fire for aesthetic reasons, is there a way to "bypass" transferring so much of the heat to the masonry via a fan or different duct?

The custom-built heaters often include dampers to bypass the masonry mass, or to let you run a small fire in a cooking oven/stove without firing the heater, but this one uses a prefabricated modular heater core and is pretty basic, so no bypass. We thought about it, but since I have the chimney pretty far away from the heater core there was no obvious way to put in a bypass.

The really fancy custom-built heaters have benches (heated with smoke channels) poking off into other rooms, coils of pipe for hot water, ovens and smokers built in so controlling all the dampers is a bit like operating an old steam engine.

>>Or, would you have to walk around in your boxers for three days because the place is too hot?

Of course not, I have air conditioning

Seriously, masonry heaters require a bit of planning ahead, and if the weather suddenly turns warm after you fire the heater you might need to open a window or something. The nice thing is that since so much of the heat is radiant (ie the air temperature might be lower than normal but you still feel toasty warm) this isn't as much of a problem as you might expect.

I wanted to build at least one conventional fireplace into the house so I could keep a small fire going for aesthetics, but the house was already way past my original budget and there was just no way I could add anything else.

My original plan was to start with just a big daylight basement, subfloor and tarps over the subfloor, finish one corner with a small gas heater and a big-ass woodstove, and live in there until I had more money saved up and knew what I wanted the rest of the house to look like. Unfortunately existing zoning laws prevented me from living in a partially-built house (that used to be a fine old tradition in Toronto) and newly passed laws meant I needed to build *now* or lose the ability to get a building permit.

>>By the way, what is the temperature during the day in your neck of the woods this time of the year. It won't be long and you will really see the benefit of having a heating system like that in place.

This September has been warmer than normal, typically 70 during the day and 50-60 at night. Right now I am just running baby fires to make sure the mortar is dry.

I also need to buy firewood, which seems crazy since the house is in the middle of a forest, but the heater needs seasoned firewood because of all the twisty smoke channels. Apparently the norm for these heaters is to have the chimney inspected every year and cleaned perhaps every 10 years -- the firebox gets very hot so the fire burns cleanly.

Sounds like your weather, at least for now, is similar to ours seen typically in Missouri at present time. You mentioned that you need to buy cured wood. I guess cleaning the creosote from the flue channels could present some challenges, especially if it were an elaborate configuration with all the options.

Fantastic home - and I love the heating system!!! From what I've read, your only other source for heat is the electric infloor heating in the bathrooms, is this correct? Do you have a back-up heat source in the house? From some of your other posts, I gather you live in a fairly isolated area outside Toronto. What is your plan when/if you leave the house for extended periods during the winter? I assume you have a friendly neighbour who could light a fire in your house every few days if you spend a week or 2 in sunny Mexico during the winter? Actually, I'm in Sudbury, and a week or 2 near Toronto in that beautiful house would be like a holiday for me... and I know how to light a fire... I might be onto something

Thanks !!

When the house was being designed I organized an impromtu "design committee" including, among other people, a family friend who was also my real-estate agent.

"The committee decided" that the house would also have a conventional furnace. I went with propane for convenience -- it's more expensive per BTU than oil but the masonry heater will carry much of the heating load. Also, it seems that insurance companies strongly prefer wood heat to be secondary, not primary.

If I go away for more than a few days I have someone stop by periodically and make sure the furnace is still running. If I ever get time off to take a real vacation I'll give you a call

>>I guess cleaning the creosote from the flue channels could present some challenges, especially if it were an elaborate configuration with all the options

Exactly. Burning it out seems to be the only practical option, and even a masonry heater has a tough time surviving a creosote fire undamaged. When you need to run a heater on uncured wood, the most common solution seems to be the "Russian Heater" approach, where the smoke channels are horizontal and easy to access. Normally Russian Heaters are built entirely from brick, so the mason just leaves one or two unmortared bricks at the end of each channel. When it comes time to clean out the heater, you just pull out the loose bricks and "presto" you have a cleanout. If you want to be fancy you can use cleanout doors

Very cool John. I haven’t seen one of those before. A friend of mine just built a home and put in a beautiful soap stone fireplace from Sweden I believe. Same principle: thermal mass. They had to design the foundation to support its weight.

That sounds like a Tulikivi from Finland ?

That was what I had my eye on initially. They are beautiful, but even more expensive than a built-on-site heater (since everything has to be shipped from Scandinavia) and I have to admit that soapstone wouldn't have fit the style of the house as well as a big stone-covered monolith.

My original sketches for the house had a straight-walled two-story great room with flaming torches around the periphery, a walk-in fireplace and a chandelier about the size of a mid-sized car. It was immediately vetoed by the real-estate agent

I suppose you had to rename the Dungeon, too.

Yes, it is now the Treehouse (loft) and not nearly so interesting. On the other hand I should have a loaned minibar fridge and hotel lobby wheeled bar up there in a week or so (piano didn't quite fit so in goes the bar) so it's not a total loss.

Yep, that sounds like the one I was coveting. Probably cost over $30K installed, not counting foundation. Worth every penny if you can afford it IMO, but it was out of my budget. Mine was about $5K for the heater core kit plus the local mason's time for chimney, stonework, benches etc...

Your friend's heater sounds something like this :



One note for anyone interested in building a heater -- I used a mixture of Arriscraft and local granite to cover the heater. Arriscraft was recommended over cultured stone because it was supposed to transmit heat much better where cultured stone would trap the heat inside. Initial results indicate that Arriscraft is not transmitting much heat either, and it's only the granite mixed in which makes the heater work properly.

Before you ask, the reason for considering cultured stone was that the builder was finding that outside stonework was becoming prohibitively expensive as the local masons retired and were not replaced, but cultured stone required much less fitting and so the costs were both lower and more predictable.

As with the flaming torches in the great room, the outside finish started with "big slabs of limestone", the builder responded with "cultured stone", and we settled on Arriscraft which was also a manufactured stone but without any attempt to look like real stone. Since we wanted to use the same stonework on the heater to tie the inside and outside together, the supposedly better heat transfer of Arriscraft was another argument in its favor.

Fortunately, the mason thought the Arriscraft was "boring" and mixed in some local granite, which really looked sharp and didn't blow the budget. The same approach was used on the heater, and right now I think the mason's decision to mix in granite ended up saving my butt. If we had used nothing but Arriscraft on the heater I think I might be looking at tearing the stone facing off and starting over.

EDIT - Aww crap. Tulikivi's are on sale and the prices seem pretty good :

http://www.warmstone.com/pdf/TU2200%20CAMPAIGN.pdf

John
The fireplace looks wonderful and I love the fact that you only have to stoke it 1 or 2 times a day yet it continues to provide heat long after the fire is out. I also burn wood to help heat the house and love the warmth and ambiance it provides, but I use a conventional airtight fireplace insert. It provides great heat when it's going but I have to continually stoke it every couple hours. If I go out for 3-4 hours, I'm lucky if there are a few coals left to get it going again. Your system will be way less hassle and time to operate. If I ever move I'll have to consider going the route you have.

How many cords of wood do you think you might burn in a fall/winter/spring cycle? I go through about 2 cords (assuming I cut that much or more the preceeding spring while out and about in the woods) but I only burn intermittently for the reasons mentioned above.

Paul

Based on my propane consumption last winter I'm guessing 2-3 cords of hardwood or 4 cords of pine (I live in a red pine forest) if I wanted to heat entirely with wood. This is based on BTU content of propane vs. wood and the best efficiency information I could find on each kind of heater.

The furnace is over 90% efficiency, including both unburned fuel and heat lost out the exhaust vent, while the numbers I could find for the heater indicated 94% burn efficiency (ie 6% of the burnable gases get away) and 65% heat transfer efficiency (35% of the heat goes up the chimney) for a total of about 60%.

I'll let you know for sure in April

This winter might be a bit of a challenge since I need to find a few cords of well seasoned firewood and by September the piles of seasoned wood are getting low. The local firewood vendors are starting to sell green wood and fake a coughing fit when you ask how long ago it was cut.

Another milestone. First baked goods out of the pizza oven. It's more like a sorry, greasy excuse for a foccacia than a pizza but it sure tastes good. Then again, since this is a "black" oven which can only be used after the masonry heater fire has gone out, I might have just been hungry.

Here's the oven door open with the bread ready to remove. I used a pizza pan rather than sweeping the ash off the floor of the oven.



Finished product, cooling on top of the oven. It's your basic beer-based pizza crust, drizzled with olive oil then sprinkled with salt, pepper, crushed chilis, sesame seeds and basil. That's what happened to be sitting on the counter.



Close-up of the finished bread. Obviously a bit too much olive oil.



Currently 48F outside, 68F inside, furnace still turned off. Still running "tiny" fires, basically 2-3 typical pieces of firewood per night, split into ~ 8 sticks each 2" x 3" or so. Parts of the house are a bit cooler but nice and warm around the heater.

I just took a moment to search for some photos of John's house...i.e., my dream house:

OK, what the heck. Here are *all* the pictures. The new house pics start at around the 10th album or so.

http://community.webshots.com/user/rubikscube

Cool. I was hoping you'd do that!

It's not really a good dream house, more of a "dream cottage".

When we were laying out the floor plan the builder asked if I wanted the foundation stepped down for a home theater.

I looked at him like he was from another planet. "Why the ^*%$*&% would I want a theater in my house ? I have a 27" TV, not a projector and an 8 foot wide screen". Live and learn, huh ?

Even Dilbert's Ultimate House (DUH !!) has a dedicated home theater with tiered seating:

I don't know how I've managed to miss this thread thus far....John, man that is really one nice setup you have going on there, it's amazing how that single fireplace can heat your whole house. Nice!

Thanks, Rick. If you saw the fireplace in person you would be less surprised it can heat the whole house. After all, it *is* 7-1/2 feet tall and weighs about four thousand pounds not counting chimney, hearth or foundation

The night I fired up the masonry heater for the first time, I had some friends visiting. Part of the purpose of the visit was to try to recreate a specific German rye bread they liked. They ended up staying the night, and I made some sourdough english muffins in the morning which were a big hit. At the end of the visit, they asked me for some sourdough starter, so I split some off, fed it and sent it home with them.

I asked a few days later if the starter had survived the trip home -- the answer was a curt "no, I'll explain later", which seemed really odd. It wasn't a great starter but it was pretty tough -- it's survived me for at least 6 months now, including being left in both very hot and very cold cars, so I was surprised that my friends (who are smart, careful people) had been able to kill it.

Well, I got the story tonight. Turns out that when they left my place they put the starter, in a tupperware container, in the back of their Jeep along with Kingston, a large chocolate lab (retriever).

When they got home, the tupperware was empty and very clean.

Erp !!

Well that solves the mystery!

Very entertaining story, thanks Bridgeman.

In the "oh my god" department... very interesting link here by a gentleman who spent the last six years trying to duplicate the taste of his favorite New York pizzeria. One of the many critical steps turned out to be jimmying the interlocks on his oven so that he could open the door during the self-clean cycle, giving him the 800+ degree temperatures needed for that authentic thin, crispy crust.



http://www.sliceny.com/jvpizza.php

Ah yes, man's best friend. I remember one night, after working late. I was feeling poorly, exhausted and starving. Nothing in the fridge so I ordered delivery from a Mexican eatery which delivered (at a premium). I was in dire need of comfort food and didn't feel like going out at all. Shortly after it arrived, around 10pm I finally sat down to eat in front of the TV, but before I could take my first bite, the phone rang in the other room. When I returned to finally dive into that tasty beef enchillada dinner, It was gone! The dish was licked totally clean by none other than our trusty spaniel "Scooby".

If she wasn't the best dog I have ever had the pleasure to own, at least until then, she would have been found along a deserted road somewhere.

Live and learn...

Outside of a dog, a book is man's best friend.

Inside a dog, it's too dark to read.

Oh I gotta use that one, Tom. Beautiful! I'll try to remember to give you credit, though.

Ya know Tom, you have a point there. You don't have to feed them, walk them or clean up after them when they just decide to take a zap when ever they feel like it! AND a book won't eat your dinner!

Oh, don't give ME credit, Jack. I can't even remember who I stole it from.

Good to have you back, JP. I should've recognized that as a "Grouchoism."

>>When I returned to finally dive into that tasty beef enchillada dinner, It was gone! The dish was licked totally clean by none other than our trusty spaniel "Scooby".

Have some sympathy for the poor dog. She probably burned her mouth eating "the food you left for her"

I don't know about her mouth, but I do know that it didn't agree with her GI tract! What a mess...

Yeah, apparently there was more than a bit of "excess flatulence" after Kingston sucked up the bowl of sourdough starter ;(


Heater update -- still running tiny little fires while the masonry curing completes, but right now it's 37F outside and 67F inside, running two small fires a day. Once the masonry is dried out I can go back to running one larger fire a day.

A typical fire right now is 4 typical pieces of firewood, albeit 12" long rather than the more common 16", with each piece split in two, plus a bit of newspaper and kindling, so I'm using about 8 pieces of firewood a day to heat the house.

The measured temperature around the corner from the heater was 72 degrees with the furnace fan turned off and just the ceiling fan going, but I found some of the most distant rooms and the basement were getting chilly. When I ran the furnace fan for a while the measured temperature dropped to 68, ie that was the average temperature of the house once the variations were evened out.

Once everything is dried out and operating normally the heater will be able to take maybe 4-5 times as much wood as I am burning now in a single firing, so I'm still hopeful that I should be able to heat the house with one fire a day for most of the winter.

>>Or, would you have to walk around in your boxers for three days because the place is too hot?

Well, it happened. I'm running a series of ever-larger "curing fires" to dry out the heater core and stonework. I'm at the point where the curing protocal calls for 4 small fires a day with some cooling off time in between. The cooling off is for the inner surface of the flame channels, but the masonry mass keeps storing up the heat and getting a bit hotter with each fire -- the result is like running a fairly large fire each day.

As a result, it's too damn hot in the house. I have a bunch of windows open (it's high 40s outside) trying to get down to a liveable temperature inside.

Sounds as though the Masonry Heater is getting the job done John, as hot as it may be now with 40 degree weather think about how effective that baby is going to be whenever things really start to cool down outside ... which, by the way in my neck of the woods 40 degrees is dead middle of the winter freezing.

Now if we could somehow get a 'Masonry Air Conditioner' to help alleviate some of our cooling cost!

So... I didn't get a chance to post during the coldest part of February, and I wasn't around the house much in the evenings anyways, but we did get a few weeks where the outside temperature was around -15F (say -22C) at night.

When I ran two medium sized fires a day the outside of the heater stayed a lot warmer and seemed to keep the house around 60F when the outside temp was -15. I think if I had been around enough to split more firewood and get 40-50 pounds of wood in each fire (vs. the 25-30 pounds I normally burn) it *probably* would have kept the house comfortable on two fires a day.

It's warming up now so I guess I won't know for sure until next winter.