New to Tulikivi...

[AKguy0524]

Hello! I'm in the final stages of buying a home that contains not one, but two Tulikivi stoves! It has a model TTU2700/5 and TU2200T/51. The house is 5,000sqft. and ICF construction. It is in central AK where the winter temps typically hang around 0 - 25 above with a few weeks every year of below zero. The two Tulikivi's are located on the first floor where there is a concrete slab, but there is an upstairs as well. My question for anybody in the know is just how efficient are these at heating large spaces? The home's primary heat system is a hydronic in-floor system with an oil boiler. Being the fact that oil is what it is, I'd like to use as little as possible. Everything I read online about these stoves says they are amazing, but I'm just wondering will they radiate even to the upstairs? The previous owners are out of the picture and I can't ask them for any help/advice, but I did see oil receipts for 2 years with no wood supplement used and their heating oil averaged $800/mo. Again, that's with no wood being burned. So I'm wondering, if I use the Tulikivi's regularly, one, maybe 2 burns/day in the winter inside of an ICF home, how much could I expect to reduce that monthly oil cost?

TIA!

 

[stoveliker]

Unless their stone construction goes thru the floor they won't radiate upstairs.
But air might convect upstairs thru stairs etc.

This depends on the layout of the home.

 

[John Lehet]

I had a tulikivi for 15 years. I loved it!! It absolutely heated the whole house perfectly evenly. You are lucky!

BUT I had a superinsulated small house with a small heat demand.

Tulikivis do not have a high BTU/hour capacity compared to a big modern wood stove, so if you have a huge heat demand these may not heat your house. You could build two or even three fires a day I guess and push it. I only built one fire a day, very rarely two.

The tulikivi was perfect for me since I could burn wood, which I had plenty of, and distribute the heat from maybe 20 or 25 pounds of wood over 24 hours in that house with low heat demand. I made a fire once a day. If it was sunny and not below zero, sometimes I could skip a fire. The temperature in that house stayed quite even. My heating with the tulikivi was often as much anticipatory than responsive. I looked at the forecast, planned for the heat demand of the coming day.

I burned almost all poplar. There were always poplar trees either falling down or begging to be cut down at my place. The poplar was perfect, because it dried well, burned hot and clean, didn’t coal much at all. I had a full closer damper, so as soon as the fire was burned out — an hour or hour and a half or whatever — I shut the damper all the way closed to keep the heat from going up the chimney.

You want wood that is dry and split small. I also burned a lot of small rounds. You don’t want, I don’t think, a long lasting fire with big logs. That might work OK and I might be wrong, but that didn’t seem right to me.

I built mine myself, with my ex, one weekend in 1986. It was, as far as I know, one of the first ones built in the US. I got to watch the first one in Vermont get built, so I had some idea what was what. I got it super cheap, a demo model, testing the import market. It was 1986, no internet. The manual — building and maybe using — that came with it was all in Finnish. Nobody here knew anyone who spoke Finnish, and no way to translate it.

One resource that I had for the general concept, and you should read is The Book of Masonry Stoves, by David Lyle. I think I’ve got title and author correct from memory. It’s out of print, but I think the internet archive has a copy of it.

My Tulikivi experience, with 3500 pounds or whatever of soapstone, made me think that soapstone wood stoves were just a gimmick and a scam. But now I have one, and I see I was wrong. I very much burn my Progress Hybrid like a mini Tulikivi except for the letting the fire go all the way out part. But I heat in bursts, let the stone get hot, and coast on the last fire for hours until I start the next one from coals.

Tell us more about the house, maybe I can tell you more about heating it.

 

[John Lehet]

Re reading your post, I’m thinking I should add that you definitely want to think in terms of anticipation of heat demand, and use either the Tulikivis OR the oil, Once you get one hot, then getting the other hot at the same time might cook you out. It’s going to be a big thermal flywheel, and you’re going to have to get to know it and watch weather forecasts. You might be able to dovetail a bit, light a fire as the slab is starting to cool down. But you’ll have to get to know that.

I moved from the Tulikivi house eventually to a house not superinsulated but with better than average insulation, and with hydronic heat through a slab downstairs. Also had a little woodstove there. If I was going to use the wood stove, I had to anticipate that, and turn the hot water heat off ahead of time, let the slab start to cool, so the stove didn’t add to the already warm enough house with a lot of momentum in the slab.

I was professionally very busy in that period and had two kids for which I was primary caregiver. The stove I had turned out to be the most horrible, in my view, stove I ever had, a VC intrepid. Cute, but difficult. I was hesitant to say to the family, “OK, I’m going to get it cool in here so maybe I can get this stove to work.” So really I didn’t do that much. I didn’t like burning oil, but that’s what we did mostly. I was only there for about three years.

 

[gthomas785]

Oil is 140k BTU/gal and wood is ~15k BTU/lb depending on species and dryness. If you burn 100 lbs of wood every day, you'd offset about 11 gallons per day of oil use assuming the heating appliances are similar in overall efficiency (no idea if that's the case, but it's a starting point)

 

[John Lehet]

I’m not sure a Tulikivi is meant for 100 pounds a day of wood, but between two of them you could maybe push it that far.

I definitely used to weigh my wood back then, just to have a sense of how big a push I was going to give the thermal flywheel.

Part of the efficiency equation of a masonry stove is that the masonry isn’t warm when you have the fire. Therefore it is able to absorb heat from the firebox and smoke path very efficiently. If the stove is already warm, it won’t do that in the same way. So the cycle is a cool to lukewarm stove gets the hot fire, and the stove slowly gets warm.

 

[John Lehet]

I don’t think you end up with 15k BTU/Lb of wood by the time it goes through a woodstove though?

 

[gthomas785]

I don’t think you end up with 15k BTU/Lb of wood by the time it goes through a woodstove though?

No that is the energy density of the fuel. Same with oil - what you get out depends on the efficiency of the appliance as I mentioned.

100 lbs was just an example. I don't know what the intended BTU output of these things is. I routinely load 30-40 lbs of wood into my vc encore which is a medium sized stove and I would do that 3x a day when it's cold out.

 

[begreen]

25 lbs of wood, twice a day, in two fireplaces in a super large house, in Alaska? That sounds possible, especially in very cold weather.

 

[stoveliker]

You don’t want, I don’t think, a long lasting fire with big logs. That might work OK and I might be wrong, but that didn’t seem right to me.

You don't want long lasting fires, as then more heat escapes up the flue. Burn fast and hot (so clean), and no coals, so you can close the flue to avoid the stones radiating back into the flue and having the heat flow up out out.
Closing the flue can only happen after coals are gone for CO reasons. So coals are not ideal.

 

[begreen]

Hot fires, twice a day is how my friend runs his Tulikivi.

 

[Todd]

Lucky guy! I sure would like to try out a Tulikivi in my place especially with this cold below zero weather we are having right now.

With an $800 per month oil bill I’d definitely be burning wood 24/7! From what I’ve read these heaters act like a little sun. You feel the radiant heat in sight of the heater. Go behind a wall and it’s like stepping into the shade. There will still be some natural convection and the heat will rise. How much it will heat your upper level is hard to say. Keep us posted on how it works out.

 

[John Lehet]

I haven’t had my Tulikivi since 1998 so maybe I don’t remember perfectly, but I feel like the Progress Hybrid is even more powerful a “sun” in radiance. The Progress is warmer than my Tulikivi ever got. Probably I ran my Tulikivi cooler than many people do, since I didn’t need a lot of heat. I only had two hot spots that sometimes got too hot to touch, while the Progress is always between 200 and 350F on the stones.

 

[Todd]

I haven’t had my Tulikivi since 1998 so maybe I don’t remember perfectly, but I feel like the Progress Hybrid is even more powerful a “sun” in radiance. The Progress is warmer than my Tulikivi ever got. Probably I ran my Tulikivi cooler than many people do, since I didn’t need a lot of heat. I only had two hot spots that sometimes got too hot to touch, while the Progress is always between 200 and 350F on the stones.

That’s something I have a hard time understanding. How can a masonry heater heat your space when it’s just warm to the touch? A day like today when my high is -10 I just can’t see how something could heat my place when the stones are 150 degrees. I know it has something to do with all that thermal mass but it’s hard for me to wrap my head around that. I’ve been feeding my stove every four hours to keep it 350-650 degrees.

 

[stoveliker]

It's the surface area.

A much larger area radiating less per sq ft gives the same BTUs as a smaller area at a higher temp.
And the consistency for hours. (This seems also to be a factor in low output BKs that do so for 10s of hours.)

 

[gthomas785]

It's the surface area.

A much larger area radiating less per sq ft gives the same BTUs as a smaller area at a higher temp.
And the consistency for hours. (This seems also to be a factor in low output BKs that do so for 10s of hours.)

Just like how heated floors can keep your space warm with only a 70-75 degree surface.

 

[John Lehet]

When I had heated floors, they only really felt warm to the foot when it got below about 10F out

 

[EbS-P]

That’s something I have a hard time understanding. How can a masonry heater heat your space when it’s just warm to the touch? A day like today when my high is -10 I just can’t see how something could heat my place when the stones are 150 degrees. I know it has something to do with all that thermal mass but it’s hard for me to wrap my head around that. I’ve been feeding my stove every four hours to keep it 350-650 degrees.

Our bodies are really good as sensing infrared heat. I can walk by my fireplace and stove and feel the heat when it’s just 15 degrees above room temp 12 hours after I saw the last glowing coal.

It’s really all about surface area. Remember radiated energy scales with temperature to the 4th power! So a little change in temp gets a much much much much bigger change in output. So the surface area is easily 5 maybe even 10. times as large as a stove.

 

[AKguy0524]

Dang, great feedback everybody, thanks! I'll have to report back once I get the house and try these bad boys out!