Sunday, November 15, 2015

Rocket Mass Stove LIFT OFF!



Grandson Wesley helping out.
 We've been inside the grain bin house for almost a month and although we continue to whittle away at projects big and small (painting my office!) it feels like progress is slow. But, as of last week, we have non-electric, non-gas heat. The rocket mass stove had it's initial lift off last Sunday and we are still here to blog about it.

After planning our stove we realized we were a brick short. (Insert rude blog follower comment here)Finishing it involved creating a brick out of mortar in order to build the heat rising to the appropriate height. Below is a rare photo of me at work. In this process Keith and I quickly learned we have no talent for brick laying. Not an easy job. Dear Jay, you have all our respect.

We then covered the brick heat riser with Kaowool, an insulating material used by those in the refractory business. Dear Jay, you were right, it worked perfectly. To keep this material in place we wrapped it with hardware wire and pulled the ends together at the top. The goal is to keep the gasses flowing up and out of the heat riser keeping this path clear to avoid areas where ash can build up.

After putting the grandson to work with a wire brush on the steel barrel, we placed it over the heat riser. It is not exactly center as we needed to not cover the wood feed channel on the right but we did need to cover the entry to the floors stovepipe network under the concrete.

Once we had it where we thought gases would flow best, we attached the barrel to the floor with cement and let it dry. We sealed the top of the barrel with a fire resistant gasket glued in place with even more heat resistant silicone, and clamped the top in place. We let everything cure a couple days then with two of our boys close by (the fire department on speed dial on their phones) we lit her up.

As predicted by Ianto Evans the author of Rocket Mass Heaters, it took awhile for the new stove "to learn it's job." There was some smoke, ok massive amounts of small that sent our family screaming out the door, as we played with draft, opening and closing windows, blowing on the flame manually, blowing on the flame with an electric fan. Yes, a small amount of the plastic fan covering did melt. What's your point? It took much of the afternoon  but then after everyone else left, the rocket mass stove behaved itself.

The barrel does get very hot when the fire is burning and will boil water. After the fire is out the barrel stays warm for about 18 hours. Great for rising bread, warming buns, keeping foods hot while cooking on the main stove. Since then we have fired it up 4 times. As a rule it heats our small home in an hour bringing the room temp from 63 to 70. One day it brought the room up to 80! If we run it three hours, let the flame burn out, and its mild outside and not windy, it will keep the house warm for 48 hours. A couple of days ago we have 50 mph winds so we had to fire up the stove again after 36 hours. We are guessing in the real cold of this Midwest winter we'll need to run it at least 3 hours out of every 24.

We were thrilled to feel the concrete floor heat up, and stay warm after the fire went out. Even 36 hours after it has run the concrete is comfortable to walk on. No socks needed. We've also learned that round sticks are best. Flat pieces of wood don't burn with the same consistency, often too fast and they burn up the feed channel instead of across it and smoke. We start with small twigs, advance to pencil size sticks and then to larger 2-3 in. diameter pieces of old wood. All of it is already here on the property, tons of dead trees just waiting for us to "harvest" them, with clippers, not an ax. Easy work.

It continues to be a learning process but for the first time in our lives, we are now free of heat related gas bills. That bit of freedom will get us through any little glitch we may still discover with our new Rocket Mass Heater. Special thanks again to Ianto Evans and Leslie Jackson for their great book. Be sure to check out their website Cob Cottage., and our friend Jay Molter of Molter Corporation for all the excellent building materials and how not-to-die-by-fire-advice.

Hot coals in bottom of feed chamber and flame burning to left
towards steel barrel, as it should.


  1. Wow, sounds very impressive. Do you have an open fire too btw? I have to admit I am a sucker for heat from the fire.

    1. No other fire Lorna but although we have to get up and look down into the feed chamber to see the flames we can still hear it crackling from other parts of the kitchen.

  2. 3 hrs, thats nothing and hardly any fuel at all. This is really going to work. Well done, you two!

  3. Replies
    1. Hey Reno, may I call you Reno? Thanks for the praise.

  4. Hokey Smokes, Bullwinkle. Look at you weild a trowel! You go girl. So glad the stove figured out what it was supposed to do and I'm truly envious of warm floors. Say, how easy is it to clean out the ashes way down in that pit and how often do you have too? Will the steel barrel last a long time (like, hopefully, forever?). And, yes, I was the 'girl in the back, what's your question?' in class. LOL Thank goodness you're warm now that the temps have turned. Congrats!

    1. Hey there Natasha or are you squirrel? I always loved Natasha...anyway, the feed pit in about 12 inches deep and easy to clean with a shop vac which I have been doing every other burn or three times a week. I probably don't need to we are just being extra careful while we learn.The barrel is expected to last at least a year, maybe several, the sources all say it varies on how often you fire it up, for how long and how hot. I still hate the color and may paint it with a high temp paint. We'll see. Keep the questions coming, I was always the girl at the front of the class with all the (mostly wrong) answers!

  5. So, I see that the system misbehaved while you had the largest audience and then settled down to do its proper job after most had left.

    I'm a bit envious that you don't have a heating bill. Very glad for you and Keith, oh that I could do likewise! But, i'm grateful that I'm employed so that I can pay the heat bill.


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