Rocket Mass Heater for my home

[Lollykoko]

That is a lot more space than I had thought, given the size of your benches.

We are talking about putting RMH in the bedroom exterior walls, the sand bags being the necessary mass. The walls will be insulated from the hillside around them. My sister and BIL like things a lot warmer than I do, so multiple heaters gives us more options, I think. Of course there will be one in the family area that heats the floor, (if the plans I'm finding are workable for us). I'm wondering if I can use one to replace the electric heater in my waterbed, by creating a depression for the mattress with high cob sides to prevent blowouts.

Do you have any plans for decorating your bench once the cobbing is done?

[matt walker]

Yeah, it is a big space. If it wasn't over a basement, I would have WAY more mass, for sure. As it is, I think I have the bare minimum mass, due to the limitation of the weight and space. I like the waterbed idea! I bet it would work well. I have had some thoughts of decorating, but I still think that after living with it for a year or so, if I continue to love it, I might still finish it with brick like my original sketch. It would be nothing to chip the face back a bit and lay a few courses of bricks to contain the mass and make up the benches.

[paulbee]

Matt,

This rocket mass heater is a beauty!

I am interested in duplicating it. Why recreate the wheel, right?

Are you still impressed with it (know we aren't in the winter heating season now)?

Did you conclude last heating season still burning less wood than with your boxwood stove? Did the temperature constant continue after you burned the cob moisture off?

[matt walker]

Thanks Paul! Yeah, I'm so extremely happy with it, I still shake my head at my old way of heating with the box stove. I can confidently say I burned easily half as much wood as I used to, and I suspect way less than that even. The house temperature was much more stable than it's ever been. I was typically waking up to 62* or so when the outside temps were in the 30s. Running the stove for a couple hours in the morning and evening would have the living space above 70* in fairly short order, and of course the bench was always warm. Sitting or laying on the bench is just wonderful. It leaves you warm to the core. I had a great winter thanks to the stove.

I should say that after Oddmar's troubles with the fireclay casting I wonder about advising this construction method. I am extremely pleased with mine, but you should know that the fireclay/perlite mix I made my core out of is extremely soft. If you have ever felt a light fire brick, the kind used to insulate kilns, you'll know you can break it apart in your hand. That's how the core will come out, soft, fragile, but extremely insulated. Mine has been performing wonderfully, although it shed some chunks here and there. I think it is a superior burning core to brick, being so insulated, but you need to accept a rough finish and the possibility of needing to add to this "liner" with handfuls of clay/perlite down the road. I'd do it again for myself for sure, but on the other hand, check out Oddmar's stove. His core is really cool and will last forever.

The best advice I can give is to just start playing with 'em in the yard. It sounds from your post in Permsteading that you are familiar with cob, so I wouldn't even worry too much about the makeup of the clay or longevity. Just make a quick mud stove outside and start playing with it. You'll quickly get a handle on how it all works, how it holds up, and what you think will work for you.

[matt walker]

Well, I finally made an update video. Here it is, from yesterday. Go easy on me on the latest plaster job, it was quite a Learning Experience!

[GrahamB]

Thanks Matt. I just showed your video to my wife. She pointed to our Ashley wood burner and said. Build me one, just there. As if I didn't have enough to do. That was impressive, my friend.

[matt walker]

Thanks Graham! I like the way your wife thinks, better get to it. That stove ain't gonna build itself!

[Lollykoko]

Matt, I get the feeling that the color isn't exactly what you were hoping for. What sort of options do you have to color the plaster as you work? Are there powdered dyes to add to the process? Could you add paint from the "Oops!" bin at the home store before the plaster goes on?

My local big box home store has been featuring tan porcelain tiles at a great price. It might be worth buying enough to tile the tops of the benches I have in mind.

[pa_friendly_guy]

When Graham builds his stove Matt would you recommend using the 1/2 Barrel design or do you feel that the ectra mass in the bench with just the stove pipe through it will hold the heat better on those long winter nights? I have always felt that the extra mass would be better, even though it might take longer to heat up. The 1/2 Barrel would take less cobb, and therefore it would mean less work in my opinion. But since I have not made either of these 2 types of stoves, I value your opinion a lot more than mine, let me know what your thoughts are on the 2 different stoves.

[GrahamB]

Good point there Guy. It got me thinking that maybe there could be a compromise. Instead of using the 55 gal barrels, how would it work with smaller barrels, say 20 or 30 gal. Would the lighter gauge metal they are made of be a problem? Then you could still have quite a bit of mass in there.