Hi permies. I'm planning to build a 6 inch rocket mass heater inside of a barn here in the sierra foothills. I'd like to run my ideas across all of you here on the forum, and then I'll likely document the build here as well. I've built one other 8 inch system, pretty much just following the layouts and directions in the rocket mass heaters builders guide, which I'm using to help with this one as well.
Some pertinent information:
We are at about 2700 feet with a mild climate, average winter low around 32f, sometimes down into the 20s.
The building is an uninsulated barn, with old board and batten siding with holes everywhere, definitely not air tight. It's about 2100 square feet, including the stalls on the perimeter, but we would really only be aiming to heat the large center room which is about 600 square feet.
We are turning this center room into a shared community space, and we would like to have a warm place to spend time together. I'm thinking to go with the heat the people not the air strategy since the building isn't insulated, thus the RMH.
I'm planning to go with a 6 inch system, primarily because we already have most of the triple wall insulated stove pipe for the exterior chimney, and that stuff is quite expensive. I'm also considering using a bell stratification chamber in the mass bench, made out of 55 gallon barrels cut in half lengthwise, since even single wall stove pipe is expensive and I already got some barrels for free.
The placement of the heater core is pretty much limited by the doors to the outer stalls and the easiest place to get a chimney outside. There is small gable end wall between a higher and lower section of the roof, about 3 feet tall. I'm thinking I can run the chimney pipe either horizontally or diagonally through this end wall, high up near the peak of the roof, and then 3 feet above the ridge. I know that's not the ideal chimney, but I would rather do this than punch a hole through the nice metal roof I just installed. Given that the building is so full of holes, I'm not too concerned with a competing chimney effect, and I'm bringing the exit flue up right next to the barrel to help pull the gashes up and out.
Even though the room is quite large, about 20x30, because of the doorways there is only a 7' x 10' corner in which to build the core and bench. You can see in the sketch ups below the configuration I came up with. I positioned the core where it is in order to get the 30 inches recommended clearance between the barrel and the plywood walls. I'll probably still put up a heat shield.
Is there anything you can see wrong with this design? There's some pictures and sketch ups of the heater below, and the sketch up file itself if you want to look closer. Thanks for your input!