I’m going to build a 22x24 garage/shop and install a RMH in it. What things do I need to incorporate into the design to accommodate the heater? For instance, should I have some of the foundation wall built up to 2’ as one wall of the heater? Ordinarily, I would be doing my research before asking such a newbie question but I’m under a time crunch to submit my plans to the building inspector and just stumbled on the concept of RMH. Too bad I can’t have this heater for my house!
Thanks in advance for your help.
Insulating under the core / mass is probably the most important thing at this point. Is your slab already going to be insulated ? Were you thinking a long mass or a tall bell ? You do not want to build up a stem wall as part of your mass. In fact you want to be insulated away from any outside wall or ground contact.
I am installing a bell type rmh in my shop this summer / fall . My slab is not insulated from the ground so I used 2" EPS foam board . leaving my side insulation so 2" or more of concrete will cover all the foam and the hardy board comes up to grade height to ease screeing and will isolate the insulated portion of the slab from the un-insulated.
In quickly looking at Eric Hammond's pictures it looks like I can insulate on top of an existing slab. I started out assuming that all RMH was a long bench type design. After I get the plans for the garage off to the building inspector I'll have time to do my proper research on this site. Having said that how far away from an exterior wall is the burn chamber? Should I assume the same distances that one would use for a wood burning stove? I feel guilty asking questions that are probably answered on this site.
This site is going to be dangerous for me because I'm going...I want to do that..and that..and that... Is there going to be a seminar on building a RMH anytime soon someplace in the west that I can attend? I live 2 hours north of Seattle.
Sorry for the delay. Yes , you can build on top of an existing slab and insulate between, same as Eric has done. Originaly rmh's were a long mass, current rocket science has options, including bells and ceramic fiber boards and blanket. You will want to do a lot of reading here and at the Donkey pro boards for the latest innovations.
Yes, treat your core and barrel like a wood stove. Only the barrel will be at super hot temps, mine can run 1100 F on top and the sides average in the 500 F range , the core outside temps generally stay below 200 F on my stove. The mass only needs a min of 4" insulation from an outside wall . Outside temp on the mass will be around 100-150 F . Your stove pipe where it leaves your mass will be apx. 130 F The feed tube should be protected from wood areas as can be.
As far as seminars, Most get advertised here at permies. Ernie and Erica Wisner are in the okanogan valley just over the mountain from you. They are recognized leaders in rmh building and design innovation. Their book " The Rocket mass heater builders guide" Is the current best book to own if you plan on building a rmh.(readily available on amazon) They also would be the best place for you to find a class being put on. Erica could be reached with a purple moosage here thru permies.