Freaking Out

Hi All!  

I am having a RMH fabricated for me by a guy from Etsy who builds them.  When I asked him a question about RMH's, he referred me to permies, which is a great sign I think.  Anyway, I listen to the podcasts all day at work so I guess I'm a pod person.  Listening to everyone talking about all of the RMH experiments that didn't turn out, or people who don't know how to start a fire or use the heater correctly makes me worry.  I have 30 years of experience with regular wood stoves to heat the home.  Somebody, please tell me that everything is going to be ok LOL.  This will have a J box and will arrive ready to install, like a Liberator is ready to install.   Also, what would you use under and behind it for the hearth?  I already have cement board (yes, I said it, CEMENT...sorry LOL), and then I have tile or corrugated metal. Which choice is safest?  There will not be any bench, cob or pebbles etc....the house is too little and it would collapse the floor anyway.   My house is a 500 sq ft 1958 mobile home like I love Lucy "The Long Trailer".  

Hi Brooke, Welcome to Permies!
I'm not sure, but if you're not having a bench or bell then I think you're having a rocket stove rather than a rocket mass heater. The bench or bell are the 'mass' part of the rmh. Are you going to use it for heating or cooking?

Welcome to the world of rocket mass heaters! You will love not having to have a fire going overnight to stay warm, and the small amount of wood you will burn.

How tricky your system is to operate will largely depend on how good your setup and chimney are. Do you currently have a woodstove and chimney? What sort of chimney are you going to be using? Insulated metal I would presume, with a mobile home. How tricky was your most recent woodstove to use? If you are using the same chimney, I expect you will have a similar RMH experience. It used to be a selling point of RMHs that you could just stick a pipe out the wall, but that kind of setup is the kind that experiences finicky behavior. For good reliable draft, you really want a chimney built to code: insulated, preferably going straight up through the roof, and terminating well above the ridgeline. I have never had to prime my chimney, and I currently have it going out the wall and up; when I do the nice internal two-story stone-faced masonry chimney, I think the draft will be even stronger.

Can you tell us who is building your RMH? If it is in one piece for simple installation, and going in an old mobile home, it obviously can't be very heavy. Therefore it probably won't be able to store enough heat to last 24 hours, but it could well last 8 to 12 hours so your place can be comfy overnight or while you are at work. Once you have it warmed up, it won't take a lot to make it very warm again, maybe one loading in the morning before you leave so it is easy to get cozy soon after you return.

One of our experienced members, Chris McClellan "Uncle Mud", has a design called the Cottage Rocket which fits in a 55 gallon drum including some mass. It sounds like you are getting something like that.

What sort of protection you need under and behind your RMH depends on the details of its construction. If it includes some insulation in the base, you might be fine with a sheet of cement board under it, but it would certainly be safer to put some bricks under it with air space between them so the bottom can be ventilated. Letting warm air from the base circulate in your space rather than warming the floor and the crawl space below is beneficial too.

The back protection depends greatly on the design - it could vary from 8" clearance and a sheet of metal on spacers to 24-36" clearance and a full metal shield as for a woodstove.

Hi and thank you for the replies! Yes I have heard about the cottage rocket and it sounds similar. I am going to post the link but the link is to a different model he made, which was portable and burned pellets.  I don’t want to burn pellets, we have tons of free beetle kill around here to burn.

The chimney:  I will be installing specifically for this heater.  Triple wall.  And installed properly to be 36” above the “peak” of the flat roof. There will be one elbow only, attached where the pipe comes out of the heater.  I’ve installed chimneys before, with great draft.

The heater weighs about 300 lbs. Luckily I work for excavators so they can bring it over to my house with a skid. Old mobile homes like mine are solid as fuck, real wood, and steel, and all wood interiors with built ins…no osb floors to fall through (been there, different trailer).  It is also very small so there are beams close together under the house (the frame).  My house also still has the original tires and wheels on it LOL.

Ok let me see if I can figure out how to post more attachments to this thread.