I've been scouring these forums on and off for maybe 2 years now since I was first introduced to RMH's. Everyone is nice and so knowledgeable, give yourselves a round of applause!
Short story: I want to start doing my homework here and I was wondering if anyone could point me in the direction of a remote rocket mass heater (in a garage 40ft from the house) that could heat my home (1500sq ft) via copper coils on the heat riser, pex off a manifold, and radiator/heat exchangers inside the house.
Long story: So I'm a newbie and considering my first rocket mass heater build. I'll probably make one or two concrete ones in the back yard just to get a feel for it first. I live in a friends house that is being foreclosed on. They moved out to be closer to work but their real estate agent suggested that they have someone live at the house so squatters don't settle in, pipes don't freeze, they property is maintained, etc. That's me, I prefer to refer to myself as the curator. It's a pretty good gig. I've had a free house to live in for just over a year. I only pay the utilities. That's where the problem lies. The owners have installed a new gas furnace the year before i moved in (this house was built in 1890 by the way) and I thought "great! super easy gas bill!" I ended up paying about $2400 in gas bills from November to April give or take. I thought if I could build a system and fuel it with wood for a fraction of the cost and gain experience in building and running a system like this it would be great. The bank may be getting involved soon as there was a lis pendens served in August. Which means I could have real estate or bank visitors soon. Obviously, it's not my house so I wouldn't build a giant cob bench in the living room. Given the circumstances, my thoughts were this... build a small (30gal drum for the riser) RMH in the garage, just outside of the house with durock concrete board surrounding the RMH, or possibly a small RMH on a heavy duty utility wagon that could be rolled in and out of the house? I would like to use copper coils around the heat riser to capture the heat. The hot water would then run through +/-40ft of pex tubing from the garage to the house (insulate the pex somehow?) and into some type of radiator or heat exchanger ssytem? Keep in mind, I may be having visitors from a bank soon who may decide my fate in my free house, meaning they might let me continue to curate during what could be a lengthy foreclosure process or the might give me a definite amount of time to vacate...pissing these people off with not so legal RMH's and pex and radiators around the house when they come to inspect is not what I want... So I'd like to keep the system portable if you know what I mean...hence the wagon idea...
Sorry, I'm afraid you're crazy If a gas furnace cost $2400 to heat your 1500 sq ft house, it is quite leaky and needs a lot of heat. An RMH built into the house and radiating/conducting directly to you and the furniture could work, but the multiple inefficiencies and losses of conversion from fire to water with long outdoor runs to radiators would require a large system, maybe more than 8", and I don't know how much you would actually save.
My guess is that your best return on effort would be to tighten up the house - extra window coverings, find and patch air leaks, etc. Adding insulation in walls or roof is probably not in the cards. What is the character of the basement? That may be a major source of leaks in an old house.
A portable RMH on a heavy-duty wagon that can roll in & out of the house may be a good option. Is there a separate chimney you could connect it to (not the gas furnace chimney)? How strong are the floors where a wagon might roll?
posted 5 years ago
Glenn- Thanks for the response! Yes, this place is definitely drafty. I think I might go into the basement and use Great Stuff to fill in any cracks. I'm thinking about using the frost king plastic on both the outside and inside of these old windows? There's an old wooden bulkhead which I am sure isn't doing much. I have been toying with the idea of putting straw bales around the foundation to block some of the draft. Although, some say it's a nice nest for mice which are already an issue in the winter.
As far as the floors, it's an old house. The hard wood floor sag a bit but are in much better shape than some other houses ive lived in. I wouldn't know how to gauge the strength of the floor itself? The foundation of the house itself is brick.
There is no seperate chimney. I was hoping to use a window? These heavy duty utility carts I see for sale at the big box stores have ratings between say 400-1000lbs. Would that be enough to hold the weight of the RMH?
Location: Upstate NY, zone 5
posted 5 years ago
Your proposed window and gap treatments sound good. How much does the floor bounce when you jump on it? If not much, you are probably good for a temporary load.
The utility carts are pretty good, as long as you keep heat away from the tires. The volume of say 600 pounds of masonry with cavities could reasonably fit on the deck. You should be able to fit a compact 6" system with a small masonry bell on one of those, and maybe arrange it so that you can pile 4" solid concrete blocks around or on it when it is in place for use. A standard RMH has several tons of mass, but you can still benefit from a smaller amount. You may want a higher exhaust temperature to get draft in a temporary chimney anyway.
Running a vent out a window is possible, as long as you can get an insulated chimney up above roof level. Without a good chimney, you will probably get a considerable amount of smokeback in the wrong winds.
posted 5 years ago
Glenn- There is a roof over the 1st floor on one side of the house. Would this be acceptable? I have a hard time imaging how I would get above the second floor without tying in to the existing chimney(which I don't think is recommended?). I'm in a pretty residential area as well and it might look "funny" running a two story chimney from a window? Or is there a way you can create a box around the chimney to block wind?
As far as keeping the tires from getting hot...my initial plan was to line the deck and sides of the cart with durock. But now that I'm thinking of it I'm not sure that durock "reflects" heat like I initially imagined it would... any experience with durock or anything else that might reflect the heat away from the tires?
Floors seemed to pass the bounce test...
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