Josh Hoffman wrote:I have been considering building a rocket stove. I have the E&E materials to do so and have read a lot on masonry heaters.
I am not sure if I am willing to trade the enjoyment/non-efficiency of a fireplace for some other apparatus. I have acreage and part of the acreage devoted to a woodlot and I enjoy processing firewood. Having recently been studying " A pattern language", I am not sure I want to sacrifice the enjoyment I get from a live fire in full view for the efficiency of these other ways.
I haven't (yet) built a
rocket stove, or any other thermal mass heater, either, so maybe I
should butt out.
However, it seems to me that you probably need to decide what your objectives/needs might be, and the relative weight of those objectives, both for having a place for fire, in general, and the possible rocket heater, in particular.
I see that you are located about 200 miles inland from the Gulf of Mexico, at around 1000 feet of elevation above sea level. Your USDA zone indicates that you have a long growing season, with a comparatively short cool season. I'm sure you really do need the heat for practical reasons sometimes, but cooling is probably more important than heating, for much of the year. I tried to find a weather station either reasonably close to Louisville, or as a reasonable proxy, but most of the weather stations near you are at lower altitude (Starkville and Jackson and so forth).
If a person was burning 8 or 10 cords of
wood per heating season (or even more) in a plate steel box stove, and has dropped that down to less than 2 after implementing a thermal mass heater, the return on the investment is pretty significant. In your case, you are probably already burning "1/10th the wood" of someone using a conventional stove for primary heating in my neck of the woods, so the potential payoff in reduced usage is already greatly diminished.
At the risk of being heretical, it seems possible to me that the juice isn't worth the squeeze for someone in your situation (though only you can be the judge). Even if you decided to keep the fireplace, rather than replace it with a rocket stove, you could probably do quite a bit to improve both combustion and heating efficiency of the fireplace (though it will still be a fireplace, of
course). For example, you could Rumford-ize it, you could add an operable chimney-top damper and insulate the exterior of the chimney (keeping more of the thermal mass within the heated envelope), you could add glass fireplace doors to improve combustion efficiency by limiting the excess air, add a circulator/Heatilator insert, etc.
As a counterpoint, my own objectives for a solid fuel heater include having a heat source independent of the grid, capable of handling primary heating loads (maintain some livable heated space, even parts of the house get cold), provide comfort and ambiance when used as auxiliary heat, do no violence to the architecture of our house, which was built in stages between about 1890 and 1920, and has a lot of the original casework and leaded glass still intact. In the longer term, these needs may be answered by a batch rocket or a contraflow thermal mass heater (I'm still noodling), but in the near term, I plan to install a fabricated chimney and a soapstone stove (still a thermal mass stove, just very low mass in comparison to a true masonry heater) with good combustion efficiency. Whatever I do in the longer term, it needs to have an aesthetic which is consonant with the architecture of the house.
SO, my best advice is to make a list of all of the things you must have or would like to have in "a place for fire". Note which of those are met by your current fireplace, could be met be adapting or improving your existing fireplace,and compare/contrast with which objectives could be mat by a rocket stove (of one flavor or another). Intangible objectives as you've expressed are still objectives. It doesn't sound like you need to make the decision in haste, so maybe give the subject some thought throughout this heating season, paying careful attention to how and how often and under what circumstances you use your existing fireplace, and whether, as a thought experiment, those uses would be better met by a rocket (J-tube? batch box?) stove.
On edit: I thought maybe I should mention that it is certainly possible to have both an open fireplace and something very like a batch box within the same thermal mass. I hesitate to invoke Igor Kuznetsov's name yet again, lest people take me for a complete fan boy. However, he does have a lot of information freely available, with a good bit of commentary in English (rather than his
native Russian), mostly translated by Alex Chernov (a Canadian member of the Masonry Heater Association), and a bunch of free stove plans. Igor was heavily influenced by Podgorodnikov, who was in turn a student of Grum-Grzhimailo, the first (as far as I am aware) to enunciate the theory of bells by analogizing to inverted ponds. So all that being said, Kuznetsov has several thermal mass heater designs on his website which have both an open fireplace and a more conventional thermal mass heater firebox within the same mass. At least one also has a heated bench. He gives several arrangements with the stove portion either to the side or back to back with the open fireplace, or even to the side, but with the firebox and
ash doors facing the same direction as the fireplace.
Try the "OIK K" plans here (OIK means a heating appliance, K means "kamina" = fireplace):
http://eng.stove.ru/products/oik_k
Especially, maybe see OIK K2 or K3 (back to back), the K1L (with the bench), and the PK1 (firebox door facing the same way as the fireplace) to get an idea of what is possible. Poking around his other plans will show you what else can be done (e.g. the RTIK 6 sun. doesn't have a water jacket, as drawn, but does have a black bake oven and iron cook top plate, and also a heated bench - and the traditional arrangement would be to have a wooden framed bunk bed built at the height of the top of the thermal mass, and perhaps another beneath the bunk with a curtained and paneled enclosure to help retain heat; usually the young, old or sick would have first dibs on the heated upper bunk).
With a bit of work, the standard firebox/ash drawer arrangement shown by Igor could be replaced by a batch box. I have an evil scheme to do just this for an OIK-14 (i.e. strictly space heating)...
There are many other Eastern European and West Asian masonry heater designers and builders, but Igor's stuff is quite accessible (thanks to Alex) for those not speaking Russian, and he is well known and respected (though some seem to have had personality clashes with him, and I can't be the judge of any of that). Igor is quite opinionated about the designs of other stove builders, and sometimes his elbows are a little sharp, so some of this friction may simply be due to his frank assessments of the perceived shortcomings of those other designs cutting a bit close to the bone. He really has very little good to say about most of the state sponsored designs of the late Soviet period, though he does mention that Podgrodnikov's 77cm X 77cm (
footprint) heating stove is "very good". For a flavor of his design philosophy - and his certitude of rectitude! - see: "http://eng.stove.ru/stati/osnovyi_konstruirovaniya_pechey".
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