Opinions Needed: BBRMH viable for large shop area?

First time posting so a brief bit about us... we have been living the good life, homesteading off-grid for the past 7 years in the beautiful Sangre de Cristo Mountains of Colorado. We try to be as efficient and self sufficient as we can. Following is the situation and question at hand...

We have a 42’ x 48’ shop with 14’ ceiling height (~28,000 cu ft), insulated pole barn construction, with a common wall to our 800 sq ft house. We currently run a Jotul F50 wood stove and an antique wood/coal cook stove (fun to look at but horribly inefficient) in the shop for heat. We can maintain 60 degrees through the winter with just morning burns or all day when its single digits or teens during the day. We are burning about 6-7 cords a year just for the shop. It rarely ever dips below 50 in the shop in the morning before lighting the stoves, so we look to increase the temperature with our wood-burning appliances by about 10-15 degrees. It would be great to reduce our annual demand for wood and be a lot more efficient with what we do burn. Also, we have 70 acres with lots of Gamble oak, so lots of small diameter hardwood to feed a RMH.

We are really intrigued with the BBRMH concept and would consider taking out the old cook stove to use the chimney from that. Before I get too excited to invest lots of time researching we are hoping to get some comments from you experts if it is even a reasonable approach given the size of the area to be heated. I’m not afraid of investing the time to research and learn but if this is not a viable option for this size space I have enough to do everyday with the greenhouse and general homestead operations. Thanks in advance for any and all input.

Hi Glenn;
A batchbox stove with a brick bell would reduce your firewood requirements.
My shop is much smaller at 24x32 with 16' ceilings it is only partially insulated on the walls.
My 7" double barrel batch does an outstanding job of quickly raising the temperature, thanks to the double barrels.
The brick bell easily stays warm all night even with no ceiling insulation and the large uninsulated door with gaps you can see through.
In northern Montana, when I burn during the day it is still 40F across the room the next morning.
Your shop sounds much tighter.

Hi Glenn, there is no doubt that a similar size, well built rocket stove with a heat storing mass, will out perform you existing stove!
However these  things can be time consuming to build and quite expensive depending on what you have available on site or can find locally.  
So a lot will depend on your budget and time scale?
Rocket mass heaters can be made to look very neat and tidy, perhaps for inside a living space, or very basic but, functional for a work space or, of course, if looks are of no concern it will be cheaper and faster to build n matter where it lives!
A big batch box with twin barrels might not look very nice in a living space but, boy it will throw out some heat!

Some questions: is the shop in use all and every day? And what type of work is done in there?

To clarify, a shop that is in use every day can be kept at a certain base temperature with a large masonry bell. So the heater could be fired up once or twice a day. This heater need to be large and heavy, at least 3.3 US tons. Placement preferably centrally in the space but it could do with a placement along one of the walls, provided insulation of the shop is adequate.

On the other hand, in case the space isn't occupied all and every day, it's better to have a quick heater that heats up very fast. And of course, it will emit lots of hot air in stark contrast with the masonry variant. In my own former workshop I used a small coal heater burning wood mainly, later on I built a heavy masonry heater which reacted very slow.

But: the shop wasn't in use during part of the week so I started every time at a very low temperature and a cold heater. Later on, during development of the batchrocket core, I fabricated a three barrel tower. Which in contrast wasn't heavy at all and emitted heat very quick. This happened to be the best heater for my use of the workshop. The shop was about 37.5' long, 18' wide and 10' high, uninsulated although between two other inhabited buildings, walls all brickwork, large doors front and rear which were very old and drafty. In the depth of our mild winters the temperature dropped to 44 ºF inside.

It didn't really matter what the temperature was to begin with, running the barrel tower caused the shop's temperature to rise within 10 minutes.

So, main question: is the shop in use all week or not?

First I’ll just say WOW! I’ve had some wonderful experiences with great forum communities on other topics and I can see with just a few responses that you guys help to define a great community… thank you for your replies so far!

At a high level it appears that a properly designed stove could provide the desired results. Some comments for each of you:

@thomas-rubino - Thanks for the description of your shop and heater. Regarding our shop, it is quite tight for a pole barn building and 2 of the 4 walls are partially below grade which also helps.

@fox-james - we have not determined our budget for this yet as we are in the initial information gathering stage. We are by no means wealthy but we try to approach our budget for projects with the idea of “do it right” and “buy once - cry once”. We have a budget for homestead improvements and we will enjoy a long term reduction in cost and labor for wood collection with a more efficient setup. I retired from corporate America this year so homestead projects and daily chores are my sole focus now. We’re excited to dive into the learning experience.

@Peter-van den berg - our entire homestead has been an evolution over the past 7 years. We started out living in our motorhome while we build. When the building shell was dried in it was October and winter moved in here so we lived in the shop in the motorhome occupying about half of the space and the other half was wood shop, tile works, and general work area while we built the house. Since then we have continued to evolve the space and built a separate garage building so the shop area has continually shrunk replaced by living space, an indoor grow room for starting veggies for the greenhouse and a grow area for lettuce beds and herbs. The shop now features a comfy seating area, a dining room table, bar, a food processing area, and a bunkhouse for guests to stay. The house is only 800 sq ft so we live in the shop area as much as we are in the house, so long answer to your question… yes, we are in the shop everyday throughout the day. Having a heat source that has sufficient thermal mass to retain heat through the night would be awesome.

I’ve had a chance to just begin looking at DragonTech and Batchrocket websites. Time is a bit short this week as we are hunting deer and elk along with our regular chores but starting next week winter is here and education time begins. If you guys, or anyone else, have recommendations for learning resources (websites, videos, books, etc) that would be great. I would prefer not to bombard the forum with questions until I have a good understanding of the technology and can at least ask questions that haven’t already been answered 1,000 times.

Thank you all again! Looking forward to the journey.

Hi Glenn,

Welcome to Permi3s.

Glenn Littman wrote:The shop now features a comfy seating area, a dining room table, bar, a food processing area, and a bunkhouse for guests to stay. The house is only 800 sq ft so we live in the shop area as much as we are in the house, so long answer to your question… yes, we are in the shop everyday throughout the day. Having a heat source that has sufficient thermal mass to retain heat through the night would be awesome.

That's settled then, a pure mass heater looks like being the way to go. An 8" batchrocket housed inside a large brick bell, maybe even a completely double skinned one so it will be capable to stay warm for over 24 hours when need be. Since you are sort of living in the shop, maybe even a bell bench? The upshot is, that your firewood requirement for the shop will be halved, at least.
You'll need quite some ordinary bricks, full firebricks and probably also split firebricks, some steel T-profiles and ceramic blanket, preferably Morgan thermal ceramics superwool.

Is there a space available that's centered in the shop? As placement, that would be best. You *could* choose to use it as an open system, without a door. Or, ask Thomas to fabricate a plunge door. That door doesn't have hinges and a door frame, it is mounted at an angle, so it leans naturally to the core. There's an example how this is done, see https://permies.com/t/193821/inch-batch-box-rocket-mass
More cutting of bricks is involved, but less or no welding and so on.

Peter van den Berg wrote:That's settled then, a pure mass heater looks like being the way to go. An 8" batchrocket housed inside a large brick bell, maybe even a completely double skinned one so it will be capable to stay warm for over 24 hours when need be.

Is there a space available that's centered in the shop? As placement, that would be best.

Awesome, great to know that this is a viable pursuit to improve our heating and efficiency. I'm so early on in the education process that I don't yet know what I don't know. I'll be reading everything on your website as soon as the server is back online. Also, looking for more resources to learn as much as I can before moving to the next step of design and materials acquisition.

As for space, we can center it in the shop toward one end that is closest to the overhead doors since that is the coldest part of the shop and the antique cook stove and chimney stove pipe are already located there.

Two questions
- The stove pipe is 6" single wall up to the point that it reaches the metal drop ceiling, then it changes to an insulated double wall pipe. Will the 6" stove pipe dictate (limit) the size of the heater or will is be sufficient for the 8" batchrocket that you suggest?
- We live at 8,000' (2,400+ meters) ASL, will this have any bearing on the design to allow for less oxygen or air density?

Glenn Littman wrote:Two questions
- The stove pipe is 6" single wall up to the point that it reaches the metal drop ceiling, then it changes to an insulated double wall pipe. Will the 6" stove pipe dictate (limit) the size of the heater or will is be sufficient for the 8" batchrocket that you suggest?

Hate to disappoint you, but no. One size larger would be OK, smaller won't. It's a pity, one bigger system, 8", 9", should be capable to warm the whole of the shop. So with the existing chimney you're tied to a 6" batchrocket. Is the other chimney also a 6"? Maybe twin heaters?

Glenn Littman wrote: - We live at 8,000' (2,400+ meters) ASL, will this have any bearing on the design to allow for less oxygen or air density?

Everywhere on earth the oxygen content in air is 21%, density is the factor to be reckoned with. In my experience, the air inlet should be somewhat larger, don't not for sure how much though.

Peter van den Berg wrote:Hate to disappoint you, but no. One size larger would be OK, smaller won't. It's a pity, one bigger system, 8", 9", should be capable to warm the whole of the shop. So with the existing chimney you're tied to a 6" batchrocket. Is the other chimney also a 6"? Maybe twin heaters?

Thanks Peter... good to get the basic design requirements understood early on. My Jotul stove also has a 6" chimney. My immediate thought is to build a 6" batchrocket to replace the old cook stove. Get the benefit of "lessons learned" from that and then tackle replacing the Jotul and incorporate a bench into the design since I have a seating area at the Jotul now.

Peter van den Berg wrote:In my experience, the air inlet should be somewhat larger, don't not for sure how much though.

I assumed that would be the case. I had to re-jet the carburator on my old Ford pickup truck with a smaller jet to get the right air/fuel mixture. Perhaps if there are others on the forum with high elevation experience they will comment.