Glenn Littman

Magnificent job Cedric. Great job at documenting the build too. Enjoy your radiant warmth!

Your build really illustrates the benefit of a shorty core allowing you to place the firebox high in the bell. Easy & comfortable loading and lighting. Love the plaster exterior so it blends perfectly with the rest of the room. Just magnificent!

Rico Loma wrote:Jeff, your post is on target.
Sure, we all have a choice to lie to a home insurance agent.  Some folks think that's a good game to play, but I can't do that. Financial suicide, in my opinion. Of course I believe an RMH is safer and better. However, my agent sticks with the company policy, and no discussion with me.

I guess different areas have different approaches with writing insurance policies. I probably change insurance companies every 2 years so I can play their rate increase game and keep my premiums as low as possible. I have never had an insurance agent ask if I have any wood burners in the home or even anything about how I am heating my house. So, I've never made any deceptive statements about my property and to be very clear am not I recommending that anyone do so. If insurability of your home by adding an RMH is a concern than I'm all for reducing stress and just shelve the idea and find some other fun projects to pursue.

Magnificent Peter! Congrats on your efforts and creating another masterpiece. Has it been named yet? I'll toss out a few thoughts that come to mind... Godzilla or perhaps Gargantua.

I didn't see any mention in your build commentary... did you embed any thermocouples in the mass? It would be quite interesting to see what the inside skin temps are running. I actually find that monitoring my inside skin temps helps me to manage the external skin temps better as it will give an advanced idea of system temperature profile.

Once the system is fully dry it will be interesting to know the firing cycles to get it up to temperature and maintain it considering the enormous mass. It will also be interesting to see how it retains the heat over the 35-40 hours that the store is closed and the external temperature when they reopen on Monday.

Mark Reed wrote:I'm still a bit confused, what is a batchbox?

Mark, here is a batch box filled with wood. As you can see you don't use large logs and you fill the box fully. In this case, this is a follow-up 2nd burn with coals in the bottom that ignite the wood. Easy peasy...

Jeff Marchand wrote:Glen, I think its extremely unwise to have a heat source in your home that insurance has not signed off on regardless of whether your home is new or an existing build.

I respect your opinion Jeff and happy that you shared it. This really comes down to a personal choice. We are hyper focused on safety since we live hours away from the nearest hospital and emergency services in our area have a response time that is marginal at best. Regardless, our risk/reward assessment for our way of life highly favors the many benefits of a batch box RMH. For the population of folks who have a similar approach it is a fantastic way to heat. For those who see the risk as too high they should stick with whatever helps them feel safe.

Mark Reed wrote:I'm still a bit confused, what is a batchbox?

Great question Mark. It is so easy for those who understand the terminology to just assume everyone is on the same page. The pictures will help to tell the story if you scroll up a few posts to the one from Thomas Rubino. He is showing both J-tube and batchbox versions of rocket mass heaters. The J-tube design has an open vertical wood feed tube that you place a few pieces of wood into the tube vertically and and the wood essentially burns from the bottom and drops into the tube as it burns. The batchbox utilizes a larger combustion chamber which you load a "batch" of wood filling the "box" (combustion chamber) and it burns the entire batch requiring no feeding or need to continuously tend. If I can find a picture of mine with a batch ready to fire up I'll post it to help tell the story. As Thomas mentioned in his post above, the J-tube will need your participation to continually feed it since the wood load is pretty small per burn whereas the batchbox can take a good load of wood, the door is closed and you can go about your business. There are further differences in the way that a batch box performs versus a j-tube but I'll stop there and wait for any follow-up questions. I hope this helps to answer your question.

A quick thanks to all who have participated so far on this thread. Sharing ideas, questions and concerns is what makes a public forum valuable.

It appears that the single biggest reason that contributors have mentioned as to the reason for not building an RMH is the concern for uninsurability of their home. For a new home build this becomes more of an issue when a building permit is closed and the local county creates the home profile for real estate tax purposes indicating that the primary heat source for the home is a wood stove. If this is the case for concern, when planning the build, having another source of heat that can be viewed by the local authorities and insurance companies as the primary heat source would get around this. It also provides a means of keeping the pipes from freezing if you will be away from home for multiple days. For existing construction with a different primary heat source, this is much less of an issue. I’ve never experienced an insurance company demanding to walk-through my home to see what is going on inside. So, this really becomes personal choice whether or not to allow a potential concern to drive your decision-making of what you do in your home. I can tell you that going on my 3rd heating season with my batch box design RMH (assuming the person follows the build design that many of us have adopted for a double-skin RHM with the guidance provided for a “proven design” as Peter van den Berg would say) a batch box RMH is safer than any metal box stove and as safe if not safer than any standard method of heating a home. Of course, this decision is one for each person to make, I’m not trying to tell you what to do.

It would appear that the next biggest reason is perhaps confusion over the various designs and their benefits/challenges in being able to compare them, leading to avoidance to proceed. My observation over the past few years of researching then building my own batch box is that you have to really invest time to read Permies Donkeys (Proboards) forum and any other resource you can find, and most importantly, ask lots of questions there are lots of great people ready to help you get started. Unfortunately, there is no single, easily accessible source that fully walks a newbie through the technology options, general nomenclature used, the benefits and use-cases of each and a general guide to building. So, the profile of a successful RMH builder is someone who is unafraid to tackle a somewhat complex project and construction skills that they may not currently possess.

Other reasons were also mentioned, including the existing home structure being insufficient to support the weight of a RMH and no reasonable alternate place to locate, like a basement. My goal with this thread is simply to get people talking to perhaps spark interest and ideas to incorporate this wonderful old world means of wood heat but doing so in a much more efficient manner. Keep the conversation going!

tony uljee wrote:the way i am reading it ,is the shop floor is 30 meters square ---not 30m2 ----so its 30 m x 30m equates to 900m2   which is 9690 sq ft  

Thank you for the clarification Tony. That makes more sense than the way I read it. That also makes sense now with that large of an area and to sizing the system to 200 mm.

Bravo Peter... another PvdB masterpiece in the making.

I really like the idea of the clinkers and then plastering over them. Also, love the firebox height, courtesy of the shorty core. I made mine as high as I could without making the total height too crazy due to the original core/riser design. The Shorty is a huge benefit in this regard.

My mass is similar to Tom's. Mine calculates to a bit under your designed, with mine coming in at 3.5 tons and will hold a skin temperature of 135 to 150F which makes a significant impact for the large space that we are heating. With over 4 tons of mass your customer will undoubtedly love it when its up and running. I think your store space calculation conversion to sq ft is incorrect. 30 sq meters = 322 sq ft. Considering this size space the heater perhaps they will be able to eliminate the gas heat all together.

Isn't it time to update this Wiki to include education about the various Batch Box designs which may be preferred by many folks looking to consider building their own heater?