Brick build J style rocket mass heaters question

HI,

A wee bit about me, I joined the forum / webstie a couple years ago, but found that when I came here, I did not know how to navigate this site, my head would / does spin, not knowing what to do. I still have the same problem. The fact that It took me so long to find this topic and then to struggle to find how to make a topic, says that I am  struggling with understanding. But I got here, and grateful for that miracle.  Nothing against this place, I think the topics are fabulous, its me.

Now to the point, over time, and tid bits gathered mainly from emails from this place, that if one wants to build a rocket mass heater, and I do want to build one.  That its best to do it with brick and to have it    "  J   " styled.

Back to the limits of my understanding.

Is there, some resource material, - a book that anyone knows of  on how to build :  a  " J " styled brick rocket mass heater, that is designed for people like me, who needs their hand held and every single step shown, preferably with pictures,  and each step explained ? Even an electronic online book could work, I could print it.

Any help would be greatly appreciated !

Cheers

Joy

Hi Joy.
There’s a very good wiki on this site that lists a lot of resources, including 2 books.

https://permies.com/w/rmh-resources

Hope this helps.

Hi Joy;
Welcome to Permies!
You did a fine job with your first post, it will get easier now that you have started.

Currently, the Rocket Mass Heater  Builders Guide by Ernie & Erica Wisner is the most complete book on J-Tube rocket construction.
It's a fabulous book, but it might be more complex than you are hoping for.
I have it in my head to write just the book you are looking for but I have not yet found the time!
Writing the RMH batchbox build book and door construction manual took me forever.

The whole process is simple but very intimidating for a newbie.
The part that you and all new builders, have the most trouble grasping is the "transition" area.
This is where the heat from your riser (inner chimney) changes direction and travels downward into the mass.

We will gladly help to guide you during the learning curve.

The Wisners' book is, as Thomas mentioned, perhaps more comprehensive than you want for your direct needs, but if you can help us narrow your focus, we can probably recommend one build from their book that you can follow. They do give complete layer-by-layer plans for many of the designs.

What is your climate, and your house size and construction? Where in the house are you thinking of putting a RMH? What are the dimensions and clearances of that area? What existing or potential chimney resources do you have?

Benjamin Dinkel - thank you for that link it has some amazing topics there.


Thomas Rubino - thank you! and if you ever write that book, I will be the first  in line for it!
What is your link to your:   RMH batchbox build book ?
Thank you for explaining  that a  riser  is an inner chimney.
One term of understanding, and how many to go?  chuckles.


Glenn Herbert -  thank you. You ask a lot of good questions.
What is your climate : Ontario Canada - Can be very cold winters.
and your house size and construction:   main floor is about 1000 sq feet and the loft is about 600 sq feet. Wood  frame.
Where in the house are you thinking of putting a RMH? I was thinking the main floor might be best.
What are the dimensions and clearances of that area?  I can be flexable in length of it - its open concept,  the clearance is eight feet tall
What existing or potential chimney resources do you have? there are no existing chimney resources.

Hi Joy;
Here is a link to my RMH store.   https://dragontechrmh.com/
The books in digital or hard copy are available there.
With your location, the size of your home, and the open layout, I would look at building a 6" Batchbox with a brick stratification chamber (bell).
Batchboxes are more work to build, but the longevity of the fire along with the convenience of horizontal wood and a fully closing door make them a serious contender.
A person could start with a J-Tube RMH into a bell and then upgrade in a year or two to a Batchbox as you become more familiar with the newest innovations and their possibility's

Here is a link to my changeover from J-Tube to a Batchbox.
https://permies.com/t/148226/Dragon-Transformation-tube-Batch-Box


 

Thank you Thomas.



I did find  the book written by the Wisners, and was about to order it.  Then I mentioned it to a family member on the phone, and well, that conversation did not go to well.
I was told that the reason you don't find anyone who owns a rocket mass heater in life, not on the internet, is that they don't work.  Frankly, I am confused, and some head spinning.

This is some of  what I was told, that physics means that heat can not go down. This family member knew of the rocket mass heaters and the structure of them, which totally surprised me.  He said that yes, the wood goes in vertical, and the fire's warmth goes up, but it can not go down, into a thermal mass of say a  clay built couch.  He said it condenses as it cools and they you  have pipes with creosole in it.  My head is spinning.

Some advice please,
I love the idea of these, and when there is no power, you have heat and can cook. Besides that, what I like about these, is that you don't have to cut down a forest to heat your home.


Also part of why I mentioned it to my family member is that I found some fire brick on sale, and thought I would get some towards building the rocket mass heater next year.
P.S
I assume I need some fire brick, can you please advise on this, and how much / many?

I would also like to say,  I am so grateful that I was able to post and extra grateful to those who  have replied.

Ha Joy;
First off, buy the firebricks, if the price is right.
How many??? all they have... or at least 30-40 if they have them.
After that, you might want solid clay bricks if they are around.

Your relatives mean well, some of what they told you is true and some is not.
Everyone is entitled to their own opinion.

My home has four working RMHs, I just removed the last wood gobbler stove a few weeks ago.
Currently, temps are cool but not cold, around freezing at night and 40s-50s during the day.
I am only lighting one fire a day, it lasts a couple of hours, and then no fire at all till the next day.
We have been leaving the bedroom window open all night to cool things off!
During real winter (N. Montana) I expect to burn 2 or 3 times a day... that's it.
The stove I removed after 35 years would be lit by now and would not go out for more than a couple of hours until May or June depending on the year.

Here is a link to my new RMH Shorty Core  https://permies.com/t/267527/Shorty-Core-bell

Sorry, but your family member does not know enough about RMHs to understand how they actually work. Two major reasons you don't see RMHs all over are that they are generally a DIY fixture and people willing and able to take on a project like this are not common; and being rare, insurance companies and building code officials often are unfamiliar with them and so afraid of them. A big point to remember if you need to talk to insurance companies or officials is to never say "rocket mass heater", but refer to your "masonry heater". Those are still rare, but have centuries of European history behind them and a building code chapter that covers them.

In a J-tube, the wood does stand vertically with the draft rushing down around it, then the fire goes horizontally for a short way and turns vertical to complete its combustion. The riser gives a big push to the draft as the fire rises, and when it reaches the top, the fire is finished, there is no more combustible gas to burn, and the exhaust gases fall down as they cool. The original style with ducts in a mass bench gives its heat to the mass around the duct. The more recent style called a "bell" features a hollow masonry box with the combustion core inside it. The hottest gases rise to the top, give up heat to the box, and fall as they cool, until only the coolest gases exit the bell from the bottom to the chimney.

Hot air or water rises, but radiant heat goes in all directions equally. The super-hot gases at the top of the riser cool and become denser as they drop, whether to bench ducts or in a bell.
The RMH core design burns every bit of combustible gas including the creosote, so there is no creosote to condense.

You will want firebricks, from a few dozen to a couple hundred depending on what exactly you build. If you find a really good sale, you might want to buy all you can afford in that range.

For your particular house, it does sound like a 6" batch box with a bell would work very well. If you want to start with an 8" J-tube, my experience is that a well-drafting 6" metal chimney will still work fine. The hot gases in the 8" core will be much, much cooler, denser, and take up less space as they move through the chimney, so I find there is not a bottleneck. If you later build a 6" batch box, your chimney will be sized right. (Experience indicates that the output of an 8" J-tube and a 6" batch box are similar.) With a loft and some two-story space, I think a vertical bell (taller than wide) on the main floor would be ideal. About 3' x 3' x 6' is a possible rough outline. If you want a warm bench too, that can be part of the bell system. What sort of basement do you have? One thing about a tall bell is that it concentrates the load, so will require actual footings, while a low bench can often be spread out over many floor joists and not require any extra footings.

Thomas,  wow, I followed your link and that is amazing work!

I am making arrangements to get the firebricks, they are a good price.

Do you know how many firebricks you used in building shorty?

Thank you for your kind words and understanding.



Glenn,  thank  you for your kind words and your understanding.
I really appreciate how you explained what  you did.
There is no basement, its a cement pad.

Hi Joy;
Thank you!
Shorty's core used apx. 45 firebricks and the floor stand used at least 12 more.
There are three large slabs that need to be hand cast as well.
There are also 12 split firebricks as the low roof over her.
There are 6 Firebricks at the top of the core to protect the front wall.

Apx 450 solid clay bricks