In my limited experience they do very nicely under coppice since they grow back so quickly and can produce a 6 to 8' shoot in one season. They can be very handy for using as garden stakes and such but they don't last very long 2 seasons at the most.
I'd like to hear a little more about your idea to add a cooking plate to the masonry rocket heater. Where do you envision it being located?
I've also been investigating masonry stoves (non-rocket type) but I'm a bit hesitant because rocket stoves with their high combustion temps seem safer to live with. Some masonry stove designs without a riser worry me when I think that they could be giving off CO2 and CO in the living space. In videos when they take them apart the inside bricks are always black from soot which tells me the temps aren't very high and there are a lot of products of incomplete combustion being produced.
I guess another option would be to create a largish stratification chamber beneath the floor to absorb and slowly release heat and to mitigate a possible overheating situation. In a 10 x 12 foot house a 30" x 72" chamber beneath the floor doesn't seem that hard to incorporate into the design. Especially with a tamped earth floor like I plan to have. I may lose some heat to the ground, but a layer of insulating dry sand around the chamber should cut down on that.
Nicole Alderman wrote:I had no idea one could do something like this. Makes me wonder if horsetails could be made into a 'crete. How's your nettlecrete holding up?
I've wondered the same about horsetails. They are rampant in the low areas down by our local river.
A couple of other plants to consider would be flax, an annual but easily cultivated and seed is widely available, and hemp dogbane (Apocynum cannabinum) a perennial common here in the great plains and also easily cultivated. I just happen to have a cup full of dogbane seedpods sitting on top of my dresser.
Jason Broom wrote:I know you were expecting challenges to this design, but aside from the long-term viability of the stainless steel steam tray pan, it looks like you're going "by the book".
That's great. Would you expand on your specific concerns with the SS pan? According to the info I found, 18/8 stainless has quite a high temperature tolerance.
Long and (relatively) narrow masonry heaters have been built for many years, and a properly constructed rocket mass heater is simply a masonry heater made from less expensive, locally sourced products.
I think your plan will work well, provided you insulate the wall very well from the stove, and the stove from the wall, lest you wind up attempting to heat the entire outdoors.
Since there will be a 6-8 inch space between the back of the strat chamber and the glazed and insulated south wall I'm not anticipating any issues. I want the back of the strat chamber to pull double duty as a Trombe half-wall.
thomas rubino wrote:Hi John;
10x12' sure seems small to me but its your tiny house.
Thanks for your response! 120 sqft (actually a small fraction less) is apparently exempt from universal code requirements. My county is not zoned but I would rather build small now, avoiding any Imperial entanglements, and add on later as needed.
Most important) Do you have a copy of the RMH builders guide yet? Readily available on Amazon.
Yes I do. An older version.
To start a drawing might help clarify things some.
I have ... It does help. Fun fact: The front elevation I sketched up bears a small resemblance to the letters in the name "Jill". :) (J tube on the left.)
Ok) 6" feed tube? Did you mean 5.5 x 5.5 by how deep ?
I'll use the standard 1:2:4 ratio, or as close as I can get it, and follow the generic plans I have as closely as I can.
burn tunnels are generally only 10-12" long.
That's good to know.
A 36" riser made with what material ? Ceramic blanket ? Insulated fire brick ? Heavy firebrick?
36" overall from floor to the top of the cook top. This is to locate the cooking surface at standard kitchen height. I'm thinking a riser of rock wool lined firebrick. I may start out with just the firebrick and add the rock wool liner as soon as I can. Ceramic blanket is new to me. I'll have to compare costs.
What is your plan for the transition area ? Below your cook top ?
Steam table pans have a lip so they can hang inside a standard sized opening. This firm rectangular rim should snug up nicely to the firebrick below once inverted and clay-sand mortar should make a good seal between the sides of the pan extending below the red brick structural top. I wonder if nesting two pans together to increase the overall thickness would be advantageous. I'm not wedded to the steam table pans, but it seems like they would serve well as a smallish rectangular channel between the riser and the diversion tube -- like one independent section of a barrel from riser to barrel edge. The 6" depth and 12" width should allow for good flow across the inner surface of the pan, and the outer surface should get plenty hot enough to set cooking pots and skillets on to be heated for cooking. In my mind it should function very similarly to the top of a barrel, just smaller and more rectangular.
The exit to your stratification chamber should be at the lowest point.
I know that's the standard design. I just don't know how I could have the overall width of the stove be basically the width of the tube plus outer structure only, and still be able to have the exit below the entry tube. Since the hot gasses mix and stratify in the chamber rather chaotically, I don't think it would cause any problems to set the exit tube right on top of the entry tube at the bottom of the structure. Maybe extending the entry tube along the bottom of the chamber a foot or two would be enough to avoid any potential problems with the gasses entering and exiting too quickly without filling the entire chamber for effective mass heating.
Your cook surface is going to be glowing hot at times, my 8" J tube can hit 1100F at the barrel top....
You've hit on one of my most serious concerns with this design. My hope was that using a 6" system, making the riser as tall as possible within the overall height dimension, and giving plenty of clearance between the end of the riser and the inverted bottom of the pan would be sufficient to keep from overheating the cook top while still achieving rocket stove temps for complete combustion. Perhaps a removable cover made of thicker, more massive material would keep the pan from burning up when not having heat pulled out for cooking. I've seen barrel stoves with cob covered plates sitting on top of the barrel to avoid overheating the top. I would also need to experiment to see if there would be an effective range of temperatures across the cook top for cooking. You can't be a very good cook if the only setting on your stove is 'incinerate'. I've considered using trivets of various thicknesses to control the amount of heat being transferred to the cooking vessel.
I am also very concerned that a stove like this will quickly overheat such a small space making the tiny house uncomfortably hot. It seems that the three best solutions to overheating would be mass, mass and more mass, so that the heat is absorbed and released slowly over time. Problem is, this runs contrary to the stated goal of taking up as little floor space as possible in a house with such a tiny floor plan. Since the stratification chamber is tall and thin, it could be acceptable to use seasonally temporary additional thermal mass, such as a drum or two of water right up next to the wall. I'll need a water reservoir inside the house anyway as it will be completely off-grid. Might as well let the water serve two purposes.
Yes I have. It's a great design. Much to emulate there. Unfortunately, I don't really have room for a glass range top, and also it appears to take up a minimum of (I'm guessing) 16-20 sqft of floor space for just the stove and wall clearance. I don't know if I can afford to use that much space all in a chunk in the middle of the house. I've also considered a design like the tiny stove with the gothic arch masonary bell on the top, but I don't know how I would cook on it. I'd rather have a design I can cook on during the cold part of the year and extend the thermal mass along the periphery of the floor plan to take up as little of the most valuable estate as possible.
So I'm designing a 10' by 12' tiny house. My idea is to install a long, narrow J tube rocket mass heater with cooktop along the south wall of the house, with the back surface of the stratification chamber also functioning as a Trombe half-wall.
To minimize space the design needs to have the smallest possible footprint and still function effectively as a mass heater and cookstove. I believe a linear design, long narrow and tall could be the most space efficient.
I'm envisioning a linear design something like this:
1. Beginning on the right side with a 6" feed tube,
2. A burn chamber no longer than absolutely necessary,
3. Then rising a total of 36" from floor height,
4. Into an inverted 6"x 12"x 21" 22 guage stainless steel steam tray pan in place of a barrel to serve as a heating and cooking surface,
5. Then falling to near ground level to empty into a tall, narrow stratification chamber about 48" high and as long as the house will allow.
6. The exhaust would vent just above the chamber entry port and pass as closely as possible to the riser before exiting the house.
7. The whole structure should be as narrow as possible, 15" ideally to 18" if necessary.
8. Standard J tube masonry construction with a rock wool insulated fire brick core and red brick otherwise, with clay sand mortar where appropriate and standard mortar otherwise.
Ok do your duty and pick this idea apart. Cry havoc and let slip the dogs of war.
I live next to the mighty Missouri river and there is tons of native equisetum in ditches and low areas nearby. Has anyone tried using horsetails as fiber in cob? The high silica content seems like it would be a great plus for structural as well as high temperature applications.
Fibrous stinging nettles seems like a good fiber source too, as well as flax and hemp.
Apparently another locally common perennial plant is a very good source of high quality fiber - dogbane / indian hemp.
From Wikipedia: A very strong and good quality fiber obtained from the bark is a flax substitute that does not shrink and retains its strength in water. It is used for making clothes, twine and cordage, bags, linen, paper, and more. When harvested for fiber, dogbane is often left standing as late as mid-winter so that rain and snow will perform retting. Apocynum cannabinum was used as a source of fiber by Native Americans to make bows, fire-bows, nets, tie down straps, hunting nets, fishing lines, and clothing.
I'm envisioning ways to generate negative pressure for off grid tiny house or small cabin passive cooling applications such as geothermal and evaporative cooling.
I believe I would need to generate pretty significant negative pressure in order to draw enough air through any passive cooling system regardless of the type.
I've thought of generating air flow using passive solar energy like simple thermal chimneys, utilising the heat that collects in the attic space above the insulated ceiling, and heating air by using a solar collector such as a modified solar cooker design, but I have my doubts that passive solar alone can provide enough air flow for effective cooling.
Years ago an old timer told me how long ago people would use their fireplace to cool their homes by creating negative pressure to draw cooler outside air into the house by heating and displacing air in the chimney.
So that started me thinking ... has anyone ever tried using a rocket stove specically as an air pump?
I know that rocket stoves draw a lot of air. It would be interesting to see what kind of negative pressure could be tolerated behind the air intake without losing too much combustive efficiency.
Undoubtedly the rocket stove would be best located outside the structure with air being drawn from the space being cooled by ductwork. With a significant amount of air resistance resulting from all the ductwork used in the cooling system I wonder if a closed system could sustain combustion at a rate sufficient to produce the pressure required to move air through the cooling system to result in effective cooling.
The rocket stove wouldn't even necessarily need to be used continually. It could be used in conjunction with passive solar heating to rapidly get air circulating during system startup, and also on days when the temperature is still very warm but there isn't enough consistent sunshine to maximize passive solar energy.
Miles Flansburg wrote:Much better! It looks like there might even be variations from person to person, home to home ?
Certainly. There are features common in certain villages more than others, depending on the builders' experience, training and preferences.
These houses require more labor and materials than just a simple, typical African roundhouse, so people with limited resources tend to live in houses with the simpler design. If you notice from the videos I posted, having this kind of traditional house seems to be a status symbol so they must be relatively quite a bit more expensive to build and maintain. Wealthier people also tend to build homes influenced by Western homes, with rectangular floor plans, multiple attached rooms, porches, and corrugated sheet metal roofs.
Seems like this might work anywhere that it is hot and rainy.
I agree. I was wondering what, if any, adaptations would need to be made for a more temperate climate, with a cold winter as well as a hot summer. Perhaps a way to close off the high ceiling in the central area would be helpful during the cold season. A range of ceiling joists could be installed at about eight or nine feet high, with woven mats or some other lightweight ceiling material laid across them to hold heated air closer to the living space. Insulation could be placed over the top for more heat retention. Then, as the warm season approaches, these mats could be rolled up or removed to take advantage of the high ceiling's ability to allow heat to rise and escape the structure.
I owned a Tipi for years and there are similarities. Opening at ground level, inside liner or wall, creates a draft that cools the room. Cone shape. Neat
This design would be almost like a tipi within a tipi, wouldn't it? A Hypertipi!
That reminds me of a video I once saw where there was a covered, tent-like structure surrounding a bed raised up off the ground, all within a yurt or a larger tent. Apparently it was quite warm in the bed just from body heat alone, even when the outside temperature was extremely cold.
Stinging nettles are a very good indicator plant for rich, fertile soil. They are also very useful for cordage fiber made by retting the winter killed stems. I agree that they are best kept in your zone 5, or if necessary, in an escape proof bed. In Eastern Kansas, nettles are one of the first perennials to put up shoots in the Spring, and are a welcome source of greens. Shoots 2-3 inches high are the most tender and flavorful in my opinion. They also have very little sting at that size. Just wear a pair of cotton or rubber gloves when picking them. You can extend your harvest by cutting the shoots down to the ground even if you don't need them so that a continual harvest of baby shoots is available for several weeks.
Also, no discussion of nettles would be complete without this ...
Old Mr.B! Riddle-me-ree!
Hitty Pitty within the wall,
Hitty Pitty without the wall;
If you touch Hitty Pitty,
Hitty Pitty will bite you!
I've often thought that bottle gourds would make good plant nursery containers. If kept a little off the ground, hey would probably last long enough for a seedling to become established, then could simply be placed in a garden bed to decompose as the plant grows.
In my younger days I was fortunate enough to have spent two years in West Africa in the Peace Corps. The Republic of Guinea is comprised of several different ethnic and geological regions. While I was stationed in the southern forest zone, I had the opportunity to visit the north-central area known as the Futa Jallon region, home of the Pular people, a branch of the Fulani.
The traditional Pular roundhouse has a design feature I have not seen come up in natural construction discussions, one specific design feature that I think stacks functions in an elegant way.
The basic design of the house consists of two concentric circular earthen walls with a thatched pole roof. The outer circle is about head height while the inner circle is raised significantly higher to support the roof poles at the desired pitch while also defining the central living space.
Most communal functions occur within the central area while doorways through the inner wall provide access to spaces divided by radial walls extending between the inner wall and outer wall. These spaces afford a greater degree of privacy and are used for bedrooms or storage areas. On one side a doorway extends through both walls for egress with radiating walls defining a passageway or vestibule.
The high inner wall allows heat to rise and cooler air to stratify below, a benefit in Guinea's warm climate. Windows are not traditionally a part of the design but the roof is attached in such a way as to leave a gap at the top of the walls to allow ventilation and the entry of diffused light. Ventilation also occurs around loose fitting doors or curtains hung in doorways. Warm air rises and exits through the thatched roof.
The roof is constructed so that it overhangs the structure almost to the ground, protecting the walls from erosion during the rainy season which can see over three meters of rainfall, while also providing a protected area for more storage and shelter for small livestock.
What are some ways this basic design might be adapted for a temperate climate? What are some pros and cons you can see with this design?
Thanks Cindy. That's good information. I'm specifically thinking of construction applications but an RMH is also something I do want to do eventually.
I like your idea about using chopped straw versus long straw. It seems that that would allow for a higher percentage of straw in the mix and therefore more cushioning against shrinking and swelling.
Since I'm new to cob construction I have a question regarding straw also. It seems to me that the straw would break down very quickly and you would lose any binding property in a very short period of time and be left with only a network of elongated pores throughout the mass. Since this apparently is not a problem in real life, I'm wondering if someone could explain it to me.
I currently live among the loess deposits on either side of the Missouri River basin. Has anyone had experience making cob with loess subsoils?
I understand that along the Yangtze River basin houses and other structures are traditionally excavated out of loess soils.
Soon, however, I will be moving to my family farm that has heavy clay soil with high shrink-swell capacity. How well do expansive soils work as the clay component of cob?
Also, there are several old gravel quarries near the farm and there are large piles of old limestone screenings. I know the owner and could probably obtain all I want for cheap or free. How would limestone screens mixed with clay and straw do for cob?
I currently live among the loess deposits on either side of the Missouri River basin. Has anyone had experience making cob with loess subsoils? I understand that along the Yangtze River basin houses and other structures are traditionally excavated out of loess soils.
Tj Jefferson wrote:I got several kilos of osage orange seeds, and am trying them in a thick forest planting. I think like most trees they grow in a rat's nest because they were planted in hedgerows, not having to compete for upper growth. We shall find out in 15 years, when I am planning on replacing the fence. The good thing is that that is bout the life expectancy on my current posts.
I'm planning a hedge of alternating osage orange and honey locust surrounding my food forest, to be laid like a simple English hedge. Hopefully that will keep the deer out and the goats in when it's mature. Both species of tree grow like weeds on the site naturally.
Chris Kott wrote:Which would win, osage orange or black locust?
Black locust unless you want to live in a nest.
I don't understand about the nest.
I've actually seen these side by side. Black locust is a much softer wood, and even with naturally rot resistant wood they only seem to last 10 to 20 years. Whereas when you make fence with hedge posts you have to use special short staples because you just can't drive them in very far. There are osage orange corner posts on my dad's farm that were very old when he purchased the property in 1970 that are still very solid and firmly supported in the ground. Even 3 to 4 inch hedge posts are known to last 50 to 75 years
There are some very old clay pipes lying around my family farm. There are 4" inside with 6" flange, and there is a 36" piece, a 90 degree piece and a 12" x 36" catcher with a 4" connector at the bottom.
Would these stand up to the heat that a rocket stove makes? Seems like if so they would make good stove components.
It looks like there is a technology in development that uses passive solar energy to circulate water in a pond for aeration. I found this thesis on pdf after a bit of googling for "passive solar fish pond aeration".
Spoiler alert: The best design used an inverted prism-shaped structure made of sheet metal covered in glazing at the top with buoys providing the necessary flotation ability. Even this design was only minimally effective, though, and further research and development is needed.
Composting tower concept
I had an idea about a composting system last night. I have never heard of anything like it before but someone very well could have this thing sitting in their back yard already for all I know.
The concept is similar to a composting system I've seen that uses four compost piles laid out on the ground which are eventually consolidated into two, then into one pile of finished compost. Typically, a great deal of strenuous labor is involved in first creating the four piles, turning the piles, and then consolidating them in order to have sufficient mass for efficient composting.
The significant change would be to arrange the compost piles in bins or boxes vertically on a frame in order to use gravity for transferring, aerating and mixing the composting materials.
The structure would consist of a frame of wood or steel, seven large boxes or bins, and hinges and latches for trap doors on the bottom of six of the bins.
The system would begin with four horizontal primary bins at the top of a tower frame where they could be fairly easily loaded with lightweight brown and green material, either using a ladder and baskets (and a couple of helpers!) or a simple conveyor system. You get extra energy points if you are lucky enough to have a steep slope to build the structure on, so that you to have the top bins at or near ground level at the top.
When the material has composted down to half the original volume, side-hinged trap doors on the bottom of the bins could be opened to allow the composting material to simply fall into to the next level of two secondary bins. Trap doors hinged in pair of opposite sides would act as a funnel, directing flow of two upper bins into one lower bin. The doors would be fastened with pins that could be knocked out with a hammer while the door is bearing the weight of the compost. Side fins on the trap doors would reduce spillage. The composting material would be mixed and aerated during the gravity transfer.
When the contents of the secondary bins have reduced in volume by half again, the almost finished compost would be dropped to the single bottom bin where it would eventually be available for easy access.
An option to raise the whole thing up even higher to allow gravity feeding of the finished compost into a wheelbarrow or trailer through a chute below the bottom bin would make this thing darn near perfect.
Benefits of this system include having the most labor intensive portion of the process involved in lifting the lightest components. Gravity is used to transfer, mix and aerate the material as it moves through the composting process. The process could be continuous with material in different stages of composting present in all three levels at one time.
Problems to overcome would include the cost and construction of the frame, the work involved in lifting materials to the top bins, keeping the top bins moist enough in hot weather, and possible spillage.
Hugo Morvan wrote:I haven't seen it from upclose, so can't really say if it's safe. I take it it's not in danger of immediate collapse. Ask a professional.
Thankfully I'll have a brother-in-law and nephew nearby who are both pretty knowledgeable.
Where i to fix it i'd seal the cracks with a cement/sand mix, first from the inside, so make it thick and sticky. Wait for it to harden and fill it from above with a sloppy mix. Push it in with a small stick.Fill it completely. Wait a day for it to harden. That will keep the water from coming in and worsening the problem. Then phase 2 bang the loose render of the wall with a hammer and render the walls. Phase 3 lock on the door so kids can't come in. Phase 4 keep a close eye on the repaired bits, if cracks don't open i wouldn't worry too much about it being unstable.
If you're unfamiliar with what i'm saying call in a expert to do the job.
Sounds like solid advice. Thanks! One downside of the old home place is tight clay soil with a high shrink–swell capacity. Over time it can beat up underground structures pretty viscously. This is probably a 1940s era structure. There are also two remaining underground cisterns that I need to check to see if they will hold water.
I will be returning to live on my family farm soon. While walking the property last weekend I was saddened to find the state of the root cellar to be much worse than I had hoped. (See images below)
I would appreciate any advice I can get regarding repairs or if repairs are even feasible at this point. Safety would be my major concern since I will have my children there with me and I'm sure they will be playing on it often just like I did as a child.