Rocket Mass Stoves for Cooking & Home Heat

Rocket stoves are renowned for their clean burn and low fuel consumption and have a abundance of practical uses. Applying this technology to larger mass heaters conserves firewood and expands the stove’s range to serve a homestead or farm well. Living Web Farm's Energy and Resource Coordinator, Richard Freudenberger, will show how us how to build a basic rocket heater using common and salvaged materials and how to apply the same fundamental principals to a variety of designs. We will work through planning, site prep, theory, function and construction of an 8-inch rocket mass heater at our North Mills River farm. In part 1, we begin by building a 9 by 5 foot cob and stone mass heater.

[@Aikidoman06]

Great video! I bought a house in the country with a large steel (65x50) workshop. It had a cast iron stove for heat. We tore it out and built a rocket mass stove/heater. It’s between two rollup doors and will heat the shop so well. There’s an overhead fan that moves air around. Best invention ever

[@alanschaller5869]

Cleaver how they used two barrels do you can easily replaced the spent burn barrel...

[@jakebredthauer5100]

@@alanschaller5869 He is wrong. The barrel bells do not get hot enough to burn out and they are not wet enough to rust out so they are permanent.

[@darrelllee6156]

contrary to the nay sayers, I would like to THANK YOU ! for your help in remaking the world a better place. your hard work rewards not only self ,but the rest of us. its so awsome that we have a tool like fire, that after thousands of years we can still learn better ways to use it. you are certainly a hero that saves life. your work will be built opon, the wise man built his house on stone. foundation is the key !

[@sukhmanicambridge]

This is amazing, I am not practical but am very inspired to be after watching this to learn what's possible!!! These are so way ahead of their time still.

[@jakebredthauer5100]

Walker's RMH is more advanced.

[@wambutu7679]

This video was an excellent grounding in the basics. Thank you.

[@Mark-xt8jp]

I highly recommend the books 'Rocket Mass Heaters' by Ianto Evans and Leslie Jackson, and 'The Rocket Mass Heater Builder's Guide' by Erica and Ernie Wisner. They have all the info needed to build a high quality RMH without making mistakes, and were written by the creator of the current RMH and by some of the cutting edge developers today. I've taken a RMH building class from Ianto and Leslie in Oregon, and I'm not sure where the idea that a mild steel barrel lasts for 1 to a few years with regular use. Ianto has a heater that sees constant use that has the same barrel now for 10-15 years, in the rain forests of the Oregon coast so plenty of humidity. If properly built and insulated around the heat riser and burn chamber, the barrel will get much more than 200 degrees... more like 600-800 F on the top but it does quickly drop going down the sides since the barrel radiates heat as part of the design. If built with low quality red brick and only a little insulation around the riser the temperatures are lower because it's less efficient. If you follow the books above guidelines on sizing, the exhaust will be under 150F and safe to touch. The cob heats up depending on how long the burn is. If you have a short burn, the cob warms up a smaller amount, and that amount goes up the longer you burn. So there is no absolute temp that the surrounding cob will stop at like suggested at 90F, that would be sort of low honestly. There are plenty of folks taking readings with digital thermometers after burns and 12 hours after, and the temps are around 140F soon after and 100F the next morning. The sizing of the feed, burn tunnel and heat riser is very much the key factors for developing the draft to prevent smoking back. There is a ratio to follow as a minimum: the riser should be 3-4 times taller than the feed, and the feed height plus burn tunnel length combined should be no more than the riser height. If the burn tunnel and heat riser are made from insulated bricks or refractory materials then the draft is much stronger/faster, as heat isn't being absorbed as much by the material before exiting the heat riser and you get a hotter burn. Hotter burn means more complete combustion and efficiency. It's not mandatory that the ducting after the manifold always angle upwards but you definitely don't want the ducting to dip down as there is always humidity in the exhaust gasses and that can condense in a dip and then rust out your duct in that spot. It would still be surrounded by cob but it would cause a little damage. Also as the exhaust cools off a bit, having the pipe closer to the surface further along can help evenly heat the surface so you don't have hot spots or cold spots. Having the duct sloped up a little bit makes this easier so I'm not saying 'dont' slope, just that it's not mandatory. 8)

[@karlbanks2653]

Thank for this input, valuable info.

[@jakebredthauer5100]

@@karlbanks2653 Walker Stoves has made some improvements.

[@karlbanks2653]

@@jakebredthauer5100 Thank you Jake :)) I’ll take a look. Happy new year to you.

[@jakebredthauer5100]

@@karlbanks2653 No ducting is needed in the bench bell. Matt Walker likes to use CFB, ceramic fiber board insulation and red brick (no cob, no barrel). He sells build plans. I consider him an expert specializing in design of RMH.

[@jeancampbell4341]

Very informative. Thank you for sharing your expertise.

[@WhatDadIsUpTo]

25:45 Barrel Size I use a 2/3rds section of a nitrogen "K" cylinder utilizing a 3" round vertical burn chamber within, fired with propane gas. The 3" x quare tubing exhaust travels a labyrinthine pathway through a small sand & cement bench in my bedroom, attached with a 4-bolt flange, terminating in an 18-feet-tall flu to a rain-proof termination cap. I installed a swing door on the flu to allow a candle to be placed on a wire rack inside the flu to act as a "flow primer". It takes about 2 hours to heat up, then I shut off the single burner, toss a pillow against the inlet, effectively spoiling any draft and sleep with the gas off. The warmed bench keeps my 15' x 15' room toasty warm all night.

[@brucea550]

Anyone seriously considering building one of these should look up Peter van den Berg who has vastly improved this basic design plus created a more woodstove type setup that doesn’t require feeding constantly with tiny pieces of wood. He is super intelligent and has done years of research on masonry heating for high efficiency.

[@InVinoVeritas.]

Great videos! When will part 3 be released? Thank you.

[@b_uppy]

Would be nice to see a system that could be done for travel trailer/tiny houses. I'd like a system for THOWs that is able to burn waste materials like corn cobs, etc, without taxing the stove, like to avoid the drum, too. Want to be able to cook on it in winter time, bake and heat water in an efficient system. Placing the tank in the apex under the roof uses wasted, hard-to-reach space and the water heater in the attic helps recapture lost heat, too.

[@harrymills2770]

Missed the answer on TEGs, which can be used with any heat source.

[@thoughtsfromathenasreality]

It started in Africa a thousand years ago. It can't be claimed by the Welsch.

[@jitaamesuluma9730]

You could warm water on it by wrapping copper tube round the inside of the chimney , the part that's hot

[@hafsalinda]

Be sure to put a steam collector in the end tube, cause if you heat water from inside thats all you will have left. Water turns to steam at 212f and riser temps regularly get near 1000°f. Dont make a closed steam bomb. Vent it to atmosphere.

[@stevenrobertson4470]

Another point, if one would want the flu gas entry area into the barrel to equal the area of the insulated clay chimney and assuming the chimney is square with inside dimension "s" and "h" representing the height of the barrel top above the chimney top, the equation would be: s^2 = 4 * s * h and solving for h:. h = s/4 ... This would suggest that the barrel top should be 1/4th of the inside length of one side of the clay chimney. If inside length were 4 inches, that would make it 1 inch.. This does not take form losses into account since the gas has to take a sharp, 90° bend... better stick with three inches to maintain adequate gas flow.

[@workinalday4351]

That duct looks like it is all galvanized! You should really find a safer material to use! That looks like heating duct for a hot air furnace which just carries warm air to vents, no issues. However if you are getting some really high heat, especially towards the stove side of the heater you can be releasing deadly toxic fumes into the house!

[@jamesglenn520]

No doubt!! Galvanized is really Toxic. You should only use Steel Stove Pipe! Galvanized Pipe is a very thin crappie quality of tin covered by the galvanizing process. Burn the coating off and you have tinfoil! Stove Pipe is quality steel and a heavier guage. It's also a good idea to use chimney tiles for the first few feet where the higher temperatures come out of the barrel 😀

[@alanschaller5869]

Add a few fins on the ducting to transfer heat to the cobb mass. Heat heat up the cobb mass quicker and transfer more heat to the cobb. The lower the exhaust temperature the more heat you are extracting from the wood you burn... more efficiency... Even adding a coil to heat water near the exhaust would be a way to extract even more heat... 200°F seems like there is still alot of heat energy to be extracted from the wood...

[@jakebredthauer5100]

The heat in the chimney is necessary to cause the draft. The mass does not need any tubes; it can be open space in the bench bell.

[@harrymills2770]

Once it gets going, it draws beautifully, but I think I'd use a rechargeable battery-powered blower to pull air through the system before it got going, and recharge the battery with a TEG that ran off the heat of the flue. These are notoriously smoky to get started, and his idea to fix is OK, but pretty crude and kind of vague with the 'T' idea. A blower, though, yes.

[@peterbeyer5755]

Harry Mills I use my hot air gun that I use for stripping paint, for a few minutes, I never have problems with smoke back.

[@GASNICABRUNATNA]

@@peterbeyer5755 used at the air inlet to also ignite the fuel?

[@unclebenny9028]

9:19 do you have any examples of a burned out barrel that must be replaced? I would like to analyze the failure points please...

[@jakebredthauer5100]

He was wrong.

[@jeffbrock4091]

we have had our rocket mass heater and the barrel looks new after 3 winters of use.

[@jamesglenn520]

It's been a few more years now. How is your barrel holding up?

[@jakebredthauer5100]

@@jamesglenn520 Barrel bells are permanent because they do not get too hot or too wet.

[@user-gw9dn2eo4u]

put cob layer inside the barrel too!

[@user-kk5ew7hd2g]

What kind of cob is used?

[@xeroinfinity]

Ive wondered, how long of tubes can you have coming off the main stove/drum that runs out, which is covered in cob? Ive read a few articles and none really mention the maximum length. I know at some point you would lose the heat efficiency and capability to heat the mass if it was to long.

[@brucea550]

50’ max minus 5’ for every 90° bend. It’s not about losing heat efficiency, but losing draft to exhaust the remaining fumes.

[@GASNICABRUNATNA]

Electric fan > pilot hole?

[@davidhayden9336]

how do you get the ash out of it? has anyone tried simply using fire brick motaror fire brick clay mixture and mold the whole thing?

[@davidhayden9336]

please disreguard, i was meaning to commit on another video.

[@goudhaantje3569]

The draft is caused by Hot air loosing heat to the barrel. Cooler air has lower pressure .

[@jakebredthauer5100]

I don't believe you. The draft is what the chimney is for.

[@goudhaantje3569]

@@jakebredthauer5100 Never mind. There is draft from high chimneys (pulling a vaccum of the pipe) and draft of heated air having less pressure at the outlet than the colder air in the inlet. A rocket stove works on this principle and must be pre heated a little to create the draft. Then if goes faster and faster making that sound.

[@jakebredthauer5100]

@@goudhaantje3569 Okay. The relatively cooler air outside of the riser will not be pushing in reverse (up) as hard as the relatively warmer air inside the riser is pushing forward (up). Basically, I am agreeing with you now. I will dispute that cooler air has lower pressure, if you will. Cooler air is more dense and more heavy and will sink down relative to warmer air. After that happens the air at the bottom is pressurized by the weight of the other air on top of it. The pressure of air depends on how it is confined. I won't say that either one has more pressure than the other. When air is confined and heated it will definitely increase in pressure. The air in the riser is rapidly expanding and may have very slight relative pressure that causes it to want to push in all directions. In this case the pressure is due to the expansion and not due to the relative temperature. The change in temperature is having the effect. Walker Stoves has done a lot of work on RMH and has developed a riserless core design for a stove. I think it still has separate stages for the first burn, second burn and heat extraction. He uses CFB and red brick.

[@kennapop3]

A recycled beer keg would work very well.

[@harrymills2770]

Kids have been around iron wood stoves for centuries. They can figure that shit out. For Pete's sake, a kid can burn themselves on a stove or a steam radiator or an electric heater. This is a fake concern raised by the audience member, who, I presume, never took his kids camping, for fear of killing them with the campfire. I would worry about the rocket stove wearing out, because of the refractory temperatures involved. If you don't know what you're doing, catastrophic failure by the outer "barrel" could burn your house down.

[@jamesglenn520]

I'm with you on that subject!! Ok little Johnny don't touch it's Hot! A day later little Johnny has a couple of red fingers and is crying 😢 See I Told you it was Hot 🤬 50 years down the road little Johnny is still not touching things that are Hot! Lol

[@Try_to_think_abc123]

Those members are the Karen's of society.

[@peterellis4262]

You could design a rocket stove with a pyrolysis chamber in it, but on their own rocket stoves burn fuel to ash extremely efficiently. While a rocket mass heater is designed quite intentionally to not produce high external temperatures, combustion within a rocket stove is happening at very high temperatures, in excess of 2,000 F . I'm not clear what form of electrical generation was being asked about, so I'm not at all able to respond to that. One of the issues in practical terms building rocket stoves/heaters is having materials for the heat riser that can survive the high temperatures within that space.

[@jakebredthauer5100]

Walker Stoves recommends ceramic fire board, cfb, for heat resistant insulation to use in cores.

[@Thomas-wn7cl]

Rocket Stove vs Masonry Heater Durability: I would go with a masonry heater. The rocket mass heater shown here is basically a thrifty copy of a Finnish Contra Flow masonry heater. However, a masonry heater is extremely durable. Some in Europe are over a hundred years old. Relitively speaking, the rocket stove seems to need constant rebuilding. Problems with code compliance: To the best of my knowledge, the International Residential Code, IRC, does not recognize rocket stoves, which means they cannot be legally installed in a home in the United States, which means no certificate of occupancy (CO), so you cannot legally live in your home. Although perhaps some sympathetic inspectors might consider it a fire place, or you may be able to get an engineer to design and stamp a design specific to you site, but engineers are insured too, and I do not know of any that would do this and the stamped design would likely be cost prohibitive anyway. Traditionally built masonry heaters are being incorporated into the building code. Furthermore, many of the images of rocket mass heaters in this slide shown do not appear to comply with IRC or NFSA setback to combustible materials requirement for an unlisted stove, so even a sympathetic inspector or insurance company would likely take issue. Insurance & Mortgage: I do not believe there are UL listed rocket stove designs, or NFSA recognized designs, which further makes that certificate of occupancy unlikely to achieve. Without the approval of the IRC, NFSA, or a UL listing, it is unlikely that an insurance company would insure you, or pay out in case of fire damage or personal injury. No CO or insurance means no mortgage, so good luck buying or selling a home with a rocket mass heater. I believe some masonry stove core kits might even be UL listed. Cost: To hire someone to build a masonry stove would be expensive, however to hire professioal to build a rocket stove would also cost a significant amount of money. Self built from a professional design would be the choice for either to keep the cost down. Further savings on a masonry stove could also be achieved by sourcing or repurposing inexpensive hardware. While I would go with a new firebrick core, sourcing or repurposing an appropriate yet inexpensive outer shell could also knock down the price considerably. Conclusion: So it may be appropriate tech for the developing world, I would stick with a traditional self built masonry stove for the industrialized world. Either way, the builder/owner should be compitent in their skills and most certainly do their due dilligence for the project.

[@marlonw5053]

I'd never get away with a new rocket-barrel DIY install where I live. But I could get a permit and install an EPA approved stove or masonry insert which uses kind of a similar principle; burn hot and clean. Let the masonry be the mass. Not cheap though!

[@Thomas-wn7cl]

@@marlonw5053 I looked into the new New York State IRC and masonry stoves are now included. I kick myself, but I saw a couple of pallets of mildly used fire brick for super cheap. If that was combined with salvaged outer brick or stone for the outer shell, and repurposed or generic hardware, then I think I could build one for around a $1000-1200.

[@RustyDagger-rl6jm]

Hey "rocket science", The black barrel doesn't radiate better because it's black LOL um, it would absorb infrared light better being black which of course it's not on the inside. (fukkin A)

[@ClovisX]

it amazes me how everyone is using a very stupid design for all their indoor rocket stoves

[@oriben-shir6742]

what designs would you have in mind?

[@stevenrobertson4470]

Yeah! It would be interesting to see your version which you feel is so much better.

[@jamesglenn520]

Would be awesome to hear some of your thoughts on a better design!

[@katiebea9258]

The guy must have been a total TROLL as it never responded

[@marlonw5053]

I find the barrels unappealing, but I think the point is supposed to be something inexpensive. And anyway, everyone is not just using barrels; there are bell and various masonry designs out there being used. There are EPA certified manufactured designs.