rocket stove and butt warmer

My son bought me a Ryobi laser thermometer for Xmas.  I am having so much fun with it as I slowly add the cob.  It does not work on shiny metal, as my burnt fingers can attest to!  It also only gives readings up to 650 F (+/- 5 F), so I can not measure the burn tunnel.

Anyway here are some numbers from my 8" system covered with a standard 55 gal drum:

The top was around 600 F over the burn tube and was as low as 500 F towards the edges.  On the side of the barrel it was around 400 at the top and 450 four inches down, then tapered off to around 250 at the bottom of the barrel.

The pot stuck in the clean out tube next to the barrel was around 180 at the bottom of the pot.  The exhaust was 83 F.

I have not been to a store to get PH strips yet. 

Today while working on the stove, my brother in law came up with a great idea.  We installed a piece of re-bar in the J tube about 2" from the back of the feed, at the height of the burn tunnel.  I load the wood in front of the re-bar towards the burn tunnel.

So far I would guess it has reduced the fire maintenance at least 50%.  Also since putting the re-bar in, I have had no smoke back or fire creep.  In effect I have an 8" x 2" air hole behind the fire wood.  The wood can not fall away from the burn tunnel until it has burned down below the top of the burn tunnel, which seems to keep it nice and rockety.  I'll keep it in this configuration for a few days but so far it seems to be a big improvement.

Cliff, I'm sorry -- I'm having a hard time picturing where the rebar goes.  Can you post a drawing showing how this is built?

http://sphotos.ak.fbcdn.net/hphotos-ak-snc6/hs003.snc6/165308_1592216997822_1007803355_31279218_3972167_n.jpg

Here is a pic looking down into the wood burn area, the burn tunnel is on the right.  I'm not sure how to post the pic directly.

<img src="http://sphotos.ak.fbcdn.net/hphotos-ak-snc6/hs003.snc6/165308_1592216997822_1007803355_31279218_3972167_n.jpg">;
Lets see if this works.  OK, the burn tunnel is to the right.

Good idea.  What you have basically done is added a separate draft to the system.

what i am looking at is 2 rockets . on on a lean to green houseprobally sand fill trench in concrete so it drains water any over flow  as well
the one in the barn on the other hand for cleanliness i would want to encase it in cement with top pointing clean outs.. and the first question
how log can the heat output .. that goes under the bench or under the floor

can 90 degree heavy cast pipe point down be used as the feed shute/chamber? so thereis no flas in the bottom and eleminates a ccorner .. or 45 degrees of it

careinke wrote:
Today while working on the stove, my brother in law came up with a great idea.  We installed a piece of re-bar in the J tube about 2" from the back of the feed, at the height of the burn tunnel.  I load the wood in front of the re-bar towards the burn tunnel.

So far I would guess it has reduced the fire maintenance at least 50%.  Also since putting the re-bar in, I have had no smoke back or fire creep.  In effect I have an 8" x 2" air hole behind the fire wood.  The wood can not fall away from the burn tunnel until it has burned down below the top of the burn tunnel, which seems to keep it nice and rockety.  I'll keep it in this configuration for a few days but so far it seems to be a big improvement.

Interesting, and congratulations on the innovation.
Do you mind saying what your fuel wood is?  We get our best results with a full wood box (mixed conifer and fruit woods), but I've seen systems with richer fuels (madrone and oak) do better on about the same amount of fuel in your picture.

Tinknal -  I think it's important that the air feed is not completely separate, but the air is still drawing downward through and past the wood.  We've seen people create a completely separate air feed with much poorer results.

sticky_burr wrote:
what i am looking at is 2 rockets . on on a lean to green houseprobally sand fill trench in concrete so it drains water any over flow  as well the one in the barn on the other hand for cleanliness i would want to encase it in cement with top pointing clean outs.. and the first question how log can the heat output .. that goes under the bench or under the floor

can 90 degree heavy cast pipe point down be used as the feed shute/chamber? so thereis no flas in the bottom and eleminates a ccorner .. or 45 degrees of it

Sticky Burr: You want to replace a known quantity (cob/adobe thermal mass) with two unknowns:
- sand (which is more insulative) and
- concrete (which is more conductive of heat, but prone to cracking and degeneration at high temperatures). 
- And you want these to work with various amounts of water/moisture. 
I don't think anyone can currently give you an accurate prediction of the thermal performance of your proposed system.  Maybe an engineer, if you can find one who is willing to get familiar with rocket stove dynamics first.
Not sure what you mean by "how log can the heat output"  - how to track it, or how long can the pipe still give off significant heat?

As far as cast pipe - eliminating the corner reduces the burn efficiency, this has been tried with thinner steel duct with disappointing results.  Also metal pipe gives some problems with thermal expansion, so you need expansion joins that don't leak gas, yet protect the masonry from cracking.

As always, try it outside as a prototype first, and then transfer what you've learned to your final system.  Working from the book Rocket Mass Heaters would be a good idea to avoid some common problems.  http://www.rocketstoves.com
or if you prefer official-type language, you can get a sneak preview of a proposed building code for these things, at http://www.ErnieAndErica.info/rocketmassheaterpermitting

Please let us know how it works out with the concrete thermal mass, I don't know anyone who's tried it yet.

-Erica Wisner

careinke wrote:
Today while working on the stove, my brother in law came up with a great idea.  We installed a piece of re-bar in the J tube about 2" from the back of the feed, at the height of the burn tunnel.  I load the wood in front of the re-bar towards the burn tunnel.

Interesting idea, just thinking this would act as an air wash and perhaps permit the installation of a window for viewing the fire without having the "glass" subjected to too much thermal shock and splitting.  Be something to try anyway.

Erica, just looking at your permitting page and it indicated no dampers.  Just wondering about preventing cold air backing into the system if the wind happened to be from the wrong direction say?  Perhaps not too great a problem in the pacific NW but arctic temperatures (-30 celsius) and swirling winds are not uncommon here in NE Ontario.

Erica Wisner wrote:


Tinknal -  I think it's important that the air feed is not completely separate, but the air is still drawing downward through and past the wood.  We've seen people create a completely separate air feed with much poorer results.

-Erica Wisner

I understand this.  By putting in that rebar  they improved the airflow without actually adding a separate draft.

Erica Wisner wrote:
Interesting, and congratulations on the innovation.
Do you mind saying what your fuel wood is?  We get our best results with a full wood box (mixed conifer and fruit woods), but I've seen systems with richer fuels (madrone and oak) do better on about the same amount of fuel in your picture.

Tinknal -  I think it's important that the air feed is not completely separate, but the air is still drawing downward through and past the wood.  We've seen people create a completely separate air feed with much poorer results.

Erica,

I have a large variety of wood from the property.  Probably half is broad leaf maple, with Hemlock, Doug Fir, Alder, and Cherry thrown in.  The maple works pretty well, but if I want to crank it up, I add Doug fir or Hemlock.

Yesterday I moved the re-bar back so the airflow gap was only about an inch.  I had two fire creeps when using fir.  I think I will put it back in the original position.  I think we got lucky and guessed right the first time.

It is a pretty easy mod, and can be removed if it does not work.  It would be nice if some others would try it out and see how it works for them.  As always, my ideas are public domain, feel free to steal and use in any way you want. 

I just wanted to tell everyone with questions and ideas to build rocket stoves to heat a room, or house, barn or power a space ship, to start out here and read this thread to get a basic understanding. Advanced info is here too...ALSO at the bottom of each page Paul has a book listed that will save you a lot of time and money do do it right the first time and save you from re-building.

Other threads with RMH in alternate energy are also about Rocket Mass Heaters.

Seven examples of the rocket mass heater draw and/or the sideways fire / burn that is an essential component of the rocket mass heater.  You can see the fire / flames actually going sideways.  And you can see the smoke re-burning and making the rocket sound - sometimes with fire coming out the top of a chimney.

This shows several examples of dry stacked bricks that will eventually be a rocket mass heater core - complete with fire dmonstrating the sideways burn and the draw. 

Appearances by Geoff Badenoch, Caitlin Elder and Ernie Wisner.

Several clips of the portable rocket mass heater. 

Paul I'm moving to Florence this summer and want to sart building by next spring 2012.

I would love to visit you this spring if you have time. I would love to get a list of alternative homes that have been built in the area.

I am looking at several work shops this year, a ten day in Austing for Cob and Straw bale and one in Tennesse for flooring. Do you have any ones that you can recommend that would help get me started?

At last, I put the final coat on my Green house RMH.  Here is a short vid showing it off.

http://www.youtube.com/watch?v=QpJLS3eD6Po

Cliff

Looks good Cliff - gave a thumbs up..

Yeah, that looks really nice.

Talking about temp, I would like to know how big of a gap between heat riser and top of barrel.  Everyone seems to have some higher temps than do I.  Mine can burn the fingers but I can touch it quick without to much problems.  200 degree temp is pretty much max on top. 

Using a 1 3/4 inch gap on 6 inch system.

sixnone wrote:
Talking about temp, I would like to know how big of a gap between heat riser and top of barrel.  Everyone seems to have some higher temps than do I.  Mine can burn the fingers but I can touch it quick without to much problems.  200 degree temp is pretty much max on top. 

Using a 1 3/4 inch gap on 6 inch system.

I don't know for sure. how hard is it to change? 1 1/2 inches gives the same CSA as the 6 inch pipe (6X3.14X1.5=28) I would try that first. I read that changing the gap moves the heat torus up or down so you may have the highest temp down from the top a bit or have spread the heat out a bit. I am not sure that this would make the mass get hot any slower though... is there any reason you want the top of the barrel real hot? Is the rocket force not strong enough?

Len wrote:
I don't know for sure. how hard is it to change? 1 1/2 inches gives the same CSA as the 6 inch pipe (6X3.14X1.5=28) I would try that first. I read that changing the gap moves the heat torus up or down so you may have the highest temp down from the top a bit or have spread the heat out a bit. I am not sure that this would make the mass get hot any slower though... is there any reason you want the top of the barrel real hot? Is the rocket force not strong enough?

My thoughts are, if its not broke, dont fix it.  It works fine and as it should.  Its safe.  But its not the same as boiling water in a pot like you would over a rocket stove vs. rocket mass heater.  Maple syrup time you know?

Question: Ok, so you seemingly have an efficient wood stove - the problem that is apparent to me is that with this design, you have effectively created a negative pressure in the house (since the draft that makes the fire burn sideways is sucking hair out of the building.

It would seem that you would need an air exchanger box (adjustable) to fuel the wood feed so that the draft that is being sucked in (and then out) is fresh air, instead of air from the house.

Does that make sense or I am misunderstanding something?

Kegs wrote:
Question: Ok, so you seemingly have an efficient wood stove - the problem that is apparent to me is that with this design, you have effectively created a negative pressure in the house (since the draft that makes the fire burn sideways is sucking hair out of the building.

It would seem that you would need an air exchanger box (adjustable) to fuel the wood feed so that the draft that is being sucked in (and then out) is fresh air, instead of air from the house.

Does that make sense or I am misunderstanding something?

All, wood (or gas, or oil) burning appliances do that... from fire places to gas furnaces. It was popular to use an external air source for a while but I think I read somewhere it was found to be unsafe in some cases. Something about gases going the wrong way at any leaks in the system. The good thing with a massheater though is that you are warming mass... and the people instead of the air. So this is less of a problem than it may seem. The reports from people who have them is that the homes are comfortable.

Len wrote:
All, wood (or gas, or oil) burning appliances do that... from fire places to gas furnaces. It was popular to use an external air source for a while but I think I read somewhere it was found to be unsafe in some cases. Something about gases going the wrong way at any leaks in the system. The good thing with a massheater though is that you are warming mass... and the people instead of the air. So this is less of a problem than it may seem. The reports from people who have them is that the homes are comfortable.

Interesting.  I guess I will just have to experiment with some designs in a temporary tight shelter and measure air balance to modify from there...

Hi All,

New to the forum.  Looks like a great place.

One question that has been bugging me regarding rocket mass stoves, or any fireplace for that matter is the effect of air intake cooling your home.

When you're operating any fireplace (rocket stove or not), if your air intake is within your home you are effectively creating a vacuum inside your house, pulling cold air into your house. 

Why not put your feed box on the outside of your home and pipe the hot exhaust into your house?  This way the air going into and out of the stove is from the outside and you don't pull cold air into your house. 

You could keep the feed box inside your house for easy access so long as their's a door flap over it and an air intake pipe leading to the outside.

Thanks.

Matt

Matt Hennek wrote:
Hi All,

New to the forum.  Looks like a great place.

One question that has been bugging me regarding rocket mass stoves, or any fireplace for that matter is the effect of air intake cooling your home.

When you're operating any fireplace (rocket stove or not), if your air intake is within your home you are effectively creating a vacuum inside your house, pulling cold air into your house. 

Why not put your feed box on the outside of your home and pipe the hot exhaust into your house?  This way the air going into and out of the stove is from the outside and you don't pull cold air into your house. 

You could keep the feed box inside your house for easy access so long as their's a door flap over it and an air intake pipe leading to the outside.

Thanks.

Matt

I just wrote about the negative pressure issue 3 posts ago.  This is absolutely correct.  However, you don't want to pipe an exhaust from any wood stove into the house for the simple reason that it's not going to have 100% combustion at all times, which without the means for full combustion, you will produce some amount of carbon monoxide, which is of course poison gas.

This system needs an air intake.  FOR SURE.

New construction codes in my state require combustion air to be incorporated into the design of a wood fired stove for a very good reason.

The problem with the rocket stove so far as I see is that its current design (I do not own the book, but have seen Paul's videos and have looked elsewhere on the internet where I have found several other designs) is that is has effectively been designed for use in the outdoors only, or where a little drafts and dust is okay.  This is not a very good design for an efficiently built (e.g. "tight" heavily insulated) home, which is extremely important for Northern climates.  

People may have these in their homes currently and find them comfortable, but if they use the current design, they are absolutely creating a negative air pressure in their homes, and that air is being pulled through any cracks in the seams of the home construction, effectively creating drafts and dust, among other problems (such as permanent leaky seals of windows and doors).

The solution of course is to design the fuel box with a fresh air feed that is fully insulated and adjustable from open to fully closed.  I would expect that in order to work effectively, this tube needs to be installed at a lower height than the rocket combustion chamber.

Another issue is the exhaust vent.  You can't have this open, or just have a stove pipe sticking out an 8" hole in your wall or ceiling as I have seen on the examples.  It needs to be very much insulated between the thermal mass and the outlet (or it will transfer cold through convection), and some form of closure needs to be installed on the exterior to ensure animals (insects, birds, spiders) do not build in the tube.

I think other parts of the design are exceptional and superior to current interior wood stove systems.  

The extra efficiency of the combustion chamber seem to solve the problem of the ~75% efficiency of the current "high efficiency" wood stoves being sold commercially.  A wood stove with 95% efficiency will solve a whole lot of energy and heating problems worldwide.

   

Len wrote:
All, wood (or gas, or oil) burning appliances do that... from fire places to gas furnaces. It was popular to use an external air source for a while but I think I read somewhere it was found to be unsafe in some cases. Something about gases going the wrong way at any leaks in the system. The good thing with a massheater though is that you are warming mass... and the people instead of the air. So this is less of a problem than it may seem. The reports from people who have them is that the homes are comfortable.

Len - I checked about the external air source issue.  It isn't found to be unsafe, but rather it is required by new building codes. 

It may be nice feeling comfortable (and that is what it is all about right?), but negative air pressure caused by feeding air through the stove will ultimately have to pull outside air from somewhere inside the house - and that somewhere is between gaps in doors, windows, foundation sill area, roof vents, etc.  - all areas where ventilation is not currently controlled.  This is more of a problem than you may be aware of.  It increases dust, moves mold spores and other potential pathogens around, permanently breaks seals so that even when the negative pressure stops, cold air leaks out and insects and spiders find ways in. 

All this can be prevented by incorporating a fresh air feed into the unit.  Really, that's not hard at all do do either!

Kegs wrote:
 This is not a very good design for an efficiently built (e.g. "tight" heavily insulated) home, which is extremely important for Northern climates.  

People may have these in their homes currently and find them comfortable, but if they use the current design, they are absolutely creating a negative air pressure in their homes, and that air is being pulled through any cracks in the seams of the home construction, effectively creating drafts and dust, among other problems (such as permanent leaky seals of windows and doors).

Ok, that makes sense.... building codes for "tight" heavily insulated homes also require air exchanges. That is once you tighten the home so there are no air leaks, you have to (by code) put a leak in and then drive it with a fan. This applies to homes even with no wood or gas burning appliances. There are heat exchange products out there that try to save the heat from exhausting to heat the incoming air... but few contractors do (unless told to) as it doesn't sell a spec home. So there has to be incoming air anyway, why not use the stove to exhaust it? If you have a tight home and have to run a fan anyway then drag your intake air past some of the warm mass some where that it is not radiating to your room... only one problem is that a fan requires power. but the time you are sure to be using the stove is when there is none. Make sure your design allows a second source of air... both for the stove, but also to breath. Having a stove that pulls air through the living space first could be life saving.

Kegs wrote:
Len - I checked about the external air source issue.  It isn't found to be unsafe, but rather it is required by new building codes. 

Yes but it doesn't have to be sealed. Any home has to have proper air input to cover all use including breathing. using leaks in walls etc. is not the best way. but it still has to be there. The air has to be exchanged.

Fresh air intakes are required by code because if you seal a house and do not bring new air in the house will become unhealthy and ultimately unsafe to live in.

I renovated a 100 year old home, sealing much of the house, but not everywhere. I intentionally left a couple spots open. The reason for this is that the house was heated with a gas boiler. Our neighbor sealed his house a couple of years earlier. Did a good job, added insulation, new high efficiency boiler boiler, etc. One day he had some people over for dinner, nice casual evening with good discussion... then they all started to get headaches, one person got nauseated... Lucky for them one of the guests realized what it might be and insisted that they open all the doors and some windows. They were all being gassed by Carbon Monoxide.

When he sealed the house he neglected to add a fresh air intake. That meant that the furnace eventually sucked much of the good air out of the house and was no longer venting properly. The exhaust started to collect in the house.

The old houses were designed to leak air. This was an intentional thing to try an improve the air quality. Think about all of the materials we have in our houses now that offgas VOCs. If you do not have fresh air circulation to dilute those VOCs, you will create a toxic environment in your house, even if you have good exhaust for the fireplace.

For myself I like the idea of the fresh air intake that feeds directly into the fireplace. BUT, I also want a bit of air exchange happening in the rest of the house as well. Setup the air intake "near" the fireplace maybe. Run the pipe past the heated mass to temper the air, but allow it to mix with the room air before entering the fire. This will help to clean the air in the room. If you are concerned about dust/pollen/spores then include filtration into that intake. You can have multiple filters and still get air flow. It just wont be as fast an exchange rate.

The point is managing the system.  The HVAC of course needs two systems - if one were to incorporate tight construction, a rocket stove with a fresh air intake and an properly designed air exchanger, that would solve the problems I was mentioning earlier - since your air would be entering and exiting a controlled location allowing for a neutral exchange of fresh air. 

No filters would be necessary, as it wouldn't be pulling air from areas (such as sill locations) which are right at the level mold spores are outside while it rains, and dust when it is dry.

Kegs,

Totally true. Plan it out and then manage it. If you don't take care of it, it doesn't matter if you have a good system in place.

My preference is a passive system if at all possible, but it is harder to keep the air exchange rate even and adequate. It would be great if the amount coming in and going out could be the same all the time and remain passive but that is not possible. The compromise is sizing the intake to match the fireplace outflow, then seal everything else perfectly.

Just for interest... The university my wife works at has codes in place that insist that all office space have an air exchange rate of 4 times per hour, that means all the air has to be changed 4 times every hour. BUT, for the animal lab she runs, the animal housing areas must have an exchange rate of 12 times an hour! That's right, the rats and mice must have an exchange rate 3X greater then the humans. They must have cleaner and fresher air then the people working in the same building. The animals even have their own ventilation system that is separate from the human system.

RMH and well insulated air tight homes.... and the grid and off the grid and code. All fun stuff. Code is there to keep people out of court, it is part of the grid tied world. The house is lightly build and so has to be well insulated and as air tight as possible to use less grid. The thermostat is on the wall ... set it and forget it. Once there is no grid and power is not assured... a tight house starts to make less sense. There is no guarantee of a fan to move air. Heat comes from wood that they have chopped not the flick of a switch. Any, materials for building or repairs either come from the ground (dirt, trees, etc.) or cost much to truck to the site. In this case a high mass house may make more sense.... In fact in a world where energy is running out, grid reliance may not be a great idea. This is the background the RMH came out of. Not the world of contractors and high profits. Built with on site materials it is a high mass heater at a fraction of the cost of a masonry heater. It is not expected to keep air temperature within .5 degrees, but to keep people comfortable who are used to spending a lot of time outside (getting wood, food, etc) who think nothing of changing the set of clothes to regulate body temp and will seek the warmest place in the room rather than heat the whole living space to 72F even when they are sitting in one room for hours and in fact may not enter some rooms for weeks. This is not to say these people want to where outside clothes in side, they want to remove their parka or rain coat when entering too. But a light sweater is not a problem. So that is where the RMH started. It worked well... really well and now people want to use it on their grid tied home. Great stuff. But now there are other concerns like making sure there is enough oxygen for the fire as well as the people. Those used to a thermostat way of life will have some learning curve... any good wood appliance requires some skill to operate properly, it is some steps beyond the set the thermostat kind of house. People do die if they get it wrong. I personally do not think any amount of new code will change that.... some people can do anything wrong. So far building a RMH to code is a bit of a dream, though some people are working to change that, they are either built where code is not a concern or on the sly without permit.

Very good thoughts Len.
Very true.

Wow, that post is full of so many assumptions that are more imaginary based rather than reality based I have no idea where to even start, but I'll give it my best:

1. The obvious reason for building codes is safety, not to prevent litigation or promote economic consumption.

Without a question, building code has saved lives.  Some examples?  Span lengths of dimensional wood (keep roof or floor from falling in because of insufficient support), fire code drywall required between garages and occupied areas (resists fire and allows for additional time for occupants to exit house in cases where fuel catches fire), GFCI switches in bathrooms (prevents electrocution) and numerous other codes which prevent dangerous situations from happening.

2. There isn't any part of the known Earth's inhabitants that don't rely on some outside trade which includes products not directly acquired from primary (natural) resources.

3. Every example of a RMH design in any videos or pics I've seen have used metal pipe.  Clearly this has not been procured directly from primary resource extraction.  Everything starts there, but stove pipes are a manufactured product, not a primary resource.

4. Many homes in the developed world, regardless whether they have commercially supplied utilities or not, are heated with wood fired heating systems.  Such systems do not necessarily require a thermostat.  For sure, many homes do have a thermostat, but many do not.

My own home has this possibility, though I have decided to rely on a geothermal system simply because I was not aware of a more efficient system when we built this home.

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Let's get real.

Humanity is not very likely going back to the Paleolithic age anytime soon.  

Humanity is currently in a changing environment of burgeoning populations built on a system of cheap efficient energy (oil) that is a temporary, decreasing non-replaceable resource.

Once that resource no longer becomes affordable to extract (and that period will come sooner than most imagine), there will be an energy crisis.

The U.S. is in an economic pinch due to a history (directly parallel with oil use) of over consumption of material goods and an inefficient use of primary resources.  

Many changes are going to prove necessary, including the level of all energy systems efficiency.  This includes heating.  It would be foolish to think that RMH design is not going to be produced commercially soon to combat current heating inefficiencies.

Personally, I do not think "off the grid" necessitates avoiding the consumer economy, since that really isn't much of an option if you think about it.

Getting away from commercial power however is an option.  This doesn't mean you have to build things illegally - after all "on the sly" means illegally, since following building codes is a legal requirement for the construction of an occupied structure anywhere in the developed world.

I have no idea where you are coming from, but I see a lot of future for the RMH design and if this design provides an efficiency advantage from typical wood stoves (which certainly it appears that it does), it will soon proliferate on the commercial market.

I know I will be incorporating the RMH design in a heating element of the next occupied structure I build.

Best Regards,
Kegs

Len wrote:
RMH and well insulated air tight homes.... and the grid and off the grid and code. All fun stuff. Code is there to keep people out of court, it is part of the grid tied world. The house is lightly build and so has to be well insulated and as air tight as possible to use less grid. The thermostat is on the wall ... set it and forget it. Once there is no grid and power is not assured... a tight house starts to make less sense. There is no guarantee of a fan to move air. Heat comes from wood that they have chopped not the flick of a switch. Any, materials for building or repairs either come from the ground (dirt, trees, etc.) or cost much to truck to the site. In this case a high mass house may make more sense.... In fact in a world where energy is running out, grid reliance may not be a great idea. This is the background the RMH came out of. Not the world of contractors and high profits. Built with on site materials it is a high mass heater at a fraction of the cost of a masonry heater. It is not expected to keep air temperature within .5 degrees, but to keep people comfortable who are used to spending a lot of time outside (getting wood, food, etc) who think nothing of changing the set of clothes to regulate body temp and will seek the warmest place in the room rather than heat the whole living space to 72F even when they are sitting in one room for hours and in fact may not enter some rooms for weeks. This is not to say these people want to where outside clothes in side, they want to remove their parka or rain coat when entering too. But a light sweater is not a problem. So that is where the RMH started. It worked well... really well and now people want to use it on their grid tied home. Great stuff. But now there are other concerns like making sure there is enough oxygen for the fire as well as the people. Those used to a thermostat way of life will have some learning curve... any good wood appliance requires some skill to operate properly, it is some steps beyond the set the thermostat kind of house. People do die if they get it wrong. I personally do not think any amount of new code will change that.... some people can do anything wrong. So far building a RMH to code is a bit of a dream, though some people are working to change that, they are either built where code is not a concern or on the sly without permit.

Interesting.  The only number I have seen from commercial air exchanger website is 0.35 air changes per hour.

This Canadian site suggests 0.3 ach:

http://www.nrc-cnrc.gc.ca/eng/ibp/irc/ctus/ctus-n14.html

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I believe the 4x/hr. air exchange rate is not for outside to inside air, but rather recirculation within the building with rates as suggested here:

http://www.engineeringtoolbox.com/air-change-rate-room-d_867.html

I do not think it would be thermally possible to heat that much air in any building, regardless of the "mass" of the building.

It is interesting, none the less.

It would be even more interesting to see the requirements for laboratories dealing with high level infectious diseases.   

klorinth wrote:
Kegs,

Totally true. Plan it out and then manage it. If you don't take care of it, it doesn't matter if you have a good system in place.

My preference is a passive system if at all possible, but it is harder to keep the air exchange rate even and adequate. It would be great if the amount coming in and going out could be the same all the time and remain passive but that is not possible. The compromise is sizing the intake to match the fireplace outflow, then seal everything else perfectly.

Just for interest... The university my wife works at has codes in place that insist that all office space have an air exchange rate of 4 times per hour, that means all the air has to be changed 4 times every hour. BUT, for the animal lab she runs, the animal housing areas must have an exchange rate of 12 times an hour! That's right, the rats and mice must have an exchange rate 3X greater then the humans. They must have cleaner and fresher air then the people working in the same building. The animals even have their own ventilation system that is separate from the human system.

Kegs,

You are completely correct. I missed a key detail and misspoke, recirculation not exchange. The exchange rate is controlled for the entire building along more "normal" rates.

Thank you.

Kegs wrote:
Wow, that post is full of so many assumptions that are more imaginary based rather than reality based I have no idea where to even start, but I'll give it my best:

I have explained things wrong or poorly and so you seem to have missed the point.... I will try removing one foot from mouth so I can insert the other...

1. The obvious reason for building codes is safety, not to prevent litigation or promote economic consumption.

municipalities have been sued for houses that have fallen down after they have signed them off. I agree that is safety. It is not a one or the other thing.... though I am trying to understand how having outlets a certain spacing is about safety. Anyway, that is not my argument and probably better left unsaid.

2. There isn't any part of the known Earth's inhabitants that don't rely on some outside trade which includes products not directly acquired from primary (natural) resources.

missed the point again. I was merely referring the average contractor stick houses that crowd our urban areas. built and designed to be grid connected. The point was that the RMH was originally used in cob houses as part of their design. These are not high insulation houses, but high mass houses in the same way the RMH is a high mass heater.

3. Every example of a RMH design in any videos or pics I've seen have used metal pipe.  Clearly this has not been procured directly from primary resource extraction.  Everything starts there, but stove pipes are a manufactured product, not a primary resource.

missed the point.... the metal parts of a RMH by mass are a very small percentage of the heater. What makes it work is the large amount of site supplied mass. The metal parts are used because they could be found used and generally free or cheap. This is not a get away from technology deal, but using the right technology for the situation.

4. Many homes in the developed world, regardless whether they have commercially supplied utilities or not, are heated with wood fired heating systems.  Such systems do not necessarily require a thermostat.  For sure, many homes do have a thermostat, but many do not.

The average subdivision? are you talking percentages? Even in the small city I am in (20000) the percentage of homes using wood for heat is small, even though wood is plentiful. All of the new houses I have seen built are gas heated and electric blown. The most common upgrade is to a heat pump sometimes with a loop underground in the yard. All power reliant. The area I came from with some millions of people had next to no wood burning heat because it was too hard to get... maybe some pellet stuff....

My own home has this possibility, though I have decided to rely on a geothermal system simply because I was not aware of a more efficient system when we built this home.

probably for an insulated stick built home you are right.... better than gas anyway. My home went down about $200 a month going from gas to electric... because I can spot heat when/where needed and perhaps the gas system was not very good. Heat pump may be better but I don't have the capital to do that.

Let's get real.

Humanity is not very likely going back to the Paleolithic age anytime soon.  

was there ever a question or suggestion of that? I am not suggesting going hunter gatherer.... The RMH is too big to move from place to place just for a start... yes "let"s get real".

Personally, I do not think "off the grid" necessitates avoiding the consumer economy, since that really isn't much of an option if you think about it.

I am sorry you got that idea from what I posted... I think it is kind of a long stretch.. community is very important for a person's mental health and generally there are people better at doing things than I am.

Getting away from commercial power however is an option.  This doesn't mean you have to build things illegally - after all "on the sly" means illegally, since following building codes is a legal requirement for the construction of an occupied structure anywhere in the developed world.

I was not encouraging people to do things outside of the law, just pointing out that any RMH built where codes apply was probably illegal. also that there is an ongoing effort to change that by bringing engineering and spec to the RMH.

I have no idea where you are coming from, but I see a lot of future for the RMH design and if this design provides an efficiency advantage from typical wood stoves (which certainly it appears that it does), it will soon proliferate on the commercial market.

maybe. From some of the discussion I have seen, the RMH is not more "efficient" (or very little more) ... we had someone with a lot more knowledge than most of us set us straight on that... it does tend to be more effective when used right though. I personally think part of this is designing the house around the heater instead of designing the house and then deciding how to heat (see the discussion above on air exchange for one, but I have also seen that people design so that the RMH can be a part of as many rooms as possible). It is not a good heater for a large house unless you are just interested in heating one room with it. It also falls short in a tiny house where it may take too much space. It has been interesting to study masonry heaters and the houses designed around them both recently and in ages past and depending on the climate where they where built. The RMH shares a lot with them.

I know I will be incorporating the RMH design in a heating element of the next occupied structure I build.

I had thought the same... I am not sure at this point if I will. I have a pile of bricks and barrel to play with and have started building a temporary one in the back (not in a living space) to play with and see if it will fit into what I would like to do down the road. I suspect the easiest way to make a RMH that is within code or that can be permit-ed would be to enclose the whole smoke path in steel to ensure it is air tight and add the mass on the outside and fire brick on the inside for the riser and feed. It would cost more to build.... but there would be no smoke leaks from cracked cob either. I also think that the foundation would need to be engineered to support the weight just the same as with a masonry heater (or a masonry fireplace for that matter). I am not sure anyone has worked out what the weight of a RMH per sqft would be... and then they are all unique. In the end I don't know that building a masonry heater would end up costing any more than a "permitted" RMH... and I could get better cooking out of a masonry heater too (at least with the state of the art in RMHs). The RMH has some great stuff going for it, but it needs some work in the design end before it becomes "mainstream" (if it ever will, masonry heaters, while big in Europe are scarce in North America). There is still lots of room for tinkering....

Nothing to do with RMH, but Len wondered ....

... though I am trying to understand how having outlets a certain spacing is about safety.

Common appliances have a maximum cord length of six feet, counter-top appliances have cords two feet long.  The minimum spacing requirements are to prevent people from needing extension cords strung over the floors or counters, avoiding trip hazards and fire hazards (from the cords overheating).

Len wrote:though I am trying to understand how having outlets a certain spacing is about safety.

Yeah, you and me both.  That part does perturb me.

The average subdivision? are you talking percentages? Even in the small city I am in (20000) the percentage of homes using wood for heat is small, even though wood is plentiful. All of the new houses I have seen built are gas heated and electric blown. The most common upgrade is to a heat pump sometimes with a loop underground in the yard. All power reliant. The area I came from with some millions of people had next to no wood burning heat because it was too hard to get... maybe some pellet stuff....

I do wonder how the massive populations are going to heat once oil is gone.  I just read an article suggesting oil will be completely exhausted by 2049.  I suspect it will be quite some time before that.  Obviously, oil is what fuels commercial transportation of oil, timber, coal stone, plutonium, wind turbine blades, photovoltaic panels, ore and most other primary commodities, including food where it can't otherwise be grown.

I do not know the answer.

Heat pump may be better but I don't have the capital to do that.

It cost us $10k to put this in our 1560 sq. ft. house in 2002 - and we do not have a closed loop.  I wish we did.  That would save us a lot of hassle, but that's ANOTHER $10k (at least).  Yeah, they are NOT cheap...and still you're on the grid.  It's got a compressor which surges a LOT of amperage and would probably be quite difficult to run using alternative energy alone.

From some of the discussion I have seen, the RMH is not more "efficient" (or very little more) ... we had someone with a lot more knowledge than most of us set us straight on that...

Well this is interesting - can you share any links on that?

The RMH has some great stuff going for it, but it needs some work in the design end before it becomes "mainstream" (if it ever will, masonry heaters, while big in Europe are scarce in North America). There is still lots of room for tinkering....

Yeah.  Awesome to hear you are going to be playing with this.

Thank you for your reply!!!

Kegs wrote:

Well this is interesting - can you share any links on that?

This link should be page two of the thread. The interesting explanation is towards the bottom of the page.

https://permies.com/bb/index.php?topic=6199.40

Professor Rich takes a scenario with two kinds of stoves, one a mass heater and one an iron stove and makes them 100% efficient(no flue... no people either but works for calculations).  He uses a known amount of fuel in each (a one pound propane cylinder), and then shows where the heat goes. Basically more of the heat produced in the mass heater stays in the room and so the mass heater is more effective even though it is running at the same efficiency.

A mass heater masonry or rocket work on the same idea and are very close to each other in effectiveness. The RMH can be cheaper to build, has some iron exposed for more instant heat to a cold room and uses fuel at a slower rate due to the small size of the burn chamber. The masonry heater is also a mass heater, but uses pre-made firebrick core and brick facing which is generally more expensive and requires more skill to build. However, the masonry heater is a batch heater where you burn a load of wood once every 12 to 24 hours... light and forget pretty much instead of feeding all the time like the RMH for the length of burn (the RMH burn is about the same length as the masonry heater, not constant like an iron stove).

Both Mass heaters add mass to the living area which helps in both summer and winder to temper the inside environment.... that is in the winter heat comes from the heated heater over a long period of time and in the summer the mass absorbs heat during the day to keep the house cooler and looses it slowly at night to the breeze when we leave our windows open.... A house with lots of mass in the walls and floors (inside the insulating layer) has some of this same effect.

The major advantage to a masonry heater right now, is that it is much easier to get a permit for it.... as such, if you need a permit where you live, the masonry heater may end up being cheaper... and less stressful. You may even be able to face it with cob, I have seen them faced with earth bricks made on site. I think if the RMS heater was treated as a masonry heater with a separate core and facing... the core is the part that needs the most engineering, so if a standard core could be designed that can be standards approved (CSA in Canada, UL or EPA in the US) then the facing could be much easier to deal with... it would still have to be fireproof... but cob should be possible.