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Posts Tagged ‘wood stove’

I have a ridiculously short attention span. I’ve probably mentioned that before. I’ve done, what I consider, well with maintaining this blog over a three year period but I’m finding it increasingly difficult to come back to with all of my other interests taking priority. Anyway, it occurred to me that I have not updated this page since our mass heater fiasco and the ensuing mad dash to replace it with a working stove.

After all of the effort required to take this project this far though, I do intend to finish it with our experiences actually living in the off-grid home we worked so hard to complete. So you can expect, sporadic (as usual) updates over the winter and into the spring and we’ll see how I feel about writing anything more (on this subject) at that point.

We’re doing fine- I’ll start with that as I keep getting asked. We’re not freezing. Quite the opposite- there are times when I have to strip down because it’s so hot in here, but I am absolutely not complaining. The humidity that some of my readers were wondering about is pretty much non-existent, with the wood stove drying things out enough that I have to keep a pot of water on the stove to add humidity.

Our solar power is serving us quite nicely, but we don’t have the loads that we did at the other house. More on this in another blog. Suffice to say that I don’t worry about having lights on, or running my computer (and Shane’s five computers), or the speakers, or the fridge and freezer. (Though I will say that Shane’s constant hovering is enough reminder to conserve energy, in addition to being annoying.) We do, however, have generators just in case, or to equalize the batteries during the long, dark winter.

I’m still adjusting to using a wood stove for all of my cooking. My breads turn out beautifully, as do pizzas, stews, stir fries. More precise cooking (like my delicate cookies, or yoghurt) will take a while to perfect. Sometimes I am beyond impressed with my newfound abilities and other times I can be found swearing a blue streak in front of the stove. It’s alright though- I have been swearing a blue streak over something since I was yea high; if it weren’t the stove it’d be something else. “Hot little pistol with a potty mouth,” is how Shane sometimes describes me, which simultaneously makes me laugh and creeps me out (who uses the expression “potty mouth”??).

Bearing in mind that this entire thing was one grand experiment for us, a couple of ‘city folk’ trying to see just how far we could take an off-grid lifestyle, we’re doing quite well overall. I haven’t taken photographs of the entire interior yet but I’ll leave you with a view of our living room. It’s not finished (since our rocket mass heater demolition) but it’s as finished as it will be until spring.

LRoom
LRoom2

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All of the really good ideas we’ve gone with have also been the simplest. Go figure. So we’ve been hammering out a plan for weeks now, trying to decide on the best possible stove top using the least amount of fuel. We worked with ideas using firebricks, and all sorts of designs, and we finally settled on a modified rocket cook stove. Simple.

Shane dragged in a barrel (yet another left behind by the previous owner) and we took the measurements before he set a fire in it to burn off the residue. We were hoping the paint would burn off too, as it has with other barrels, but it required a bit of sanding.

We used standard black stove pipe to build a sort of J-tube. Had to chop down a piece of pipe to get it just the right length but it’s a perfect fit now. Another length of stove pipe will be the riser, and we’ve got some old metal from a water heater that we’ll chop and use as a sleeve around the riser, to fill with insulation.

A chimney will exit out the lower third of the barrel and outside of the house. The whole deal will be insulated and plastered in so that it retains the heat where needed and doesn’t look like a hobo stove. I think with some creative plastering we can actually make it look quite nice. Pictures of the final product will have to wait- we won’t get this puppy in until the floors are done in the new house, but here’s some photos of the supplies to give you an idea of how it comes together. Simple and efficient.

 

A few basic measurements and calculations and we’re on our way.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cut a piece of stove pipe to extend the feed tube by 4 inches.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

That’ll be the J tube and riser.

 

 

 

 

 

 

 

 

The tin from an old water heater is perfect for cutting down and making a sleeve to hold the insulation around the riser.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cleaning out the barrel.

 

 

 

 

 

 

 

 

 

Testing the draw on the internal unit. It draws surprisingly well, thought it might not at this stage. Now all that’s left is to cut a hole for the chimney and put the whole thing together.


 

 

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The pocket rocket is a brilliant little invention that Ianto Evans and Larry Jacobs came up with some time in the late seventies, early eighties. (Yes, I did mention to Ianto that he might have thought of copyrighting that name before another, ahem, ‘invention’ made use of it. Hindsight, eh?) We built one for use in our sauna last year, to try out both earthbag building and rocket stoves at the same time. We went out in January to test how it would stand up to colder temperatures and within under ten minutes, we had raised the temperature from -15 C to +35 C, a 50 degree difference!

It requires only a few easily scavenged materials and is a great ‘starter project’. You’ll need a 30 or 55 gallon drum- one with a detachable clamp-on lid is great for a pocket rocket. And a couple of pieces of pipe- one for the feed tube and one for the chimney. That’s it. A little mortar for around the pipe and you’re ready to roll.

Start by burning off any paint on the barrel. We just stuck ours in our firepit and let it go for a while. While you’re waiting for the drum, cut two holes in the lid- one to fit each of the pipes. (Note: if you want to use the top of your stove for heating water, you’ll need to position those holes with enough room for a kettle or pot.) We didn’t cut our holes to the exact size of the pipe- we cut them slightly smaller and then cut tabs to fold up along the pipe for a nice snug fit.

When your barrel has cooled, dust off any remaining paint. Place your rocket stove somewhere away from anything flammable. (Seriously- this thing heats up like crazy!) Put the lid back onto the barrel and position your feed tube. It should be a few inches from the bottom of the barrel. Place your chimney in the other hole. The chimney (exhaust) only needs to go into the barrel a bit, several inches should do you.

The rocket stove prefers small diameter, straight wood. Gather some up and test drive! It’ll sound like a rocket when it fires up- that’s the draw. If it’s roaring when it starts- you’re good. Wait until it cools a bit and then mortar around the pipes. If you’re not getting the draw you want, fiddle with the feed tube a bit until you get it to just the right height. It may take a bit of patience, but this is a stove you can build in a matter of hours, so it’s worth playing around with to get just right.

Have fun- and let us know how it works out for you!

NOTE: If you want to preserve some of this heat, you could easily cob around the lower half or two thirds of the barrel. Otherwise, be prepared for some incredible radiant heat!

DISCLAIMER: This isn’t something you want to be building in your traditional home, as it would be a fire hazard.

Barrel for the rocket stove

top of barrel, with holes for connecting pipe

basic pocket rocket

pocket rocket fired up

A couple of rocket stove mock-ups

A basic pocket rocket used for interior heat

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We intend to go entirely off-grid. I can’t say exactly when we’ll hit that goal, or what the final system will look like quite yet. Redundancy is important to us so that if a component fails or is down for maintenance it’s not an entirely dire situation. So is efficiency. Ideally, we want the greatest return for the least input- particularly where fuel is concerned. We’re confident that the rocket mass heater we’re building to heat our main living space meets this criteria.

A rocket mass heater burns (wood) fuel extremely efficiently. Seriously efficiently– which is important to us for several reasons not the least of which is that we live on the prairie. There are lots of systems that make this claim but I have never seen anything like the rocket stove. When we were in Oregon, one of our projects was a rocket water heater. When we fired up the system to test it we were encouraged to go around to the exterior of the building and put our faces close to the exhaust. (I know, I know- apparently I’ll do anything for a lentil burger.) I was utterly amazed when instead of a face full of smoke, I was greeted by a cool steam. The wood was burning so efficiently, and the system using all of the heat, that there was nothing but a light steam by the time it reached the outdoors. This is the promise of a rocket mass heater.

That’s the other very important feature of the rocket mass heater- efficient use of heat. When you think of a traditional forced air system, or even a regular wood burning stove, it’s clear to see that a lot of heat is wasted. The mass heater, on the other hand, stores the heat for slow release in easy to build, dirt cheap furniture. Excuse the bad pun. The heat travels down a course built into the furniture (in our case, a combination couch/day bed) transferring its heat to the cob that encases it and slowly releasing it. Essentially, the chimney is inside of the furniture exiting only when it has had a sufficient run to use up the heat. For example, a standard 6” system would have a run of about 30’ and be enclosed in about 3 tons of material.

When you hear talk of rocket mass heaters, you’ll hear frequent mention of the combustion unit and the thermal battery. The combustion unit is roughly J-shaped, and is made up of the feed tube, the burn tunnel, and the heat riser. Measured precisely, and with good mortar and insulation, the combustion unit burns fuel very efficiently and draws well. The thermal battery, as mentioned, is in the furniture itself (or the floor, though it’s not a recommended first time project) in which the heat is stored.

It’s important not just to get the measurement of the combustion unit right, but to carefully consider the run. You don’t want to place the pipes too low into the furniture (or maybe you do, for a much slower bleed and perhaps warming the floor in front of the bench) but you don’t want to go to high and risk a burning hot surface. About 6” from the top of your bench is recommended for a nicely toasted bum. Your initial run will be the warmest, with every length doubled back running slightly cooler- assuming that you’re doubling your run (we may be tripling ours).

You’ll also want to insulate underneath the combustion unit and behind your bench (couch, daybed…) if it sits against a wall. No sense bleeding good heat into the wall. Vermiculite (industrial, not agricultural), perlite, or pumice are all good materials. Use your imagination but avoid anything that may off gas, like foams.

For all of this you’ll need only the most basic materials. Bricks (which you can reuse or make), clay soil, sand, straw, urbanite or rocks (for heat storage) and a couple of barrels and stove pipe, or metal duct. The size of your barrels will vary between 15 gallons for the feed tube, and 30-55 gallon for the heat exchanger- depending on your specific design. Most, if not all, of your supplies can be found and reused.

If I’ve made it sound complicated- it isn’t, but there is some patience and tinkering required. You can’t (or rather shouldn’t) just throw your system together and encase it in cob. You build the system, and fire it. Check it for leaks, or a weak draw, or any other issues, rework your design and fire it again until you have a leak-free system that draws well and burns efficiently. You’ll know it draws well because it actually sounds like a rocket. I’m sure I’ll eventually tire of the sound when it first catches but I’m still just amazed every time that I hear one start. You’ll also want to decide how much radiant heat you want as that will decide how much of the barrel to leave exposed. Myself, I’d like to boil water for tea on top of the heater, so I’ll need to position the heat riser to within 2” of the barrel to create a hot spot.

Once your design is perfected, you’re ready to encase the entire thing in cob and wait for your new furniture to set. (It’s a good idea to test it once again, before your furniture is rock hard.) If you’re a patient person, you’ll have a mass heater that will last you for years. If you try and rush this, you will regret it- it’s not as easy as throwing out an old couch.

Now, having said that it’s efficient and simple to build- I’m not going to go through the entire process on this blog, nor could I without writing a book-length piece. Pick up the actual book- “Rocket Mass Heaters” by Ianto Evans and Leslie Jackson- it’s well worth it. You can buy it in book stores but for the (small) profit to go directly to the authors, you can order it at http://www.cobcottage.com/products . The book will walk you through the main components of the system, layout, calculations and exact measurements. And, apart from the fact that you won’t be able to build a mass heater based on my brief overview, the book also provides alternative models and adaptations, including a rocket hot tub, a Guatemalan cook stove, and an ingenious little coffee rocket.

As a prelude to building a mass heater, try your hand at a pocket rocket- a very simple rocket stove. It is really easy to build and throws an amazing amount of heat, but most importantly it will get you started, build your confidence and have you well on your way of being as hooked on these wonderful heating systems as we are! I’ll provide full details and pictures so that you can build your own pocket rocket in my next blog.

The combustion unit of the water heater

The combustion unit of a mass heater

Note the clean-out

Super cozy rocket mass heater, Cob Cottage, OR

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