Rocket Stove Mass Heater / Consealment

Hello,

five years ago I had build a first Rocket Stove Mass Heater.

Now it is time for my second attempt.

I want to build a masonry type that has to heat a rather small but not well insulated brick build garten house of about 200 sqaure foot.

The challenge here is, that I am not allowed to build a stove here and have to conseal the chimney/exhaust.
Most people will not object to a stove in such a garden as many have them and will not say anything, if I build one. Expecially not during energy crisis here in Europe. But it will be much easier if only few or no other people realize, that there is a newly build oven.

The smell is not so much a problem, as there is smell of wood burn from one of the houses near already. And probably much more once it gets cold.

My idea was use a bench design with piping and then let the cooled exhaust out directly through the wall to my very small shed 12 square feet or so, where it could stratify to the roof and then go out via the large opening over the top of the door, once it cools down. It is well ventilated and probably no hazzard for anyone, because it is very well ventilated and very small. Even if anyone would breath too much CO2 and fall down, he could only fall into the open and fresh air...

I guess 6 inch design is enough heat for that house.

What do you think?

Hi Martin;
You're thinking outside the box here, Good Job!
I assume both buildings are side by side or nearly so?
A 6" J tube rocket can push 35' of horizontal piping to reach inside your little shed and go vertical. The Vertical portion does not count.
Having already built a rocket you understand that during startup it will indeed produce smoke.
I suspect your neighbors will figure this out before too long but as long as the "officials" do not take notice you should be fine.

Martin,
RMHs really need to have a vertical exhaust to provide the necessary draft to not get constant spats of smokeback. Through-the-wall installations with no vertical piping have been done (been there, done that) with limited success but I wouldn’t recommend them.
Some smoke at startup and at the end are quite normal but for the most part, heat shimmers is all that a properly working RMH should produce.
Reliable draft then becomes much more important in the long run than trying to conceal a few minutes of smoke here and there.

Since your building is made of brick, maybe you could build a brick "tower" with decorative crenelations. "It's not a chimney, it's a decorative tower." Dunno if it would work, and it could be expensive in terms of time and bricks.

You might not get much smoke out of the chimney but, you might get a lot of water vapor giving the impression of smoke!

Thank you all for your replies.

Conserning a chimney: Instead of going to my shed, I could go through the walls to my veranda, that has a roof and build a chimney of roughly six feet under the roof. The roof is angled and well ventilated. But I think of making it a bid like a earthship by capturing heat with inclosing it like a greenhouse.

But I tend to prefer the shed idea: If it does not work at all, I can make an upward pipe through the roof and make it a chimney. But I would rather try it out consealed first. I could put a 90 degree angle and some pipe upwards at the end in the shed and install some kind of heating or fan to support the start up of the system and induce more draft.

It is one building, but the shed is seperate with its own door. I assume it was added later. Pipe goes directly through no more than two layers of brick.

I am also thinking about instead of having a bench with an doubleyou shaped pipe going through to position the oven in the center of the hut and have only a straight pipe of about 10 feet go straigt or just slightlgy elevated to the wall. That would be covered by the mass but probably be just about half the size of a bench but through the room or even a little bid less. That way the oven is central, close to the door which makes it easier to bring in wood, the heat will be more evenly generated inside and it may take a little bid less space over all. Or at least give me better use able options.

I probabbly will use a bid less mass around the piping this time and specially insulate (perlite clay sand mix) the burn chamber around the bricks better to have a good burn and less time heating the chamber.

Even a 6' vertical chimney in your shed, especially if it is insulated, may very well be adequate for draft. To give it the best chance, I agree with ditching the zigzag ducting in bench, but I would make a small bell. A hollow chamber in the bench will allow more heat extraction and give less friction. You could even make some sort of bypass at the end of the bench so that in the beginning of the fire the gases run straight along the top of the cavity, and once it is burning well, the exit is moved to the bottom of the cavity for best heat exchange.

For safety, I would put some sheetmetal above the chimney spaced an inch or so down from the shed roof framing to keep hot gases from hitting wood. It may not be anywhere near hot enough to start a fire immediately, but long exposure to moderate heat can slowly degrade wood so it starts burning at a much lower temperature.

While Iam  waiting for the rest of the materials, I have allready been working on the roof of the shed. First I have filled all gaps with mortar and now I will use aluminum below to cover the wood. Also I will install a sheet of metal at the roof overhang outside over the door. There should be nothing burnable exposed to high temperatures.

And better do a bid too much then trust in good fortune.
Also I will install a thermometer at the top of the shed that to monitor the temperatur from inside the hut, so that I can spot problems in time.

Just to see how hot it will get.

I guess the whole build will cost me around 200-250 Euro. But I had a large supply of old bricks (80years or so).
The expensive part is the piping expecially the one(s) with the opening for the clean out.

I am using 6.1' (160mm) diameter.

If you have a good supply of bricks, you really don't need any metal duct inside the mass, only for the final chimney. Just make the bench a hollow brick box of whatever shape you want, with the hot gases entering from the combustion core and the cooled gases exiting from the floor at the other end.

After some hard work the heater finally is functionally finished. It could use some more cob work, but other than that it was good to test:

And here is what I got after 3 hours of burn:

After starting up and convincing it which direction to draw it worked. But as you predicted it had backsmokes. And that is not what you want to have in a heater in a closed room.

I checked the smoke: It had almost no heat at all after leaving the pipe. It did not stratify up and cool down and get out but it got out right away.

The roof of the room after 3 hours of burn was not hot at all but had some vaporized water.

I put a lot of care into insolating the burn chamber and make it perform as good as possible.
The mass worked as it should. It took long to heat, but when I stopped heating the heat stored got up and warmed it up even more than during the burn.

I will get an elbow (90degree angle) and install one meter of pipe in the shed to see if it improves the draw. Also when I test it then I will run it long enough to dry a bid more.

At the moment the mass and the dryout process takes all the heat necessary for a good draw.
Maybe the elbow and pipe, drying will give the bid of draw necessary.

Or I need to go through the roof and install it a real chimney.

As it is, it is not really consealed. Anyone who has looked at me working or may see the smoke comming out of the room, will know what happens. Maybe a chimney is even more concealed, Because smoke from a door or a window could make someone call up the fire department...

I will keep you informed...

I considered your problem with how to conceal a stovepipe on your shed roof.  Then I thought about hiding it behind a couple of solar panels.  

Ok, people thought I was burning something in my garden. This could bring some trouble - at least if they think I do this often...

I probably will just install the chimney and wait what is going to happen.
A neighbor said, that probably nobody will object against an oven and a chimney. But I am not sure.

All the consealment for the chimney I will do, is to paint it black like the roof.

In some other garden colony all this would not be much of a problem... But here I am in a wealthy neigborhood with people with houses having leased a lot of the gardens neigboring their houses.

In less wealthy areas it is quite common, that people upgrade their gardens to live there at least during the summer and some all year long. Even though all this does not conform to the law those garden communities are based on.

On the other hand it is quite nice to be in a wealthy part of the city because people are so much more relaxed and overall nice on streets.
And it is far more quiet there. And I am living there for almost nothing at all... And my garden is perfectly sized for only one person.

You can never have everything.

It took a while, but now the project is finished (except for making the cob look nicer on the stove).

I installed a 11 or 12 feet chimney and it works very well now.
Got it to a maximum of over 500degrees Farenheit or 260 degrees celsius at the barrel top (mostly running about half as hot). The burnchamber got really hot inside. And the perlite insulation worked. On the outside there was almost no heat at all.

Next project is installing my solar on the roof.
I may or may not post a few fotos.

Thanks for everyone contributing.

Construct your stove with an implement to "heat food", such as a top plate or bread warmer.  There plenty of smokers, BBQs, hot plates, and pizza ovens out there... just make it look like one of those.  Put a stack of paper plates (fire starters), salt, pepper, plastic forks, and a few empty beer cans nearby... (I read somewhere here that food prep equipment are not room heating furnaces).  You could invite your neighbor over for bratwurst.

So it took just 3 days for the first of the rich to complain and call up the garden community chief.

It is so sad... But I kind a knew that this would happen. They have nothing else to worry about.
And I can not do much, because I have no right to have such an oven in the hell of German regulations.

Anyway the build was far better than my first one.

Luckily I got some money in the meantime and can start a new project somewhere else in the spring.