Need help with Rocket Mass Heater design that fits bureaucracy problems in Germany

Hi!
In Germany, several things make it almost impossible to build a rocket mass heater:

1) Any kind of fireplace is only legal if built by a licensed oven manufacturer. Or if you can find one that will license the one you built yourself (for insurance reasons), but that is much harder. I know of one that has not been in use for years because no one has ever licensed it.
2) Any kind of fireplace needs a chimney that will go over the crest of the roof. This is German law. sigh.

So my questions are:

1) Has anyone here ever heard of someone who successfully did this in Germany, legally? Or anyone who has successfully hidden it from authorities in Germany, which are... watchful?

2) Do you know an oven manufacturer that is licensed in Germany and knows how to build one?

3) Is there a design that could fit the crest issue? I thought of something like a huge pile of cob in a corner that reaches almost till the ceiling, where there is then the opening and the barrel. The heat from the barrel could be enough to get the exhaust out over the remaining meter, maybe? I am no engineer. I also don't know if putting the tubes in a downward spiral would actually work. Sigh.

So thankful for your advice. Wood prices have exploded since oil and gas have as well.  Would love to get going soon.

Hi Tomke;
When you live in a town with watchful authority and most likely nosy neighbors your only choice is to be sneaky...
Not that I'm encouraging you to ignore the law but sometimes that may be the only way you can accomplish your goals.
However, be prepared to accept the consequences if you are exposed...  

An existing chimney is the only way you might avoid notice by others.
If your home does not have an existing chimney then I'm afraid you will be noticed by many if you attempt to install one.
In the US, I have heard of folks living in high-rise buildings where RMHs have been built with a horizontal chimney.
The "Crest law" would not allow you to get away with that design, and there can be wind issues with a horizontal chimney.

A properly built RMH once it is running will have little to no smoke exiting the chimney.
Steam is very common from damp wood.  This simulates a clothes dryer vent and any discharge will dissipate quickly and will not smell like wood smoke.
If only the authority's understood that ALL wood burners need to be as efficient as an RMH.
Then their concerns about air pollution would be groundless.

I believe we have had folks in Germany with successful RMH builds but they were located out of town.

Yes, I have thought about that. It is also a rural area, so I am not so conceirned about neighbors. But a chimney sweeper is coming once a year for some check-ups downstairs in my mother's flat. They would notice immediately.
Is an existing chimney alright to use with a RMH? I have always thought that it is too long, so that the exhaust is not going up properly since it is too cold already. The chimney I have had before also needed to be heated permanently so that moisture would stay out of the wall. How would you go about transforming a chimney for a RMH?  I don't have one, just curious for future projects. I think there might be a horizontal chimney where there is currently a gas heater. Not sure. I am not living there fully yet.

Hi Tomke;
If your chimney is of adequate diameter  (15 cm or larger and in good repair).
And it is located inside your building rather than exposed to the outside temps.
You can utilize it with no problems.


The chimney sweep that comes to your moms, is he sweeping her chimney?
Is it a combined chimney with your home?
Are there other people using the chimney or is this a private residence?
Is a chimney inspection / cleaning an official requirement?

The bright side of this, IF inspections, are not required.
A properly built RMH burned properly will not have any creosote to clean.  You will not need a chimney sweep in the future!
Maybe Mom needs an RMH as well?

He is sweeping her gas heating exhaust. It is a house that has two flats, basically. One downstairs, one upstairs. Both have their own gas heating with - as far as I know - horizontal chimneys for their exhaust. I will be there from the 22nd, will have a long look at everything then. A regular chimney is not available there. But those two gas heaters should have one small horizontal chimney each. Mom said that the chimney sweeping is actually totally unnecessary, he comes because it is an official chimney which is used, but there is nothing to clean. He does it anyway, as he is required to. Gotta love Germany
But that means the gas heater exhaust is not required to go above crest, which is interesting. I'm sure this is not very clean or healthy to breathe.
Mom definitely needs a RMH as well, but she is very nervous about doing things illegally, hates the smell of burning wood and is a kid of the post-war generation that never wants to do more for heat than turn up the thermostat again. So inspections for at least the downstairs chimney seem non-negotiable right now. I will ask her if he ever comes inside - if not, maybe he can sweep away happily without knowing what IS coming out that upstairs horizontal chimney

Masonry heaters, Russian Heaters have been built in Germany for centuries, I would think a RMH
would be considered similar.

Here is something from 10 years ago
https://permies.com/t/19210/RMH-Germany

" Thing is: who checks your fireplace? the official chminey-sweeper (bezirks-schornstein-feger).
He has to approve of a fireplace. the law ("feuerstättenverordnung") seems not to be very specific on that.
It seems schornsteinfegers can approve of self-built stoves if they like and see these ovens as safe and environmentally friendly.
They might require that the project is done or supervised by a professional oven builder. there are lots of masonry-heaters in germany.
Each is somewhat unique. Maybe RHMs would fall into that category."