Katha Meyer

Thank you for that link, Jeremy! Very interesting!

I just looked up the conversion of ppm to g/m3. The formula is: concentration (ppm) = 24.45 x concentration (mg/m3) ÷ molecular weight. The molecular weight of CO is 28.01 g/mol. The conversion factor from mg/m3 to g/m3 is 1000.
So 1.25 g/m3 = 1250 mg/m3 = 1091.128 ppm

1091.128 ppm CO would be the limit value in Germany.
If my conversions are all correct the RMH in that test would not be meeting the german requirements. This in turn would mean that a modern Kachelofen is burning cleaner than this one tested RMH.

Are there more tests like this to get a bigger picture?

If I made any mistakes in the conversion, please correct me.

I found some more info on the legal requirements for a Kachelofen here in Germany:
- the efficiency has to be at least 80%
- up to 1.25 g/m3 of carbon monoxide allowed
- up to 0.04 g/m³ of particulate matter

Is there any data about this for Rocket Mass Heaters? Has anyone ever measured the carbon monoxide or particulate matter content for Rocket Mass Heaters?

Thanks for your answers!

Hi there,

I´ve done some research in the last few days about Rocket Mass Heaters and similar types of wood heaters. I am German and RMHs are not realy known here and it is hard to legally run them in your house.
But there is an old type of mass heater here, the Kachelofen, that seems very similar. Lots of old farmhouses still have them.

I am curious if anyone knows if Rocket Mass Heaters are still better than Kachelofen or in what situation they would make more sense. Which type of heater would be more efficient and why?

The main difference I see between the two is that the heat riser in a RMH seems to be taller than in a Kachelofen. Also a Kachelofen is made completely out of firebricks, there´s no metal barrel or pipes. The Kachelofen has a door that can be closed and the fuel feed is not open.
The fire in a Kachelofen burns at around 1000°C and the temperature of the gases leaving the chimney can be as low as 60°C, which is the minimum temperature required by law in Germany. Most people have the fire going for 1,5 hours. The thermal mass gives of heat for 12 to 24 hours (some ressources even say 30 hours).

Is there a big difference that I´m missing? Or are both heaters basically the same?




I am very curious to see what you guys think. Thank you.