Hello, welcome aboard and thanks for your feedback!

Yes, I've heard of Rocket Stoves and Mas Heaters. I've been experimenting with different kinds of make-shift Rocket Stove constructions for my summer kitchen, but I've always taken them down for the winter. I'm hoping that this summer I get to build a more permanent outdoor kitchen, based on my previous experiments. And, some year in the future I'd like to build a small greenhouse with a Rocket Mass Heater - but that is not an immediate plan at the moment, so at this point I'm not asking you to send that interesting PDF. For I already feel more or less over-burdened by the constant overflow of digital information, so I try to keep my daily life simple with only limited amount of information to process each day =)

Rocket Mass Heaters have some interesting features for small-scale DIY-builders. And the basic principle is pretty familiar for anyone who has grown up here in the north. For different versions of Mass Heaters have been used in Finland since the ancient times - you just need one to keep your house heated during the winter. With a quick search I couldn't find a diagram of the typical Finnish mass heater, but here is a wikipedia article of the model which was the most commonly used type in Finland for most of the 20th century, until those were gradually replaced by central heating systems or electric radiators. Although the wikipedia article doesn't contain a structural diagram, I'd guess by just looking at the picture one can imagine how the flues run up and down inside the tall structure. That design is said to capture about 80% of thermal energy of the burning fire. On normal conditions burning a cubic feet of dry firewood will keep the Pystyuuni warm for 24 hours or longer.