I love rocket stoves and mass heaters and have been recommending them for years. However, there are limitations to everything. Here’s a report from frigid Canada where a rocket mass heater wouldn’t work.
“Our adventure in natural building and sustainable living has hit a major hurdle. A big part of our plan was the Rocket Mass Heater. It really seemed like a good idea at the time. And I really wanted it to work. I wanted so bad to love it. Never got there. I built a few mockups and rebuilt the final one twice. I read everything I could find on the subject, ran all kinds of experiments and even traveled to Oregon to meet the folks who are the most experienced experts in the world on the subject, including the original inventor.
Things worked great if conditions were right, but wind is certainly an issue and we get plenty of that here. In order to get a decent draw I had to have a tall chimney out side. That means a heavy column of cold air is pushing down into the system. Since a RMH isn’t sealed, cold air blows through the system and into the house making it very difficult to get a fire started. I tried warming the pipe with bricks from the cook stove, candles, and even a torch. Putting a duct fan inline at the top of the chimney helped for a couple days, but once the system got hot, it burned out. Getting it going in very cold windy weather always had the risk of having smoke blow back into the house. Not good, remember that ‘look’ I mentioned? Besides, even when the damn thing was burning great, with that cool rocket sound, I’d have to feed it every 3-1/2 minutes. My wife and I talked about all kinds of modifications but in the end we’d never be able to make it work in our situation and environment. You can put wheels on a horse and shove an engine up it’s ass and you still won’t be able to take it out on the highway. So goodbye rocket crap heater and hello Blazeking Princess wood stove.”