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Summary
part 2 of a 2 part podcast
Paul and Matt continue the J-tube vs batch-box debate
Paul invites Matt to counter the arguments against batch-boxes. Matt says that he doesn't really see a clear winner for efficiency between J-tube and batch-box. However one thing he sees is people who don't like the look of a J tube with a drum. Matt's mission therefore is to make batch-box builds more accessible. Summing up, the J-tube is probably more flexible in use especially for smaller spaces.
Paul now broaches the subject of efficiency when the fire is out. On a typical batch box, there's an open air vent in the door which, especially soon after burning, extracts air from the room and sends it up the exhaust. For a J tube, the answer is simple, you plug the feed after the burn, and to make a new fire you have to remove the plug. If you install some device to close the air vent in the door, it requires that people remember to open it again. They talk about various options. One option Matt refuses to entertain is a damper in the chimney, because having the chimney shut off at the wrong time is potentially much more dangerous.
They discuss the issues of starting and cold-plugs which Paul says is the Achilles heel of all RMHs. Paul declares he won't use a bypass due to the possibility of human error - he'd rather design the system so it doesn't need it. Matt mentions that on a cookstove design people want to be able to cook on it in summer, and that is also a use for the bypass.
They address a question about being unsure about building a batch-box. Matt argues that designs are out there, and you can start by dry stacking the bricks to get the feel of it. Paul repeats his assertion that you should start with a J-tube due to its simplicity.
Relevant Threads
Rocket Mass Heater Smackdown: J-Tube vs. Batch Box
History and development of Matt Walker's rocket mass heaters
Rocket Mass Heaters forum
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Banter Couch
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