Batch Box Rocket Mass Heater with Peter van den Berg by paul wheaton   1 year ago


472 Likes   25 Dislikes Peter van den Berg joins the rocket mass heater jamboree from The Netherlands. He thinks of himself as a tinker of wood burning and divides rocket mass heaters into "the front end" where the burning happens and "the back end" where the heat is harvested. He thinks of himself as a "front end man". Peter is well respected in the rocket mass heater community as "the numbers guy" - he very carefully measures everything!

In this video, Peter gives us a tour of his 8 inch batch box system that he built in 2014. At the time, this was the largest batch box system he had ever built. He started by building a mock up with Matt Walker. Things looked so promising, that he decided to make it his project for that year's rocket mass heater innovator's event.

The advantage of a batch box rocket mass heater (over the more traditional J-tube design) is that you can burn a lot more wood all at once.

Since this one is in a shop, Peter decided to harvest more heat immediately and put less into the mass. The idea is that a mass is good for a home where people will be there every day. But a shop might have people in it sporadically, so you need fast heat and you don't need to try to keep the space warm overnight or for the next few days because there is a good chance there won't be anybody there.

So peter implements a triple barrel design for fast heat harvest. And the barrels act as stratification chambers. Very little heat gets into the bench mass.

Peter does a broad range of testing on all of his stoves. For this build, he tested the temperatures coming off the barrels and he tested the exhaust temperatures. He also did a lot of work testing the exhaust gasses.

He points out that a good stove puts out 3000 ppm of CO (carbon monoxide). And for a lot of this burn he was getting about zero ppm of CO. He shares the graph of one of the tests.

The thermal mass bench is a pebble style mass: a wood box with a duct placed inside then filled with pea gravel and topped with bricks. As he is sitting on it he is commenting that it is quite warm. So warm that he prefers to sit on the pad which is on the bench - sitting on the bench directly is too hot!

The full build of this rocket mass heaters is on our DVD set at

Thanks to Dan Ohmann of The Grass-fed Homestead channel for helping me with the editing:

Relevant stuff at permies:

music by Jimmy Pardo

Thanks to my patreon peeps for pushing me into making videos again:

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