The Walden Effect: Farming, simple living, permaculture, and invention.

Rocket Stove Mass Heater vs Jotul F 602

Rocket Mass heater infographic

We like Roland's suggestion about building a Rocket Stove Mass Heater.

It seems like a clever way to get more heat from less firewood.

Maybe we would give it more consideration if we had not fell in love with our Jotul wood stove. Plus the Jotul F 602 serves double duty as "Fire Therapy" where the Rocket Mass Heater feels more like a chore to operate properly.

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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This question is about a different wood stove that you made. I read that you had an outside wood stove that blew hot air into your trailer. I read that it was a special kind of wood stove with an airpocket in it. What is this type of store e called where did you find a stove like that? I wanna do the same setup with my trailer.
Comment by Amanda Sullivan Sun Sep 30 07:50:46 2018
We've got a Jotul - I think it's the F8 TD - and we love it too. Our heating season is pretty short here, and we mostly only light the fire in the evenings, so it's not really worth it to muck around with rocket mass heaters. Plus we like to toast marshmallows and cook doughboys over the coals :-).
Comment by Darren (Green Change) Sun Sep 30 08:44:06 2018

Well, you don't have to give up fire therapy if you go for a "Grundofen". That's the German name for it, they're also popular in scandinavia. The proper term in English is masonry heater.

Here is a link to a video that shows how it is built. The comments are in German, but don't let that deter you. As you can see it still has the fire door where you can see the flames.

These heaters are very good at storing heat and releasing it slowly. They are heavy, of course. So building one in a manufactured home should involve looking at the load limits of the construction.

Comment by Roland_Smith Sun Sep 30 13:04:23 2018

My Mom found that air pocket wood stove on ebay.

It was home made and very weak compared to a stove like the Jotul.

Comment by mark Mon Oct 1 09:33:02 2018

@Amanda Sullivan

Forced air wood furnaces are available. See e.g. here. They're quite expensive. And the ducts that you need are pretty large. The ducts also need a significant amount of insulation, because air cannot hold a lot of heat.

I have my doubts about the efficiency of these things. The supplier I linked to seems to make them mainly because they don't have to meet the 2015 EPA standards for hydronic (water-heating) outdoor furnaces. To me, "buy this because it doesn't have to meet standards" is not a good sales argument.

If you are on a tight budget, just put a (modern) woodstove inside. At least that will allow you to capture all the heat generated. And a modern woodstove (with an "afterburner") will be pretty efficient and won't generate a lot of smoke and soot. To be fair, a wood stove in the house will cause more particulate matter ("PM") pollution inside than an outside furnace. (The sources of PM pollution can be unintuitive, though. When I was measuring PM pollution inside my house with a cheap Adafruit sensor, the highest value was reached when I opened the window; probably caused by a nearby busy road. There was also a noticable spike when I was cooking dinner on natural gas.)

If you can afford it, go for a modern computer controlled hydronic outdoor furnace, and put in underfloor water heating.

Comment by Roland_Smith Mon Oct 1 15:00:29 2018

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