todd Reed

Hi Matt,

Okay, thanks. That's helpful. I may well do what you suggest and build one outside to see how it goes.

Hi all,

I've been thinking about putting a rocket mass heater in my surburban house and for a variety of reasons I think that's not really practical at least on the inside

However, doing a pilot project outside my house is quite possible.

So I'm looking at a brick planter outside the back south-facing wall of my home. It's on a patio with protection from rain (Sun-tuff) so exposed to lots of ventilation.

The planter is around 30" wide, 30" tall, currently filled with dirt. There's also a gravel area nearby that could hold the heater.

The planter and the ground nearby is next to a basement crawlspace opening where I could tie into the ventilation system.

So, here's my idea. If I put in a RMS with thermal mass and some form of heat exchanger buried in the RMS, it would be possible to circulate the warm air generated by the RMS through the ventilation system.

I could do this as a relatively low-investment project that doesn't involve renovating the interior. I could move air through the RMH with a small blower outside the building envelope tieing into the existing vent system. I have an existing pellet stove that only heats the front rooms. With the RMH running potentially I could warm up the back rooms as well.

Questions I have: is this practical to do? What kind of heat exchanger would work? Galvanized pipe, duct work? Is it likely I can generate enough heat this way to move it into a vent system and get a useful result?

Even if it doesn't work as an external heat system, it's worth doing just for the experience of setting one up. Is a brick-lined planter a good way to do this? Barrier system against heat loss through the ground?

Thanks for any tips here.

My two cents for what it's worth. I'm a surburban home owner, full time employed. I've looked at rocket mass heaters on several occasions. I iwill call that going down the rabbit hole, following a topic of interest. For me that means watching video clips, reading about the technology, getting an idea of what's possible.
So, in going down the rabbit hole what I see is a lot of hobbyists building stuff with skills I don't have. Cutting and welding metal, doing cob structures in a house, experimenting and iterating stoves until they get a working model.
I can see the potential of rocket mass heaters. I have a pellet stove I found on craig's list for $250 in excellent condition that I installed myself including double wall tubing through the wall of my house.
I mention this because this pellet stove is a known technology. The steps involved are very predictable and I have heat in my house for 3 seasons now in a way I can support, fix, run and operate successfully.
My insurance company is happy with my stove, so is my wife. So is the guy I had come by to inspect it to make sure I didn't screw the pooch somehow.
When I look at rocket mass heaters I end up looking at these constructs that are beautiful in terms of the end result but quite messy in terms of the build. Masses of rock or thermal material in a box, a 55 gallon drum, cob and so forth. Do I want to take the risk of purchasing or building a RMS that doesn't work or perform as expected?
The only way I see an RMS in my future is if I set up a long term project to iterate through builds of a rocket stove until I feel confident enough to trust building one in my house. That's an investment of time and attention with a lot of scattered resources, skill building, and costs that when all is said and done...fire up the pellet stove, winter is on the way.
So, if I had a suggestion for getting people to build RMS's...put a course on Udemy or Skillshare teaching how to do this step by step. Course 1 - basic heater, course 2 - more advanced version....and so forth.