Rocket mass heaters and basements

I would love to install a similar RMH in my home.

I watched the installation video of this unit.  Does the house this is installed in have a basement?  Could a mass heater be installed in a house that has a basement or would the weight be too much to support on the first floor?  Would there be a safe and logical way around the weight issue if it really is one?

Tyson Wolfe wrote:I watched the installation video of this unit.  Does the house this is installed in have a basement?  

I think you must have watched something else.   The video of this installation shows the support we put under the floor.   You can get the 4-DVD set which includes this insall here.

Tyson Wolfe wrote:I would love to install a similar RMH in my home.

I watched the installation video of this unit.  Does the house this is installed in have a basement?  Could a mass heater be installed in a house that has a basement or would the weight be too much to support on the first floor?  Would there be a safe and logical way around the weight issue if it really is one?

Since heat rises; I wonder if a rocket mass heater would be even more efficient if the stove was built in the basement. Could the floor itself serve as a secondary mass?  There may be an obvious reason why this wouldn't work. Building basements in my area would require dynamite so they're an architectural unicorn to me.

The basement is generally not a good place for an RMH, for a number of reasons. Hot air is not the principal output, and you would be heating the basement far more than upper floors.

A typical RMH weighs one to several tons, and would generally need more than just floor joists; the amount of extra support required depends on the individual situation.

Casie Becker wrote:

Tyson Wolfe wrote:I would love to install a similar RMH in my home.

I watched the installation video of this unit.  Does the house this is installed in have a basement?  Could a mass heater be installed in a house that has a basement or would the weight be too much to support on the first floor?  Would there be a safe and logical way around the weight issue if it really is one?

Since heat rises; I wonder if a rocket mass heater would be even more efficient if the stove was built in the basement. Could the floor itself serve as a secondary mass?  There may be an obvious reason why this wouldn't work. Building basements in my area would require dynamite so they're an architectural unicorn to me.

My understanding is that heat does not rise.  Hot air rises.  But heat transfer from a rocket mass heater occurs in two other ways besides convection (heat transfer with warm air).  1.  Radiant heat, which radiates in all directions, not just up.  

2.  Conduction.  Direct heat transfer by a cold object (say...Paul's feet, or his bum) directly touching a warmer object, like the mass of a RMH)  Also, conduction happens in any and all directions, not just up.


That's why a basement installation is a poor choice for a RMH.  You waste the number one and number two most efficient heat transfer mechanisms.  Convection (heat transfer by hot air) is the least efficient of the 3 methods.

Troy Rhodes wrote:

Casie Becker wrote:

Tyson Wolfe wrote:I would love to install a similar RMH in my home.


That's why a basement installation is a poor choice for a RMH.  You waste the number one and number two most efficient heat transfer mechanisms.  Convection (heat transfer by hot air) is the least efficient of the 3 methods.

I'm going to be the language police here and say that "efficient" isn't the right word here.  Conduction and radiation are more effective heat transfer methods for heating our bodies directly, or an immediate airspace.  In this way, a RMH might be a fairly effective way to heat an old, drafty, single room building such as a barn, or even an open air area.  However, I can imagine a type of mass that would both store the heat output pulse of the rocket stove well, and still transfer effectively via natural convection; we would just have to design that feature in deliberately.  To some degree, we have this with the heat riser barrel; since a certain amount of rapid heat loss is required to build up the draft anyway.  Perhaps we could improve the natural convection of the stored heat by using copper rods embedded into the mass & directly connected to a metal surface, but not directly attached to the mass's vent pipe.  In such a way that the heat must conduct through much of the mass before conducting into the copper.  Another way would be to build openly vented water tanks embedded into the mass, but also not directly connected to the vent pipes, so that stored heat can also release via water vapor convection; but the disadvantage there is that those tanks would have to be refilled manually on a regular basis.

In my understanding of the thermodynamics, if the goal is to heat people with the minimum amount of fuel, then conduction and radiation are, in fact, the most efficient.

There are numerous other ways to define the problem where your use of the word effective would be more appropriate and accurate.



But again, we are left with the conclusion that for most residential applications, it is neither advantageous nor desirable to have a rocket mass heater in the basement, unless you live in the basement with the rocket mass heater.

If your insulation in the home and basement is really good, you might do well with a max-extraction rocket stove.

Use a double barrel, perhaps with some additional radiators prior to exhaust [maybe a bell or two, sans the mass] to pull as close to all of the heat out of the air as practical [whilst still having enough heat to push the air up and out the chimney] before sending the air out of the system.

Couple this with whatever mass you *can* incorporate into the main floor. Fish tanks, stone tiles, earthen furniture... arrange it all as best you can, your aim is a few tons of mass up there to absorb the heat coming up from the basement so it doesn't fly out of the house every time somebody opens a window or a door.

I have not read all the other threads here about rocket mass heaters in basements, but I do know that ernie and erica generally discourage it.    There are two massive negatives.  

downside number 1: (already mentioned)  to take advantage of radiant and conductive heat, you have to be in the same room as the rocket mass heater.  People building a rocket mass heater in the basement tend to be thinking of a furnace - which functions in a very different way.

downside number 2:  If you have two stories, then your whole house will be acting as a sort of chimney - and it will (sorta-kinda) suck on the wood feed to make the rmh run backwards.  UNLESS you run your exhaust from the basement, through the roof of the whole house ending above the highest point on the roof.  



Mostly, I strongly encourage you all to read all the other threads we have here about putting a rocket mass heater in a basement.

Downside number three: Aside from needing to be in the same room to benefit best from a RMH, you also need to be spending most of the burning time in or near the same room, so you can easily tend and feed it as it needs attention. If you don't regularly spend some hours a day in the basement, this will be a problem. The exception to this would be a batch box, which is intended to start, fill, and walk away for an hour while the whole load burns.