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A few quick questions about design of a rocket mass stove

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Here are some quick questions to help me in the design of a rocket mass stove to heat my home. See what you can contribute:

1. Is there a simple way to draw in outside air for combustion at the point of intake [thus, eliminating negative air pressure in the home], either by pipe/duct work for combustion air at the place where the sticks are inserted?

2. is there a way to measure the heat output or to calculate the size of the chamber, piping diameter and volume of the mass area needed to adequately heat the area intended and function properly?

3. Can one or more glass blocks be used in the design to view the combustion area, for lighting/viewing purposes?

4. Can an existing roof exhaust vent stack be used to vent the gasses/steam, or would it be advisable to directly exhaust it out through a vertical wall, immediately from the 'mass'?

5. Besides cobb, is there any other material[s] that can be used to create a decorative bench, without detracting from the thermal properties and effectiveness of radiated heat by the thermal mass? Like stone or marble tile, plaster to create a sculpted or pillar effect.

6. Can you interweave copper piping [1/2"or 3/4"] in the area of the thermal mass or stove/combustion area [unexposed-for esthetic reasons] to heat water to assist in radiated heating [I have an existing boiler with zoned radiator baseboard heat], or to assist in hot water heat for my existing tank?

7. Lastly, any thoughts on having which would be easier for maintenance/clean out without compromising safety: a steel barrel with a removable lid [secured with a steel bold and metal ring] or simply a solid steel barrel?


~Mark B
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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- disclaimer, I don't git a nickel out of my advice from any one ! Mark, Start by going to and order Ianto Evans' great book 'Rocket Mass Heaters' - instantly download a pdf copy for $15.00u.s., or paperback for $18.00u.s., no other book has as much information in one place, NONE !

if you turn on the fan over your kitchen stove do you have to open a window ! (if you don't know, ask the cook!) If not, your house just isnt as tight as you think it is !
Heat 'Trapped' in the Rocket stoves 'make-up air' is carried to the thermal mass where it is taken up for conduction/convection back out to the room !
Measure the Cross Sectional Area Of the Heat Risers interior opening and keep the C.S.A. constant and wholly through out the build
Glass blocks will let light through but not translucently, lousy viewing
Yes, kinda, how is it made, any piping through interior walls, where and how does it exit the house ? Do not try to combine heating units chimneys into one vertical chimney !
The more Rock,Iron ore, Urbanite you add to your cob the more better it can take-up the horizontal chimneys heat energy.
You not only need a coil at the thermal bench but one to circulate the water into a holding tank somewhere along your return lines to the boiler, if the temp of your thermal mass tempered water drops below the temperature of your return lines, you have a net radiator not a device to raise the temperature of the holding tank this would require a thermistor to measure the lower temp of the holding tank,and turn on a pump for circulation.
Same with the lines run near your 55 gal drum, however a closed system opens you up to the accidental creation of an expanding steam explosion, the squish/bang event, not a good outcome !
A steel barrel with removable lid, you will also have a clean out immediately below the barrel where most wood ash will gather, it also allows inspection of the 1st part of your horizontal chimney !

g'LUCK , - PYRO -maticly yours Allen L.
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