Are rocket mass heaters safe?

From what I can tell, the wood is loaded vertically and sticking up out of the part it goes in. We have cats that would see the wood sticking out and mess with it.

There are so many benefits using RMH but is there a way to build one where the cats would not be able to mess with the wood or stick their paws into any part of the heater? Could we attach a door somehow over where the wood is loaded?

Hi Felicia:  My feed tube is 16" deep , most of my wood is several inches less than that . We raise persian kittys so I know all about cats getting into trouble. Our RMH is not in the house where the cats are but a regular heavy wood burner is. We call it the kitty warmer ... they all know where and what it is and in almost 20 years of breeding we have never had a cat or a kitten burn themselves on the hot metal. They understand HOT very well.  As far as a J tube RMH if your wood is not sticking up they will not mess with it . The throat of a feed tube is HOT and your cats will know it. However they will claim the mass as their new home! If you are still concerned, then consider building a batch box RMH , they have a door.  

thomas rubino wrote:Hi Felicia:  My feed tube is 16" deep , most of my wood is several inches less than that . We raise persian kittys so I know all about cats getting into trouble. Our RMH is not in the house where the cats are but a regular heavy wood burner is. We call it the kitty warmer ... they all know where and what it is and in almost 20 years of breeding we have never had a cat or a kitten burn themselves on the hot metal. They understand HOT very well.  As far as a J tube RMH if your wood is not sticking up they will not mess with it . The throat of a feed tube is HOT and your cats will know it. However they will claim the mass as their new home! If you are still concerned, then consider building a batch box RMH , they have a door.  

Thank you! Ours will definitely need a door just to help us feel more at ease. Is there a book you know of that explains how to build a batch box version?

Also, I read that an RMH is able to cool the space it's in during the summer due to the thermal mass of the cob/plaster on it. Is this true?

Well, to start you should have a copy of the builders guide ( the builders bible) . It has a small section on batch boxes . It also has all the basic info you need to build and design your mass , utilizing bells.  More detailed info on a batch box build is available here at permies or over at the donkey pro board.

If its not in the sun, then yes it will be a cool spot... but don't expect too much if you live with high humidity.

We live in Alabama. Very high humidity. I've been trying to research a non electric, natural way to cool the straw bale shed we're going to build. It'll be 200 sq ft. And where we're building it will be about 50% sun and 50% shade.

Is this the guide you're referring to? I have it in my cart to order tomorrow.

Yup that's it!   Read it cover to cover.

Will do!! And thanks!

Consider a home made swamp cooler... would need a solar panel to run a water pump and fan but they definitely help here in the dry hot inland north west.  Not sure that it would be as good in that absolutely horrible humidity but not much involved to build one and it can't make it any hotter!

Thanks for the suggestion! I'll research it more😁

On a side note.. do you happen to know how to determine the slope for a roof?

Rise over reach,  On a 24' building If your ridge pole is 6' high and reaches 12' from center to the outside wall you have a 6x12 pitch roof.   If ridge pole is only 4' then you have a 4x12 pitch,  a 12' ridge and you have 12x12 pitch roof.

So, if we'd like an overall wall height of 6' at the front and for it to have a simple shed roof like a lean to sloping towards the back of the building, would it be enough of a slope to have the front wall be 6' and the back be 5' or no? Guess I'm just confused about how much of a slope is acceptable. Read somewhere that it's a 1/4" rise per foot of wall height but then read elsewhere that you multiply whatever pitch you want (3/12 for example) by the total width of your building. If my building is 10' wide that would be a 30" rise; 2.5'. So, if we want a 6' high front wall, does that mean that we only build the back wall up to 3.5 feet and make the front wall 6' tall to give the roof a 2.5 foot slope? Hopefully that makes sense.

Well only if you are 3.5' tall... lol   Rear wall is the set height . Your in Alabama, how much snow do you get??? I would think you can pitch your roof however steep you like.   front wall 8.5' tall rear wall 6' or make it tall front 12' then down to 6' in the rear , put in a 6' ceiling and use the upper area as storage.

thomas rubino wrote:Well only if you are 3.5' tall... lol   Rear wall is the set height . Your in Alabama, how much snow do you get??? I would think you can pitch your roof however steep you like.   front wall 8.5' tall rear wall 6' or make it tall front 12' then down to 6' in the rear , put in a 6' ceiling and use the upper area as storage.

lol that makes sense😆 We get about 1.6" of annual snowfall.

Felicia Adaniels wrote:

thomas rubino wrote:Well only if you are 3.5' tall... lol   Rear wall is the set height . Your in Alabama, how much snow do you get??? I would think you can pitch your roof however steep you like.   front wall 8.5' tall rear wall 6' or make it tall front 12' then down to 6' in the rear , put in a 6' ceiling and use the upper area as storage.

lol that makes sense😆 We get about 1.6" of annual snowfall.

 Make sure you choose a roof type that is compatible with such a low slope... Many roof types require a significant pitch.  Asphalt shingles require a 2-1/2 foot rise per 12 foot run.  So either choose your minimum roof slope by the type of roofing you want to use, or choose a type of roofing for low slopes if you go with a lower pitch.

Higher pitches shed rain, snow,
and debris better... Rain and forest debris being the most serious concerns where I am in the wet and windy PNW.

Felicia Adaniels wrote:

Thank you! Ours will definitely need a door just to help us feel more at ease. Is there a book you know of that explains how to build a batch box version?

Have a look at this link Felicia - Batchrocket Resource

It is full of useful information on how to build a batch box.

To reply directly to the OP's question, it depends, as with everything, on design and execution. But theoretically, because the hot bits are encased in masonry or cob, and because those things don't burn, yes.

As to cooling your shed, you might like to have a look at the BBC Tudor farming series.

https://permies.com/t/59205/Tudor-Monastery-Farms-video-series#503267

If you're not as enthralled as I was, that's okay, but they describe and show an example of how they'd design their outbuildings to cool themselves at need. The key was in the flooring and a deliberate cross-breeze. I believe they said the flooring was unfired clay, which absorbed and regulated moisture. When they wet down the floors, though, and opened windows or doors on either end, the increased draught would evaporate the moisture from the clay, the phase change causing a drop in temperature. It's the same principle as keeping a large jug or vat of unfired pottery containing water in it in a hot climate, sometimes with a cloth wicking moisture from the reservoir to the outside of the container, the evaporating water cooling the interior space.

-CK

thomas rubino wrote:Consider a home made swamp cooler... would need a solar panel to run a water pump and fan but they definitely help here in the dry hot inland north west.  Not sure that it would be as good in that absolutely horrible humidity but not much involved to build one and it can't make it any hotter!

could you direct me to any information on homemade swamp coolers?