Julie Reed

Glenn Herbert wrote: I would take some issue with the idea that RMHs have higher combustion temperatures than masonry heaters. If that is the case in any particular comparison, I would venture to say that the masonry heater is getting less complete combustion and possibly generating more creosote leading to some risk of chimney fires.

I was under the impression that an RMH burns much hotter, thus the need for specific material (ceramic or clay) burn chambers?
I haven't seen many masonry stoves (Russian fireplace style) but they all were just a firebrick lined box. The RMH burns off more of the gasses from combustion, but I think even with a masonry stove or efficient woodstove you are burning hot enough and complete enough that there's not much creosote, as long as chimney temps are adequate and the chimney/pipe is insulated. Given the design, I can't imagine a chimney fire in a masonry stove.
Interestingly, the concern about barrels, at least in the conversation we had, was not about the hot surface or clearances, but the (non) thickness of the metal, and how easily it can burn through.

Lots of info here, with source references- https://en.wikipedia.org/wiki/Brown_sugar.

Seems the sugar industry started the move away from true brown sugar over a hundred years ago, but the stuff sprayed with molasses is still the same stuff from the 1950s, essentially (at least in the USA). I do remember as a young kid, 'helping' (causing mayhem no doubt) my grandmother make cookies and asking her what brown sugar was, and she told me it was just white sugar and molasses, and that would have been late 60s.

But he didn't say that masonry heaters are illegal.   Just that a rocket mass heater isn't necessarily a masonry heater.  But I would think it would count as one.

Interestingly, we just had this very discussion, not with a code official but with an insurance company. They view RMHs as a different risk due to the combustion process of the RMH being drastically hotter. We also learned that they treat an RMH with a steel barrel as a ‘barrel stove’ which is not insurable. Apparently they are getting enough inquiries about RMH that there is some familiarity, which is good. The phrase ‘accelerated combustion’ was used. I’m guessing ’rocket’ is a really uncomfortable word to insurance folk! An open feed tube is also unacceptable, so it sounds like an all brick/stone batch box may be the possibility most likely to pass as a ‘masonry heater’, if progress is to be made with underwriting. A UL listing is still the ultimate hurdle for any heating device, unless built by a licensed insured professional mason.

 a bennett wrote:
But doesn't enclosing the stove make the metal too hot and might crack it?

This is definitely a valid concern. Woodstoves are designed to radiate heat, and if that doesn't occur adequately, they can warp (steel) or crack (cast iron). So you need good air movement to allow that radiation to happen. You are creating tremendous heat in an area of a few cubic feet, to then heat an area of hundreds or thousands of cubic feet. To get that vastly bigger area heated requires much air movement. The RMH, in addition to having a non-metal firebox and combustion chamber, spreads that heat into a many-cubic-foot bench or other mass which absorbs the heat and then releases it. What's shown here 'could' be problematic if run at too high a pace for too long. It's a good idea, as the mass absorbs heat and offers a barrier, but bricks or pebbles can't absorb heat as quickly as moving air. You might want more air space between the stove and the bricks, or maybe a fan forcing airflow to happen, if it was running hot enough to heat a good sized area for days at a time.

A dryer vent hose is one step above tinfoil, so it would shred fairly quickly. But, all you need to do is mount a solid baffle/deflector about a foot or two in front of the discharge and the chips will hit that and fall down into the trailer/wheelbarrow/tarp below. Picture the shape of a birdhouse, only larger, with no front or floor.

Going with your original question of using these boards as horizontal siding, there's a method* used with any siding boards you don't want to cup. Cedar is very stable wood, but still prone to splitting and cupping, (but not warping). The biggest concern with boards that thin and wide would be splitting. If you are in a damp climate, there's not a huge worry about drying the boards perfectly, depending on what you plan to do for a finish. You've likely seen cedar shingle or shake roofs or siding. Cedar absorbs and releases moisture very well if left as bare wood. That's how cedar shingles work- as it rains they absorb water and swell, staying tight and waterproof. If you plan to stain or seal your boards, you need to do both sides or they will cup from absorbing ambient moisture unevenly.
*Okay, back to siding. The method to prevent any siding boards from cupping is to saw a lengthwise kerf on the backside of the boards, 1/3 deep and every 4-6" of width. So for 1" lumber you'd set the blade depth of your circular saw at about 1/4 to 3/8" and run the length of the boards. For a 24" wide board you'd have about 5 cuts. This is a relief cut, and it works just like expansion joints used in concrete slabs. The board can 'move' and that kerf relieves the internal stresses, whether tension or compression, that would otherwise lead to splitting or cupping.
One last suggestion- I don't know how you have the lumber stored, but it should be stacked, stickered no more than 18" apart spacing with all stickers lining up vertically, heavy weight on top or strapped in a way that can be tightened every week or two as it dries and shrinks, and covered on top only. Definitely keep it out of the sun! Airflow is important to avoid mold growth.
As to fastening, that may be your biggest issue. Horizontal siding (I assume you mean to lap it) is only blind fastened on the top edge. Because these will be heavier than normal 6 or 8 inch siding boards, you may want to consider extra fasteners to keep that top edge from splitting out. Depending on what reveal you use, you might even do a staggered double row of nails.
Good luck, whatever you decide. Sounds like a neat project!

Dave Lotte wrote:  I know what you mean.  Dug up some of the loops for the heat pump last fall, and spent all winter thinking " if this thing freezes up on me.... what do i do "....

Just a thing I wonder about from time to time- What if you buried the loops below frost line, where the ground is always ~50 degrees, and just circulate that water, with no additional heat added. Would that not give you a mass/dwelling at 50 degrees? And now you only need to warm the house another 15-20 degrees which would take relatively little energy.
I know there has to be a flaw in my simple thinking or people would be doing it already!

This is awesome, and exciting to ponder, but unfortunately we are probably too far north (lat 60) for it to work all winter. Even with supplemental heat there's just not enough sun in dec/jan for anything to really grow. But, I think it's still worth doing to get a jump on spring and extend summer. (We would probably go with earth bags or berms to avoid the potential contamination from a petroleum based mass). Thanks for sharing the video!

Your logic is sound…other than the $1000 trailer being road worthy. The $1000 trailers usually need at a minimum tires and brakes.

Trailers are inspected regularly, just like the trucks that pull them. Without a current inspection (brakes, air lines, tires, lights, frame, springs, etc) you may find it difficult to get anyone other than a towing company to move one very far. The $1000 ones have generally been declared 'un-roadworthy' by the DOT, the owners, or both. That could be due to things like tires or brakes, but those are normal expenses for a trucking company, so usually there's also bigger issues like leaks or structural integrity.
As for insulation, using rigid board can lead to moisture issues from condensation between the metal and the sheets. Best way to go (not exactly cheap) is to spray foam the entire inside 2" thick (or more). 2" will give you about r-15. It would also be money well spent to have someone thoroughly inspect the roof for leaks or weak areas. Skylights done correctly could be a good option if you don't want windows, but you also need to consider some sort of venting for airflow. Skylights are not a great option on a flat roof unless you have a curb, which is a built up frame for the skylight to sit on. That will add to the height, which could be a consideration when moving it.

Thanks for sharing this! Love going down these rabbit holes of new ideas and possible discoveries. As he points out, the more we learn, the more we realize how much we don't know yet. I also love how scientific discovery accelerates. Looking at where we were even 50 years ago, it's stunning how far we've advanced with science and technology (not all good, admittedly).