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insulated rammed earth

 
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This an introduction to insulated rammed earth. SIREWALL is the acronym for this modernized green building technique and it stands for: Structural Insulated Rammed Earth. In this video, we’re meeting Tony Johnson from Earth House Holdings to learn about rammed earth construction, and to get a peek at the rammed earth home he is building for his family in British Columbia, Canada.

The rammed earth mixture in this project contains soil aggregates (~90%), cement (~9%), and pigment (less than 1%). It is mixed and deposited into plywood forms, then it is rammed with a pneumatic tamper to squish the earth down, and finally, it is cleaned up with a manual tamper. The wall is built in lifts of 6 inches at a time which gives the wall the striations and lines that are typical of rammed earth.

Some of the benefits of rammed earth as a green building technique include the fact that it is energy efficient due to the thermal mass and thermal break created by the insulation. It is also an airtight material which means that there’s little heat loss from a poor air barrier. Some studies have also shown that it is fire resistant as well.

youtube video
 
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I have felt that insulated rammed earth represents a culmination of some ideas about annualized thermal inertia for some time now. It seems most reasonable to me to have your structural material also be an earth-connected thermal battery.

My most recent non-wofati-based approach for using this idea actually came out of the astronomical prices builders are seeing for lumber these days, prices that don't seem to be diminishing any, even though the commodity price has dropped significantly.

I was actually thinking about using insulated steel quonset huts, perhaps arranged in a cross formation oriented to the solar cardinal points, on a slab of rammed earth insulated either sub-grade, or with a buried perimeter skirt of insulation, a metre out around the perimeter. I would then create interior walls of rammed earth suitable for the support of an internal second story, with the quonset hut structure forming a structurally independent insulated shell.

Whatever the specifics, this approach would necessitate a larger-sized quonset hut be used, with a peak two, or even three, storeys high. This would offer internal dimensions that would allow for the thickness of wall required without resulting in a space that feels unduly crowded.

Incidentally, I was thinking about using a battery-powered electric vibratory rammer with a shoe size of 11"x13". This would easily fit in a form 12" wide.

But just to address the original thrust of the thread, I think a masonry thermal battery that is also the structure, and is insulated, possibly coupled with a ground-based heating and cooling system, is a terrific way to be thinking about energy-efficient living, whatever auxilliary methods of heating or cooling are employed.

-CK
 
John C Daley
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Chris, I am a bit confused by your notes.
Rammed earth is athermal battery.
Interior walls of a quornset may need to be partially compressed bricks up against the steel ceiling.

vibratory rammer with a shoe size of 11"x13"


I think you will not get the best compaction with a rammer that size.
 
Chris Kott
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Hey John,

Sorry about the confusion. I am simply talking about using rammed earth as a slab base for a quonset hut-based building. Inside that building, tied into the slab, probably with rebar or pins, would be a self-supporting internal structure with a bedroom on top. As the quonset hut structure is self-supporting on the slab, the internal structure would need only support itself.

I know that rammed earth, and compressed earth block, and all externally-insulated masonry, really all masonry, will act as a thermal battery. I was just saying that I like the idea, that it works well to my way of thinking with other ideas involving ATI, regardless of whether it's being heated by a candle, solar gain, an RMH, woodstove, or something more conventional.

I like CEB. They also make sense to me, but setting up the process where it doesn't already exist looks pretty cost-prohibitive to me unless I make a go at an in situ CEB production business, using a more automated process, like what's done with those asphalt road-building assemblies.

Rammed earth, however, is much more accessible to me. There is still cost involved, but both require earth-moving equipment at similar scales, and I can pick up used concrete forms on kijiji or craigslist.

If I remember, you're the expert on this stuff. I would love your advice. If I was building rammed earth internal walls in the manner described, what do you feel the thinnest wall thickness could be, using a vibratory rammer or tamper?

-CK
 
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Great thread, and I am late to the party, but am also looking to use CEB in a stem wall application, and below grade.   Hopefully, this doesn't hijack it too far off track.

I, too, am finding there is a transition from "really cheap and a few blocks an hour" to $65K +S/H to produce all the needed block in about one good day of running...and moreover, for aesthetics as much as anything, I am looking for 18" thick, which is its own challenge.

I saw the comment on the plate compactor, which was the search that led me here.  In my case, I am entertaining the thought of using a 2nd hand hydraulic compactor head like you would put on an excavator (example - https://www.impulse-evo.com/product/vibrating-compactor-impulse-v30/).   40 Hz, with a few T each impact should go a long way, and a simple weld onto the foot of the appropriate size, and let the whole thing slide on rails up and down (so no excavator).    And use this as mold mold press, with additional weigh if needed.  Then, as much width as I can get on 18" length, sacrificing time for width, if that makes sense.  

This is from read an interesting journal article where the compaction was tied to some net total impact energy (https://www.researchgate.net/publication/223019143_Performance_of_compacted_cement-stabilised_soil), and this apparently works better than the squish, the slow squish, and even the squish with a hold.

Unfortunately, I don't have one of these heads, so am looking for some degree of confidence before going to find one and build a test frame.  I have to assume there is a minimum level of intensity needed, that is quite dependent on water content, and so a lot of testing....but hat assumes it has a hope of working in the first place.  Hoping to find someone who has tried something like this for some pointers, or else point out the obvious flaw that i am missing?


 
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