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Laying bales end-in/out?

 
Kevin EarthSoul
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I live in Nebraska, which faces the challenge of having both very cold winters and very hot summers. Our total of heating degree days plus cooling degree days is higher than just about anywhere.

I would like to superinsulate with R Values >50, with as much earth-moderation and passive solar gain as possible. With this in mind, I am interested in building in a hybrid style of earthbag (possibly scoria-filled) below grade and strawbale above grade, with maximum passive-solar design.

Earthbags are highly conducive to round-house design, while strawbales are not. But it occurs to me that standard 2-string strawbales (36"x18"x14") could be trimmed in such a way that they could be shaped into trapezoids, without cutting through the twine, if they were trimmed on the 36"x14" plane. This would leave a long end of 18" and a short end of a certain length that depends on the radius of the wall. They could then be tightly laid flat in an end-in orientation. This would make a 36" thick wall before plastering. South-facing windows would have to be deeper, but could possibly be larger, because the thick walls would allow for a narrower pillar between windows.

I'm not sure how well this would work, and was wondering if anyone else has attempted this orientation of strawbale building. Is there less R- per inch due to the orientation of the straw? Does it increase moisture transport?
 
Robert Ray
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Trimming bales is common to create a curve. You wouldn't notice any difference in R-value per inch other than the increase in width due to your proposed orientation. There would be no transpiration issues once the plaster/stucco layer is applied.
 
Tim Evers
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Did you build? I live in Nebraska and would like to pitch in effort for the hands on experience. I've been doing some plaster tests on a 6' x 6' wall in my yard and we appear to have excellent clay around Kearney. Hope Summer is treating you well.
 
Kevin EarthSoul
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I have not built. I have no land, as of yet. I'm thinking ahead about the vast differences in temperature we experience here in Nebraska between Summer and Winter, and thinking that super-insulation is more important than thermal mass, although both can be used. If strawbales have an R-value of 2.5/inch (if dried properly), that would mean an R-Value of 90. Even if they only achieve R-2/inch, that is 72, which is more than enough for Nebraska.

Another concern I have, however, is condensation. If the straw is oriented this way, it would wick moisture more rapidly through the walls, and once it reaches a freezing temperature somewhere in the wall during the Winter, it'll freeze, which can't be good.

 
Robert Ray
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I don't think that you would ever see enough condensation built up in a straw bale wall to create a condition in wich it would freeze. A properly constructed foundation and protection from moisture from above either with extended eaves or water collection would prevent the bales from getting damp.
The first straw bale home I had ever seen was in Nebraska.

http://thesustainablehome.net/?p=173
 
Kevin EarthSoul
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Robert Ray wrote: I don't think that you would ever see enough condensation built up in a straw bale wall to create a condition in wich it would freeze. A properly constructed foundation and protection from moisture from above either with extended eaves or water collection would prevent the bales from getting damp.
The first straw bale home I had ever seen was in Nebraska.


The concern would be for moisture from breathing, cooking, and showering inhabitants. I know that strawbale is vernacular to Nebraska, but it's not usually oriented end-in/out for such a thick wall.
 
Robert Ray
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Straw bale walls are constantly breathing and the type of transpiration that would allow that much condensate to get into the walls would probably not occur since the walls do breathe. Greenhouses built with straw bales and properly stuccoed are far more humid than a home would be and there seems to be no issue that results from that humidity.
 
R Scott
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They will not breathe as well both due to the thickness and the direction of the fibers. Properly plastered and they should still be OK if you don't build a steam room or sauna.

My bigger concern is how stable they will stack. I think you would be better off stacking two walls. You can stack them grain up (18" tall by 36" wide brick face), you can bend them to a curve fairly easily. If you stack two walls with offset seams (both horizontal and vertical) and tie them together--it will be a remarkably strong wall.
 
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