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GSBN: Digest for 5/19/07



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-> Re: GSBN:Re Thermal Properties of Straw Bale Walls
     by john@...
-> Re: GSBN:Clay/ Earth: Multilingual Terminology Glossary
     by "Andre_de_Bouter" forum@...
-> Re: GSBN:Re Thermal Properties of Straw Bale Walls
     by Martin Hammer mfhammer@...
-> Re: GSBN:Re Thermal Properties of Straw Bale Walls
     by jswearingen@...
-> Re: SV: GSBN:Re Thermal Properties of Straw Bale Walls
     by MattsMyhrman@...


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Date: 18 May 2007 23:52:08 -0500
From: john@...
Subject: Re: GSBN:Re Thermal Properties of Straw Bale Walls

G ' day Nehemiah

Andrew Webb replied on GSBN but here is a copy:

For what it's worth, BERS Pro, the energy-rating software, gives a value
of R5.25 for a 520 thick rendered bale wall and R9.80 for a 970 thick
wall (allowed 35mm render both sides).

- -AW

> Also, your Q about how compaction affects R-value is a potent question.  If
> hot box testing wasn't so expensive and time consuming, or if there were

I am 100% sure and convinced that the jumbo bales are far better
compacted than the small standard bales.  The balers that make jumbo
bales are far more sophisticated than the standard small balers.  I
cannot prove it but the look and feel of a jumbo bale especially when
cut with a chain saw proves it to me personally.

The problem with jumbo bales is that they are heavy and need machinery
to move them and also they take up a larger footprint.  However they
are easier to build with provide very straight walls and can go very
high load bearing, at least to 5.6 metres and probably higher.  As for
time they are much quicker to build with.

Hence my preference in using them and even on edge they give very strong
walls.

Thanks again to all of you for the answers and for the questions that
need answering.

John Glassford.
<a  target="_blank" href="http://www.coolamonrotary.com/kili";>http://www.coolamonrotary.com/kili</a>


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Date: 19 May 2007 04:05:51 -0500
From: "Andre_de_Bouter" forum@...
Subject: Re: GSBN:Clay/ Earth: Multilingual Terminology Glossary

Thanks Dirk!

By the way Matts, the next (book) project of this Gaulois is translating
and publishing Bruce's "Design of SB buildings". (after the pictures and
the inspiration follow the numbers and hard facts)

Best regards to all of you,

Andr#233#




Dirk Scharmer- FASBA a #233#crit :
> Maybe this is interesting for someone:
>
> A Multilingual Terminology Glossary for Clay/ Earth construction for
> translation from/ into english, french, spain, russian, german on
> <a  target="_blank" href="http://www.dachverband-lehm.de/de/05_wissen/05-4_wissen_glossar.htm#";>http://www.dachverband-lehm.de/de/05_wissen/05-4_wissen_glossar.htm#</a>
>
> Dirk Scharmer
>
> -----------------------------------------------
> Fachverband Strohballenbau Deutschland e.V.
> Auf der Ruebekuhle 10
> D- 21335 Lueneburg
> Tel. 00 49 4131- 2278649
> Fax. 00 49 4131- 2278648
> Internet: www.fasba.de
> Email: ds@...
>
> ----
> For instructions on joining, leaving, or otherwise using the GSBN list, send
email to GSBN@...HELP in the SUBJECT line.
> ----
>
>
>
>


----------------------------------------------------------------------

Date: 19 May 2007 11:55:11 -0500
From: Martin Hammer mfhammer@...
Subject: Re: GSBN:Re Thermal Properties of Straw Bale Walls

Nehemiah -

Good explanations.

You talked about the straw-stuffed gaps at the top and sides of a wall as
being places where convective losses could occur.  So I'll add the thermal
importance of stuffing vertical joints/gaps between bales for the same
reason of limiting convective losses.  (This would also be important between
bales and "posts" that go mostly or all the way through the thickness of the
wall.  I've seen I-joists or steel trusses used this way.)

Straw-clay seems the best material for this purpose, although too much clay
might increase conductive heat loss in the stuffed area.  Horizontal joints
between bales don't seem to be an issue because the weight of the bales
appear to cause the surfaces to lock in well enough to limit air movement
between them (although the French dipped bales might seal that joint even
better, and bales on-edge probably nestle together better than laid-flat).

Then there's always the question of what material is between the bottom of
the plates, and what the insulative qualities of the roof bearing assembly
are.  And then there's the ceiling/roof, and the windows/doors, and the
amount of infiltration throughout, and . . . . .

Martin Hammer


> John,
>
> I did not see a response from Andrew.  Was that off list?  I am always
> interested in what new or other information people have on the thermal
> properties of straw bale construction.  Care to share his input?
> Also, your Q about how compaction affects R-value is a potent question.  If
> hot box testing wasn't so expensive and time consuming, or if there were
> funders lined up to pay for it, I'd already have an answer for you.  There
> are a number of confounding factors, so until someone has done the actual
> research, we can throw around lots of theories.
> For example, it is air that creates the insulation value of almost
> everything used for wall insulation.  ,,,not the spun glass, not the solid
> portions of the foam, not the cellulose, not the straw.   Therefore, if
> bales are compacted too much, one would expect the insulation value to go
> down.  But, what is "too much?"  If bales are too loose, then the air can
> circulate in the air pockets and research HAS shown that this can lead to
> convective currents that lead in turn, to a dramatic drop in R-value.  That
> was one of the causes (we think) for the relatively low R-values in the ATI
> lab tests in Fresno, CA.  Once we stacked the bales in the hot box wall
> opening, and compressed them as they'd be in a building wall, we had a six
> inch gap at the top.  We filled it with straw as tightly as we could, but
> we are not match for either a baler or truckers' strap tightening levers,
> so we KNOW that the top (where the greatest amount of heat exchange would
> naturally occur anyway) was much looser than the rest of the wall.  Ditto
> the sides, though those gaps were significantly smaller (so perhaps, harder
> to compact straw into).
> Further, though in theory greater compaction - after the optimal point -
> will lead to a decreasing R-value, no tests have yet shown that to be the
> case.  Perhaps we just haven't found the optimal compression force yet.
> Perhaps the theory is wrong.
> Lastly, I would question your assertion that jumbo bales are "naturally
> compacted a lot more than the smaller bales."  It is mechanically more
> difficult to compact a larger bale to the same density as a smaller one.  I
> am not saying that the machinery isn't designed to do so - perhaps it is.
> But, from a pure physics point of view, it is not "natural" as you said.
> One way to verify whether the compaction is greater or not is to measure
> the water content and density.  Rice straw bales in California (the ones we
> tested) are typically at least 8 pounds per cubic foot at a moisture
> content of about 6%.  Do you have similar data on the Aussie jumbo bales?
> If you want to get an accurate reading of the moisture content (more
> accurate than a moisture meter stuck a random depth into the bales), let me
> know and I will send you (offline) a description of how we did it.  The
> density (#/cf or kG/cM) is pretty easy, assuming you can weigh a
> representative sample of the bales.
> Hope this helps.
> Thanks,
>
> Nehemiah Stone
> stoneandstraw@...




----------------------------------------------------------------------

Date: 19 May 2007 14:48:53 -0500
From: jswearingen@...
Subject: Re: GSBN:Re Thermal Properties of Straw Bale Walls

>Straw-clay seems the best material for this purpose, although too much clay
might increase conductive heat loss in the stuffed area. <

...for several other reasons, too.  When straw is stuffed in joints it's
relatively loose and so provides a ready channel for moisture into the
depths of the wall.  Straw-clay will form a seal against moisture entering
the joints between the bales.  In addition, it stops air infiltration and
can be screeded off to make a flat plain for plaster, thereby reducing the
occurance of cracks that result from abrupt changes in the thickess of the
plaster.  Also, it's fun to get dirty....

"Hurlen" John Swearingen

On 5/19/07, Martin Hammer mfhammer@... wrote:
>
> Nehemiah -
>
> Good explanations.
>
> You talked about the straw-stuffed gaps at the top and sides of a wall as
> being places where convective losses could occur.  So I'll add the thermal
> importance of stuffing vertical joints/gaps between bales for the same
> reason of limiting convective losses.  (This would also be important
> between
> bales and "posts" that go mostly or all the way through the thickness of
> the
> wall.  I've seen I-joists or steel trusses used this way.)
>
> Straw-clay seems the best material for this purpose, although too much
> clay
> might increase conductive heat loss in the stuffed area.  Horizontal
> joints
> between bales don't seem to be an issue because the weight of the bales
> appear to cause the surfaces to lock in well enough to limit air movement
> between them (although the French dipped bales might seal that joint even
> better, and bales on-edge probably nestle together better than laid-flat).
>
> Then there's always the question of what material is between the bottom of
> the plates, and what the insulative qualities of the roof bearing assembly
> are.  And then there's the ceiling/roof, and the windows/doors, and the
> amount of infiltration throughout, and . . . . .
>
> Martin Hammer
>
>
> > John,
> >
> > I did not see a response from Andrew.  Was that off list?  I am always
> > interested in what new or other information people have on the thermal
> > properties of straw bale construction.  Care to share his input?
> > Also, your Q about how compaction affects R-value is a potent
> question.  If
> > hot box testing wasn't so expensive and time consuming, or if there were
> > funders lined up to pay for it, I'd already have an answer for
> you.  There
> > are a number of confounding factors, so until someone has done the
> actual
> > research, we can throw around lots of theories.
> > For example, it is air that creates the insulation value of almost
> > everything used for wall insulation.  ,,,not the spun glass, not the
> solid
> > portions of the foam, not the cellulose, not the straw.   Therefore, if
> > bales are compacted too much, one would expect the insulation value to
> go
> > down.  But, what is "too much?"  If bales are too loose, then the air
> can
> > circulate in the air pockets and research HAS shown that this can lead
> to
> > convective currents that lead in turn, to a dramatic drop in
> R-value.  That
> > was one of the causes (we think) for the relatively low R-values in the
> ATI
> > lab tests in Fresno, CA.  Once we stacked the bales in the hot box wall
> > opening, and compressed them as they'd be in a building wall, we had a
> six
> > inch gap at the top.  We filled it with straw as tightly as we could,
> but
> > we are not match for either a baler or truckers' strap tightening
> levers,
> > so we KNOW that the top (where the greatest amount of heat exchange
> would
> > naturally occur anyway) was much looser than the rest of the
> wall.  Ditto
> > the sides, though those gaps were significantly smaller (so perhaps,
> harder
> > to compact straw into).
> > Further, though in theory greater compaction - after the optimal point -
> > will lead to a decreasing R-value, no tests have yet shown that to be
> the
> > case.  Perhaps we just haven't found the optimal compression force yet.
> > Perhaps the theory is wrong.
> > Lastly, I would question your assertion that jumbo bales are "naturally
> > compacted a lot more than the smaller bales."  It is mechanically more
> > difficult to compact a larger bale to the same density as a smaller
> one.  I
> > am not saying that the machinery isn't designed to do so - perhaps it
> is.
> > But, from a pure physics point of view, it is not "natural" as you said.
> > One way to verify whether the compaction is greater or not is to measure
> > the water content and density.  Rice straw bales in California (the ones
> we
> > tested) are typically at least 8 pounds per cubic foot at a moisture
> > content of about 6%.  Do you have similar data on the Aussie jumbo
> bales?
> > If you want to get an accurate reading of the moisture content (more
> > accurate than a moisture meter stuck a random depth into the bales), let
> me
> > know and I will send you (offline) a description of how we did it.  The
> > density (#/cf or kG/cM) is pretty easy, assuming you can weigh a
> > representative sample of the bales.
> > Hope this helps.
> > Thanks,
> >
> > Nehemiah Stone
> > stoneandstraw@...
>
>

>



- --
John Swearingen
Skillful Means, Inc.
Design and Construction
www.skillful-means.com


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Date: 19 May 2007 18:24:56 -0500
From: MattsMyhrman@...
Subject: Re: SV: GSBN:Re Thermal Properties of Straw Bale Walls

Jorgen,

Forgive this computer Luddite the lack of the "/" through the "o" in your
name.   I keep promising myself that I'll learn how to do that stuff but life
keep intervening.   That said, I'd appreciate some clarification of what you
mean
by "The optimum [density} is very flat for most materials, and it surely is
flat for straw."

Matts (he of the maximum cranial density) Myhrman



**************************************
 See what's free at .


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