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GSBN: Digest for 5/20/07



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-> Re: GSBN:Re Thermal Properties of Straw Bale Walls
     by "Andre_de_Bouter" forum@...
-> To Matts, Re Thermal Properties of Straw Bale Walls
     by "Jorgen_Munch-Andersen" jma@...
-> Re: GSBN:Re Thermal Properties of Straw Bale Walls
     by jswearingen@...
-> Re: GSBN:Re Thermal Properties of Straw Bale Walls
     by john@...


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

Date: 20 May 2007 04:26:33 -0500
From: "Andre_de_Bouter" forum@...
Subject: Re: GSBN:Re Thermal Properties of Straw Bale Walls

An other very effective way to create a snug fit arround the posts was
shown at the last ISBBC: Put a piece of lumber (that has the dimension
of your post) on the ground. 'Drop' your bale onto it .Cut of the excess
straw that sticks out on the side oposite of the piece of lumber. "Et
voila!"
This trick only works for bales layed flat and with posts that are
moderate to small in size. I forgot who showed us this 'gem' during the
conference.

Marty suggested that the 'French dipped' bales might give a good tight
fit between the bales. My experience is the opposite. If the bales are
dried after being dipped the diped sides get rock hard and do not
compress. If the bales are placed before they are dried there is more
chance for settling but this is a messier way of going about.

As for the test Nehemiah mentioned where the top was stuffed. A
suggestions (if such a test is ever to be repeated) is to compress and
stuff the wall from below with car jacks between the 'foundation' and
botom plate'.

Bye,

Andr#233# "drop that bale" de Bouter



John Swearingen a #233#crit :
>> 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@...
>>
>>
>> ----
>> For instructions on joining, leaving, or otherwise using the GSBN list,
>> send email to GSBN@...HELP in the SUBJECT line.
>> ----
>>
>
>
>
> --
> John Swearingen
> Skillful Means, Inc.
> Design and Construction
> www.skillful-means.com
>
>
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>
>
>


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

Date: 20 May 2007 05:17:52 -0500
From: "Jorgen_Munch-Andersen" jma@...
Subject: To Matts, Re Thermal Properties of Straw Bale Walls

Hi Matts,
 
Don't mind about the O, I don't know either how to type it if I don't have a
Danish keyboard.
 
The tests regarding heat insulation in our study were conducted at the Danish
Technological Institute, which has the apperatus and expertice to do the
meaurements, both standard measurements of the conductivity (lambda-value) and
guarded hot box tests. 
 
We used mainly small bale for the study but also som bigger, which had a
higher density. Therefore, the lambda-values were measured for different
densities. 
 
Afterwards, the person in charge at the Technological. Lars Olsen, did some
more tests on the influence of the density. I cannot find the right now, but
it was clear that the density did not influence the lambda-value very much. A
curve showing the lambda- -value vs. density will therefore not have a very
marked extreme. Thats what I mean by "flat" optimum. The best one for the
straw in question was, I think, about 80 kg/m3. 
 
The reason is the it is NOT the air that insulates. The insulation originates
from the resistance when the heat pass from one material to another. This
means that the ideal insulation material has very small cavities separated by
very thin walls. But the walls will also transmit heat, so when the wall
thickness is given there is an optimal size of the cavities. 
 
Since there are these two counteracting effects the actural density is not so
important. It also yields for mineral wool. But you will often see that for a
certain manufacturer the best insulating product is more dense than the normal
product, because smaller cavities requires more material to separate the
cavities.
 
As you might have guessed I do not belive that gabs in SB-walls should be
filled with straw-clay mix as the clay reduces the insulation ability. As long
as some straw are filled into all gabs it doesn't matter that much how dense
it is. Infiltration should be prevented by ensuring an air-tight layer on both
the inside and the outside.  
 
Sorry for the long explantion.
 
regards,
 
Jorgen   
 
 

________________________________

Fra: GSBN pa vegne af MattsMyhrman@...
Sendt: so 20-05-2007 02:11
Til: GSBN@...
Emne: 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







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Date: 20 May 2007 09:41:49 -0500
From: jswearingen@...
Subject: Re: GSBN:Re Thermal Properties of Straw Bale Walls

We have used a technique of buttering bales between courses...lay a soft
layer of mud on top of the last laid course of bales, then plop the next
bale on top.  The idea is to let the bales touch each other, but allow the
mud to squich into the voids created (mostly) by the tight strings.

We routinely fit out last course into the wall using car jacks and/or brute
force.  I trust this much more than stuffed straw for maintaining thermal
integrity, and reducing air infiltration and water penetration.

John "Mud Dauber" Swearingen

On 5/20/07, Andre de Bouter forum@... wrote:
>
> An other very effective way to create a snug fit arround the posts was
> shown at the last ISBBC: Put a piece of lumber (that has the dimension
> of your post) on the ground. 'Drop' your bale onto it .Cut of the excess
> straw that sticks out on the side oposite of the piece of lumber. "Et
> voila!"
> This trick only works for bales layed flat and with posts that are
> moderate to small in size. I forgot who showed us this 'gem' during the
> conference.
>
> Marty suggested that the 'French dipped' bales might give a good tight
> fit between the bales. My experience is the opposite. If the bales are
> dried after being dipped the diped sides get rock hard and do not
> compress. If the bales are placed before they are dried there is more
> chance for settling but this is a messier way of going about.
>
> As for the test Nehemiah mentioned where the top was stuffed. A
> suggestions (if such a test is ever to be repeated) is to compress and
> stuff the wall from below with car jacks between the 'foundation' and
> botom plate'.
>
> Bye,
>
> Andre "drop that bale" de Bouter
>
>
>
> John Swearingen a ecrit :
> >> 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@...
> >>
> >>
> >> ----
> >> For instructions on joining, leaving, or otherwise using the GSBN list,
> >> send email to GSBN@...HELP in the SUBJECT
> line.
> >> ----
> >>
> >
> >
> >
> > --
> > John Swearingen
> > Skillful Means, Inc.
> > Design and Construction
> > www.skillful-means.com
> >
> >
> > --- StripMime Report -- processed MIME parts ---
> > multipart/alternative
> >  text/plain (text body -- kept)
> >  text/html
> > ---
> > ----
> > For instructions on joining, leaving, or otherwise using the GSBN
> > list, send email to GSBN@...HELP in the
> > SUBJECT line.  ----
> >
> >
> >

>



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


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Date: 20 May 2007 11:26:19 -0500
From: john@...
Subject: Re: GSBN:Re Thermal Properties of Straw Bale Walls

G ' day

You can avoid all the chain sawing, squishing and car jacking and
stuffing by going load bearing.

T'is the way to go and with jumbo bales 2.4 x 900 x 600 laid one edge
the wall is super stong super fast to erect and 3 bales high gives you
2.7 + bottom and top plates - compression equals a wall height of
2.870.

Only problem is finding the right baler as they are as scarse as hens teeth.

Voila!

El Lupo.


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

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