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RE: GSBN:Re Thermal Properties of (french dipped) Straw Bale Walls



I am in agreement.  If you prepare the bales the day before (and leave them
covered with a plastic if the weather is really hot) they are still
workable, but less messy.  They do weigh a lot, so its harder work, but the
advantages are many and well worth the extra effort.

I suppose that since we are talking about clay, you could always let them
dry completely, and re-wet them before/after placing them in the walls to
make the clay soft again...although I have never done it this way.

Rikki Nitzkin
Aul?s, Lleida, Espa?a
rikkinitzkin@...
(0034)657 33 51 62 
www.casasdepaja.com (Red de Construcci?n con Balas de Paja)
 

> -----Mensaje original-----
> De: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] En nombre de Rene Dalmeijer
> Enviado el: jueves, 24 de mayo de 2007 10:04
> Para: GSBN
> Asunto: Re: GSBN:Re Thermal Properties of (french dipped) Straw Bale Walls
> 
> Chris,
> 
> I fully support you in this it is essential that the dipped bales are
> used quite rapidly after dipping. This is a messy business but working
> with two people to lift and place the bales makes a big difference. The
> bales tend to fit in much better the need for stuffing joints is almost
> diminished to zero.
> 
> Another tip once the bales are in place a tamping of the still tacky
> bale surfaces with a plank and a hammer will align and flatten the bale
> surface to a great extent. The best technique is to lay the plank
> across the bale joints and then tamp. To work effectively the clay rich
> slip should still be quite moist.
> 
> Rene
> On May 24, 2007, at 03:50, cmagwood@...:
> 
> > I'd like to kick in on the "French dipped" method, as I
> > believe they do a great job of helping to provide a really
> > good "seal" across the entire face of the wall. It would
> > make sense that if dipped bales are left to dry before
> > being stacked that they wouldn't work as well, but they
> > shouldn't go in when dried, but when slightly tacky. Then
> > the straw/clay that goes in the gaps bonds very well to
> > the bales and makes, for me, the best wall surface going.
> >
> > Chris
> >
> >>
> >> 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&eacute; "drop that bale" de Bouter
> >>
> >>
> >>
> >> John Swearingen a ?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@...
> >>>>
> >>>>
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> >>>
> >>>
> >>> --
> >>> John Swearingen
> >>> Skillful Means, Inc.
> >>> Design and Construction
> >>> www.skillful-means.com
> >>>
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