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GSBN: Digest for 10/16/02



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-> Re: GSBN:Re: STC of Straw bales
     by "Coralie & Andre de Bouter" m.ep@...
-> Re: GSBN:STC for bale walls
     by larskeller@...
-> GSBN: Re: STC of Straw bales
     by Derek Roff derek@...
-> Re: GSBN:Re: STC of Straw bales
     by Rene Dalmeijer rened@...


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

Date: 16 Oct 2002 04:40:14 -0500
From: "Coralie & Andre de Bouter" m.ep@...
Subject: Re: GSBN:Re: STC of Straw bales

Hi,

In France there is a vicous rumour going arround that SB walls are a poor
sound insulator. Arnaud Cauwel wrote a report for his school of architecture
in which he claimed that straw (because of its low mass) insulates poorly.
No numbers or test data is given.

Lars informed me on the Danish sound test some while ago, and specifficly
stated that I cannot quote him since the info is not official yet.
However I think it is safe to say that the result of the test was probably
greatly influenced by the post and beam structure and that the results were
not very impressive (for as far as I can understand them :-) 'cause the
universe of sound is complex thing. I feel that a beam (to carry the floor
for instance) that goes through the inside plaster and sits on the ring beam
would probably give a great transmission of sound to the outside plaster
just next to the ring beam, circumventing the 90% of the SB wall.

And than there is the question of indoor accoustics. Friends of us want to
build a SB Art & concert hall, so they are also concerned about how the
sound will be for the audience and what we can do to enhance that quality
with the shape and surface of the walls.  Any hints?

Bye
Andre
www.la-maison-en-paille.com


- ----- Original Message -----
From: Rene Dalmeijer rened@...
To: GSBN GSBN@...
Cc: J.J.de.Groot@...; Rob Kaptein ramstrobouw@...
Sent: Tuesday, October 15, 2002 11:01 PM
Subject: Re: GSBN:Re: STC of Straw bales


> Bruce, Tom
>
> There is a chance that we will be doing a test here regarding the SB
> acoustic insulation value. The test if executed will be in a test
facillity
> at the Eindhoven University normally used to test window frames so I
expect
> that the measured values will till how well the test facilty functions. I
> am sure that a properly executed SB wall has excellent sound insulation
> properties far exceeding normal brick walls. What are STC numbers? We
don't
> use this qualification here. BTW the test will incorporate a spectral
> distribution.
>
> At 12:22 AM 10/15/02, you wrote:
> > > I recall there was some discussion of SB sound transmission on the
> > > list some time ago, including anecdotal evidence provided by the
> > > Straw Wolf's rock band or some such.  Anyone have any solid numbers
> > > for Katie?  Failing that, anyone have any good stories to tell? ;-)
> >
> >
> >To my knowledge, no formal tests have been done to provide STC numbers at
> >various sound frequency levels (such as building engineers sometimes
need).
> >We all know they're mighty quiet, and that it's hard to shout through a
wall
> >to someone on the other side, but don't have the exact geek numbers as
yet.
> >
> >Or, if someone does, I would very much appreciate learning of it, as the
> >culmination of the EBNet test program aims to be a compilation of ALL
> >testing of ALL sorts done to date - by EBNet or by others.
>
> Greetings,
>
> Rene Dalmeijer
>

>




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

Date: 16 Oct 2002 06:15:19 -0500
From: larskeller@...
Subject: Re: GSBN:STC for bale walls

Dear GSBNers.

As Matts writes below we have done one test in Denmark. A "field" test on an
existing house. Only one test. No lab-tests.
As the results are not yet public and I want to stay on good terms with the
Danish National Building Test Institute you will have to excuse me for not
saying more right now.

I will though ask mr Official man whether I may let it slip out into the open.

As Andre points out the results are not fantastic, eg just not good enough for
a dividing wall between two semidetached houses, unless a thicker plaster
layer is applied.

Yours sincerely

Lars keller


MattsMyhrman@...:
> Dear Katie and GSBNers,
> 
> Last year I helped Lars Keller clean up an English-language
> version of a 
> summary of some testing to determine the "airsound
> insulation" of straw-bale 
> walls.  They concluded that the walls tested had an airsound
> insulation 
> value,"R'' w" (the w is actually a subscript), of about 54
> dB.  Lars should 
> be able to tell us all how to access this summary.
> 
> Hope this helps.
> 
> Matts Myhrman / Judy Knox                       
> mattsmyhrman@...     
> Out On  Bale, (un) Ltd.                                  
> 2509 N. Campbell Ave., #292                      
> judyknox42@...
> Tucson, AZ  85719                                       
> Office message phone  (520) 622-6896
> 


~~~

Lars Keller
Friland 12 B
Feldballe
8410 Ronde
Danmark

0045-20240505
larskeller@...
~~~


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

Date: 16 Oct 2002 16:17:16 -0500
From: Derek Roff derek@...
Subject: GSBN: Re: STC of Straw bales

- --On Wednesday, October 16, 2002 10:47 AM +0200 Coralie & Andre de 
Bouter m.ep@... wrote:

> In France there is a vicous rumour going arround that SB walls are
> a poor sound insulator. Arnaud Cauwel wrote a report for his school
> of architecture in which he claimed that straw (because of its low
> mass) insulates poorly. No numbers or test data is given.

This is like saying birds can't fly because they don't have feathers: 
wrong data, wrong theory.  While straw bales are not terribly dense, 
they do contain substantial mass.  A plastered strawbale wall will 
have about half the weight/mass of an adobe or stone wall in an 
equivalent structure (per square foot/meter of wall surface, or per 
lineal foot/meter of a wall of the same height).  A plastered 
strawbale wall will weigh more than twice what a brick wall weighs. 
There is a great deal of mass there.

In attenuating sound, mass is important.  However, thickness also 
matters.  The same amount of mass will cut the sound more if it is 
deployed at lower density, in greater thickness.  Rigid, elastic 
materials (like steel) will transmit sound more effectively than 
softer materials with multiple internal planes of reflection, like 
foams.  Strawbale walls score well on all three counts:  high mass, 
great thickness, and soft, amorphous material.

Hard plasters do lead to echoes, so the inside of a SB house may not 
be the perfect environment for a musical recital.  The non-strawbale 
parts of a structure, such as roof, windows and floor, can have a 
significant influence on sound performance.  But if other things are 
equal, a SB house will have sound insulation properties superior to 
most common building materials, and on par with the best.

Still, our French SB friends have a problem.  It's often hard to 
fight stupidity and prejudice with numbers or logic.  The people who 
are willing to spend a few minutes in a SB house will be convinced.

Derek Roff
Language Learning Center, Ortega Hall Rm 129, University of New Mexico
Albuquerque, NM 87131  505/277-7368 fax 505/277-3885
Internet: derek@...


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

Date: 16 Oct 2002 16:37:34 -0500
From: Rene Dalmeijer rened@...
Subject: Re: GSBN:Re: STC of Straw bales

Andre,

I suppose you also read John Glassfords mail with ale in hand and decibel 
meter in other. Although his measuremnts seem crude he did very well by 
taking note of ambient sound levels. I expect a reasonably executed SB wall 
without acoustic defects like the ones described by Andre will perform in 
the region of 60dB and upwards.

The fact that SB walls are a poor sound insulator is a vicious rumor. I 
presume that Arnoud Cauwel is a promoter of pisee and other earth 
techniques. Heavy mass like a meter of concrete are necessary for very low 
frequencies ie <60 Hz above this most simple building structures, even 
quite light ones, can dampen sound quite effectively if executed properly. 
It is even possible to reach -60dB damping with a few not too thick panes 
of glass (like in sound studios).

Besides mass stiffness and de-coupling are very important for acoustic 
sound insulation. The relatively low stiffness of a SB wall with earthen 
plaster are ideal. The fact that the cavity between the two outer stucco 
shells is filled with straw is excellent acoustic damping. Beware to be 
careful and fill all cavities and voids with straw clay, avoid any direct 
mechanical contacts between inner and outer shells, these will seriously 
degrade sound damping performance. Contrary to what you would expect 
loosely packed bales will perform better then very tightly packed (rice is 
ideal). Pay a lot of attention to all openings and edges these are the weak 
points. An air leak of only a 1mm^2 will seriously degrade performance. 
Door openings and windows are literally acoustic holes in the wall these 
need special detailing and attention to even remotely approach the 
performance of the walls. Doors even double ones have a poor performance. 
The gaskets and seals in the doors should be double or even triple but even 
then there is the problem that over time the seals will degrade and leaks 
will occur. The type of doors you are aiming for is more like a steel 
watertight door in a ship then a house door with multiple closing bolts and 
tightening clamps.

In conclusion I would like to add due to the nature of a SB wall (homogenic 
continuous surface) the wall is not the problem but the connections between 
the wall and all other structures incorporated or surrounding it. I 
strongly suspect that most sound insulation tests executed on SB walls are 
measuring the defects of other structural components or mistakes in the 
test procedure (a non calibrated sound source, Background noise etc.)

Andre regarding room acoustics. Here are some simple rules of thumb 
depending on the type of acoustics you want ie very lively to very well 
damped. Soft acoustic instruments require a live room. Loud amplified sound 
a dead room. The single most important parameter is the reverberation time 
and level. The harder the surfaces the livelier the sound. A bathroom is 
lively hence your drive to sing even if you can't. The opposite is standing 
on top of snow bound hillock. The bigger and harder the room the longer the 
reverberation time ie a cathedral. Next the relative dimensions. An oblong 
box (like Concertgebouw Amsterdam) approaches the ideal. Preferably the 
dimensions relate to each other approximately in the following manner 2-3-5 
(I don't have the exact figures at hand at the moment but this ratio will 
avoid predominant harmonic resonances and standing waves) the exact ratios 
depend on the size and acoustic reflectiveness. I personally prefer rooms 
without parallel surfaces thus avoiding standing waves. I think if you 
build a room with clay stucco and wooden flooring and a well pitched 
ceiling you will have quite acceptable acoustics for acoustic performances. 
If its too live you can always add some damping afterwards


At 10:47 AM 10/16/02, you wrote:
>Hi,
>
>In France there is a vicous rumour going arround that SB walls are a poor
>sound insulator. Arnaud Cauwel wrote a report for his school of architecture
>in which he claimed that straw (because of its low mass) insulates poorly.
>No numbers or test data is given.
>
>Lars informed me on the Danish sound test some while ago, and specifficly
>stated that I cannot quote him since the info is not official yet.
>However I think it is safe to say that the result of the test was probably
>greatly influenced by the post and beam structure and that the results were
>not very impressive (for as far as I can understand them :-) 'cause the
>universe of sound is complex thing. I feel that a beam (to carry the floor
>for instance) that goes through the inside plaster and sits on the ring beam
>would probably give a great transmission of sound to the outside plaster
>just next to the ring beam, circumventing the 90% of the SB wall.
>
>And than there is the question of indoor accoustics. Friends of us want to
>build a SB Art & concert hall, so they are also concerned about how the
>sound will be for the audience and what we can do to enhance that quality
>with the shape and surface of the walls.  Any hints?
>
>Bye
>Andre
>www.la-maison-en-paille.com
>
>
>----- Original Message -----
>From: Rene Dalmeijer rened@...
>To: GSBN GSBN@...
>Cc: J.J.de.Groot@...; Rob Kaptein ramstrobouw@...
>Sent: Tuesday, October 15, 2002 11:01 PM
>Subject: Re: GSBN:Re: STC of Straw bales
>
>
> > Bruce, Tom
> >
> > There is a chance that we will be doing a test here regarding the SB
> > acoustic insulation value. The test if executed will be in a test
>facillity
> > at the Eindhoven University normally used to test window frames so I
>expect
> > that the measured values will till how well the test facilty functions. I
> > am sure that a properly executed SB wall has excellent sound insulation
> > properties far exceeding normal brick walls. What are STC numbers? We
>don't
> > use this qualification here. BTW the test will incorporate a spectral
> > distribution.
> >
> > At 12:22 AM 10/15/02, you wrote:
> > > > I recall there was some discussion of SB sound transmission on the
> > > > list some time ago, including anecdotal evidence provided by the
> > > > Straw Wolf's rock band or some such.  Anyone have any solid numbers
> > > > for Katie?  Failing that, anyone have any good stories to tell? ;-)
> > >
> > >
> > >To my knowledge, no formal tests have been done to provide STC numbers at
> > >various sound frequency levels (such as building engineers sometimes
>need).
> > >We all know they're mighty quiet, and that it's hard to shout through a
>wall
> > >to someone on the other side, but don't have the exact geek numbers as
>yet.
> > >
> > >Or, if someone does, I would very much appreciate learning of it, as the
> > >culmination of the EBNet test program aims to be a compilation of ALL
> > >testing of ALL sorts done to date - by EBNet or by others.
> >
> > Greetings,
> >
> > Rene Dalmeijer
> >
> > ----
> > For instructions on joining, leaving, or otherwise using the GSBN list,
>send email to GSBN@...HELP in the SUBJECT line.
> > ----
> >
>
>


Greetings,

Rene Dalmeijer



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

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