[Strawbale] SB R-values
asbn at baubiologie...
Thu Mar 19 00:00:44 CET 2009
Hot theme, I think...
Sorry, I mixed up lambda with R-value.
Dirk, what I meant with saying that I can't hear the argument with the more
realistic lambda-value anymore is: lambda-value is not just a description of
the thermal performance of a building- oder insulation material, it is also
pure money for builders, at least in Austria and G..., well some other
countries. The better the U-value (which depends on lambda-value), the more
the money you get from the state, the more strawbalehouses are build (and
sold), the faster strawbale-construction is accepted as a serious solution
Let me remind you, that building-laws and values are usually not a result of
trying to find the truth but a more or less ruthless "fight" of industrial
lobbies for their own products. With all tricks. To be realistic in that
case means giving up the competition before it really began. Just an
example: Schaumglasschotter (expanded glass) developed as THE sustainable
"eco"-material for foundations (instead of XPS) with a good lambda-value. It
was recommended by serious studies, books and publications. What happened?
Schaumglasschotter was classified as moisture-sensitive and the lambda-value
got a 20% addition. Therefore now you need more of the material (to reach
the same thermal performance as before) which means a higher price so that
many people decide to use XPS again. But enough of that.
Peter, what we tried to understand is the reason for the different
lambda-values in different tests in different countries. We found out, that
there are not only two directions (on edge, laid flat), but three - through
the flakes. First it was pure chance. We had to divide bales in smaller
pieces for testing procedure. The best performance had a (piece of a) bale
on edge but measured through a flake.
In our efforts to optimize bales for the building-companies (Baustrohballen)
there was a second disadvantage of strawbales from the field: The different
length, which means more work at infill-systems, which means a higher price
for walls and roofs. The solution found by two companies in Austria was
pressing bales under norm-conditions: if you take the same amount of straw
for pressing the bales, you get bales with the same length and weight
(density). This was a precondition for certified (ÜA, CE,...) standard bales
as used for prefabricated walls by the building industry.
So we will use two kind of bales for different ranges of applications: The
standard bale (which in reality has no standard) from the field for
constructions on site (infill on building site) and the "Baustrohballen"
(which has to be a certified standard bale - each with the same length,
width, density, dryness, lambda-value...) for prefabricated houses.
Please understand that it was a lot of development and testing for these
companies, so I can't tell you more at this time. "Baustrohballen" will be
available this summer in Austria, lambda-value will be about 0,045 0,047
(truly and realistic). Bales are on edge, but pressed like flakes. No
tricks, just trying to understand straw and stalks. And accepting, that
bales are optimized for horse-stables, but there is still potential to
optimize it as building material.
asbn - austrian strawbale network
Österreichisches Netzwerk für Strohballenbau
3720 Ravelsbach, Baierdorf 6
Email: asbn at baubiologie...
> Hi Herbert,
> Sorry if I was wrong, but I was only forwarding (and translating) what
> Dirk Scharmer send me as late as May 10th, 2007.
> Could you share with us the exact dimensions of your tested 'special'
> straw bales as well as saying whether they were tested posed 'flat' or
> 'on edge'?
> Thank you
>> From: asbn <asbn at baubiologie...>
>> Peter, this is wrong...
>> These are not the official R-values for Germany. The official R-
>> Value for
>> usual strawbales in Germany and Austria is 0,045 W/mK.
>> These are the R-Values for "Baustrohballen", special bales tested
>> special circumstances.
>> And it is an old but wrong conclusion, that the worse R-values are
>> We developed and tested those special strawbales for the building-
>> (for prefabricated walls and roofs) in 2008/2009 again in Austria
>> and had
>> much better results in 2 different official testing-institutions:
>> 0,047 W/mK
>> (inluding the 20% addition) ? although there is no test-paper
>> available yet
>> (we are still optimizing...).
>> The difference between "normal" strawbales and "Baustrohballen" is the
>> testing-procedure according to EU-building-codes, but it is possible
>> press those building-bales for prefabrication in a whole different
>> way, than
>> Dirk did. It's all about pressing the bales in the best way.
>> So we will have CE-certified "Baustrohballen" with nearly the same
>> R-values as the R-values for normal strawbales in Austria and
>> Germany this
>> Best wishes, Herbert
>> asbn - austrian strawbale network
>> ?sterreichisches Netzwerk f?r Strohballenbau
>> 3720 Ravelsbach, Baierdorf 6
>> Email: asbn at baubiologie...
>>> Hi Andr?,
>>> Below the response from Dirk Scharmer of the German Straw Bale
>>> Building association FASBA, when I asked him to comment on the 0,045
>>> figure I had found on their site
>>> ). Dirk's basically saying that in Germany the official values to
>>> calculate with are 0,08 (for bales flat) and 0,052 (for bales on
>>> and that these figures are 20% higher than the measured ones because
>>> in Germany there's an obligation (for all natural fibre-based
>>> insulation) to add 20% to compensate for the fact that the lambda
>>> are done on dry material whereas in the real world relative humidity
>>> of 75-95% in the walls do mean that insulation values decrease. He
>>> finishes with saying that these official 'calculation' values are not
>>> as good as the Austrian ones, but more realistic (according to him).
>>> Hope this helps.
>>> Regards, Peter
>>> PS: their values are valid for densities 90-110kg/m3
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