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GSBN: Digest for 10/9/04

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-> RE: GSBN:Danish Testing on SB walls
     by jfstraube@...


Date: 9 Oct 2004 09:42:19 -0600
From: jfstraube@...
Subject: RE: GSBN:Danish Testing on SB walls

Hi Chris!

I donwnloaded the wonderful reports and looked through them, including
the Danish ones (I can read a bit of it)
I am too busy to write an article, but for what its worth, some comments
They found that the thermal conductivity of straw was in line with
measurements (k=.052-0.056) which is R2.75/inch in Murrican units

The measured heat flow through the full size bale wall, however, was
lower than predicted from the material conductivity measurements, ie.,
an 18" wall did not have an R value of 18*2.75.  In fact it was much
lower -- they got about R28-R30.  This is still very good, but it could
be better, up to R45 or R50.  The reason for the discrepancy is
believed, on good evidence, to be airflow looping around within the
bales. This reinforces the need to use well packed bales with no airgaps
anywhere -- packed full of clay straw or highly compacted straw.

They tested full size walls with warm humid conditions on the inside and
cool outside conditions showed that after several months the MC of the
straw could rise to 20% or so but would dry quickly. (My note, this is
what computer models tell us and what we have seen in monitoring).  They
also showed that allowing airleakage from inside to out under these
conditions will cause dangerous increases in MC.  They therefore
recommend (duh) that the interior layter be made as airtight as
possible. The lime plaster wall seemed to exhibit lower MC, which is
likley because the permeance tests showed it was less permeable than the
clay (eg less vapor got into the lime plaster wall from the interior).

They tested ten types of lime and earth plaster, with and without water
repellent treatments.  The vapor permeance of these ranged from about
300 to 650 metric perms (divide by 57.3 to get US perms) for a sample 40
mm thick.  This means they are not vapor barriers by code definitions
and do allow significant drying -- thinner layers would allow more to
pass through but are difficult to build. These are essentially identical
results to what we got when we tested them.  I have not dug deep into
the details yet.

Straw itself has a high vapor permeance (no surprise) about similar to
the equivalent thickness of still air.  Essentially vapor goes through
SB like shit through a goose. 

They tested walls with a high load on them for 2 years.  Settling was
limited to about 3 mm (surprisingly little), with sizeable variations
due to relative humdity swings (not a surprise)
Hope this helps a bit

John Straube
School of Architecture and Dept of Civil Engineering
University of Waterloo
Waterloo, Canada
<a  target="_blank" href="http://www.civil.uwaterloo.ca/beg";>http://www.civil.uwaterloo.ca/beg</a>

- -----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Chris
Sent: October 8, 2004 13:07
Subject: Re: GSBN:Danish Testing on SB walls

Hello GSBN'ers,

I have just downloaded the english package regarding the Danish straw
bale tests, as drawn to our attention by the ever-wonderful Lars.

Not being a science guy, I'm not sure how to interpret some of the
results, since I don't understand the terminology, nor do I have any
basis for comparison to other materials and tests.

But I would dearly love to include an article about these test results
in The Last Straw. Does anybody on this list feel like putting these
results into context and presenting them as an article for TLS?

Please let me know!


>Dear Marcus et al.
>The Danish sb-testprogramme has produced several results now available 
>via the internet. Thanks to a lot of work by Jorgen Munch-Andersen
>   MSc (CivEng), PhD, Head of Department
>   +45 4574 2388
>   jma@...
>the results are also partly available in English:
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/jma_slides_halmhuse.pdf";>http://www.by-og-byg.dk/download/pdf/jma_slides_halmhuse.pdf</a>
>The test reports (in Danish) are available via the following links:
>- fire test of clay as a surface cover material: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/pg10809.pdf";>http://www.by-og-byg.dk/download/pdf/pg10809.pdf</a>
>- 30min fire test of clay plastered non-loadbearing sb-wall: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/pg10810.pdf";>http://www.by-og-byg.dk/download/pdf/pg10810.pdf</a>
>- air-sound-insulation of clay plastered non-loadbearing sb-wall: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/p870072.pdf";>http://www.by-og-byg.dk/download/pdf/p870072.pdf</a>
>- capillary hight rise of mussell shells, three densities: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/2001-02-21.pdf";>http://www.by-og-byg.dk/download/pdf/2001-02-21.pdf</a>
>- organic and microbial dust as a healtrisk in strawbale building: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/amislutrapport.pdf";>http://www.by-og-byg.dk/download/pdf/amislutrapport.pdf</a>
>- water vapour transmission properties of clay plaster with various 
>surface treatments / additives: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/423-8a.pdf";>http://www.by-og-byg.dk/download/pdf/423-8a.pdf</a>
>- water vapour transmission properties of straw 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/423-8b.pdf";>http://www.by-og-byg.dk/download/pdf/423-8b.pdf</a>
>- moisture accumulation of sb-walls plastered with clay plaster on the 
>inside (warm side) and clay plaster or lime plaster on the outside 
>(cold side): <a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/423-8c.pdf";>http://www.by-og-byg.dk/download/pdf/423-8c.pdf</a>
>- settling of non-loadbearing and loadbearing sb-walls after two 
>moisture cycles: <a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/423-8d.pdf";>http://www.by-og-byg.dk/download/pdf/423-8d.pdf</a>
>- thermal insulation of earthplastered sb-wall, bale lying flat: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/55650-34.pdf";>http://www.by-og-byg.dk/download/pdf/55650-34.pdf</a>
>- thermal insulation of earthplastered sb-wall, bale on edge: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/55650-35.pdf";>http://www.by-og-byg.dk/download/pdf/55650-35.pdf</a>
>- thermal insulation of non plastered straw bale, on edge, flat, two 
>different densities: <a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/danak.pdf";>http://www.by-og-byg.dk/download/pdf/danak.pdf</a>
>- thermal insulation of mussell shells, three different densities: 
><a  target="_blank" href="http://www.by-og-byg.dk/download/pdf/danak.pdf";>http://www.by-og-byg.dk/download/pdf/danak.pdf</a>
>Please pass on, and enjoy your reading.
>Best regards,
>Lars Keller
>----- Original Message -----
>From: echoventures@...
>To: strawbale@...
>Sent: Wednesday, September 22, 2004 3:48 PM
>Subject: [Strawbale]Fire Testing on SB walls
>>  Help,
>>  I'm building a SB house in Hungary and after getting permission for 
>>a wooden framed cob house and applying for the modification of the 
>>building permit to Sb walls, I have been turned down on the grounds of

>>fire risk.
>>  Does anyone know of any certificates, tests or publications which 
>>documents fire testing on strawbale walls in Europe and where I might 
>>find them?  American/Canadian tests are no good for the building 
>>department here.  Or any loopholes to get around this law?
>>  Thanks,
>>  Marcus
>>  ____________________________________________________
>>      European strawbale building discussion list
>>  Send all messages to:
>>  Strawbale@...
>>  Archives, subscription options, etc:  
>> <a  target="_blank" href="http://amper.ped.muni.cz/mailman/listinfo/strawbale";>http://amper.ped.muni.cz/mailman/listinfo/strawbale</a>
>>  ____________________________________________________
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Chris Magwood / Camel's Back Straw Bale Construction
<a  target="_blank" href="http://www.strawhomes.ca";>http://www.strawhomes.ca</a>

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The Last Straw Journal?
You should!
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GSBN is an invitation-only forum of key individuals and representatives
of regional straw construction organizations. The costs of operating
this list are underwritten by The Last Straw Journal in exchange for use
of the GSBN as an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list,
send email to GSBN@...HELP in the SUBJECT line.

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