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In several of the scientific tests run at universities, it has been shown that construction-quality bales do not get any significant compression, as individual bales, when the whole wall is pre-compressed. Pre-compressing a wall mostly removes or reduces spaces
between the bales, which is why I prefer using a different term, such as "wall compaction". Thermal imaging cameras have shown that there is greater heat flow between the bales, where the spaces/cracks between the bales have been stuffed with loose straw.
Therefore, reducing the size of the spaces between bales can improve the thermal performance. Builders who cut the strings on the bales seek to reduce the spaces between bales by a different method, which I also believe to be effective.
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<div>Derek</div>
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<div>On Mar 12, 2014, at 5:38 AM, Tom Peeters wrote:</div>
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<div><span>Hi Herbert,</span></div>
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<span>I know the differences in U-value and I know the insulation depends on the weight of the bale, but I was referring to the extra comprenssion when placed in a wall: are there tests that show a significant change in U-value - for the better or the worse
- when there is an extra compression of the bales in the wall?</span></div>
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<span>I ask this because the insulation value from a bale comes - at least partly - from the air that is contained in the hollow straws, so I wonder if (to much) compression wouldnt squash the hollow straws and thus make the bales insulate less?</span></div>
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<span>kind regards</span></div>
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<div>Tom</div>
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<div dir="ltr"><font size="2" face="Arial">On Wednesday, March 12, 2014 12:01 PM, asbn <<a href="mailto:asbn@baubiologie.at">asbn@baubiologie.at</a>> wrote:<br>
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<div>Dear Tom and Stefano
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<div>Yes there are tests for different weights, and lambda depends on the compression.</div>
<div>GrAT (TU Vienna) as well as Waldland made series of tests, showing that the ideal weight for a good insulation-value </div>
<div>lies between 90 and 120 kg/m3.</div>
<div>For a standard small bale this means divided by 7,6, so a small bale should weigh between 12 and 15 kg.</div>
<div>Other way to find out if the bale is usable: if you can easily move the 2 strings together, it is too floppy.</div>
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<div>And there is a different insulation-value for</div>
<div>bales on edge: lambda = 0,05(2)</div>
<div>bales laid flat: lambda = 0,085</div>
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<div>As mainly bales laid flat are compressed (like in loadbearing construction), </div>
<div>these walls have - although compressed - a worse thermal performance (U-value) than bales on edge,</div>
<div>which are normally used in infill-construction-systems. </div>
<div><br clear="none">
<div><span class="yiv0942371164Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Verdana; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; font-size: medium;"></span>
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<div>all the best</div>
<div>Herbert Gruber</div>
<div>-----------------</div>
<div>asbn - austrian strawbale network</div>
<div>3720 Ravelsbach, Baierdorf 6</div>
<div>Tel. 02958-83640</div>
<div><a rel="nofollow" shape="rect" ymailto="mailto:asbn@baubiologie.at" target="_blank" href="mailto:asbn@baubiologie.at">asbn@baubiologie.at</a></div>
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<div>Am 12.03.2014 um 11:27 schrieb permacultura la boa:</div>
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<div dir="ltr">I do not know if is there any 'scientific' test, I have only to share my experience: ten years practicing & teaching and 46 sb building realized.<br clear="none">
T<span id="yiv0942371164result_box" lang="en"><span class="yiv0942371164hps">ests many times are</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164hps">contradictory</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164hps">and</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164hps">often</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164hps">fail
when they want to put</span><span class="yiv0942371164hps"><span class="yiv0942371164Apple-converted-space"> </span>natural materials</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164hps">into</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164hps">a
table</span></span>...<br clear="none">
stefano<br clear="none">
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Date: Wed, 12 Mar 2014 03:01:46 -0700<br clear="none">
From:<span class="yiv0942371164Apple-converted-space"> </span><a rel="nofollow" shape="rect" ymailto="mailto:tompeeters13@yahoo.com" target="_blank" href="mailto:tompeeters13@yahoo.com">tompeeters13@yahoo.com</a><br clear="none">
Subject: Re: [Strawbale] compressing or not<br clear="none">
To:<span class="yiv0942371164Apple-converted-space"> </span><a rel="nofollow" shape="rect" ymailto="mailto:casadipaglia@hotmail.com" target="_blank" href="mailto:casadipaglia@hotmail.com">casadipaglia@hotmail.com</a>;<span class="yiv0942371164Apple-converted-space"> </span><a rel="nofollow" shape="rect" ymailto="mailto:jure.pozar@gmail.com" target="_blank" href="mailto:jure.pozar@gmail.com">jure.pozar@gmail.com</a>;<span class="yiv0942371164Apple-converted-space"> </span><a rel="nofollow" shape="rect" ymailto="mailto:strawbale@amper.ped.muni.cz" target="_blank" href="mailto:strawbale@amper.ped.muni.cz">strawbale@amper.ped.muni.cz</a><br clear="none">
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<div>Are there scientific tests that show that compressing a wall actually benefits the insulation value or that provide a maximum compression level?</div>
<div></div>
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<div>kind regards </div>
<div>Tom Peeters</div>
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<div dir="ltr"><font face="Arial" size="2">On Wednesday, March 12, 2014 10:06 AM, permacultura la boa <<a rel="nofollow" shape="rect" ymailto="mailto:casadipaglia@hotmail.com" target="_blank" href="mailto:casadipaglia@hotmail.com">casadipaglia@hotmail.com</a>>
wrote:<br clear="none">
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<div dir="ltr"><span id="yiv0942371164ecxyiv4227905776result_box" lang="en"><span class="yiv0942371164ecxyiv4227905776hps">From</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">my personal experience</span><span>,
both</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">in load bearing</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">than</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">in
post</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">and beam</span><span>, compression (and well done!) is essential</span><span class="yiv0942371164ecxyiv4227905776hps"></span><span class="yiv0942371164ecxyiv4227905776hps"></span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">for</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">static,</span><span><span class="yiv0942371164Apple-converted-space"> </span>structural
and</span><span class="yiv0942371164Apple-converted-space"> </span><span class="yiv0942371164ecxyiv4227905776hps">insulation<span class="yiv0942371164Apple-converted-space"> </span></span></span><span id="yiv0942371164ecxyiv4227905776result_box" lang="en"><span class="yiv0942371164ecxyiv4227905776hps"><span id="yiv0942371164ecxyiv4227905776result_box" lang="en"><span class="yiv0942371164ecxyiv4227905776hps">reasons</span><span></span></span>.</span></span><br clear="none">
Stefano<br clear="none">
<a rel="nofollow" shape="rect" target="_blank" href="http://www.laboa.org/">www.laboa.org</a><br clear="none">
<br clear="none">
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<div class="yiv0942371164ecxyiv4227905776yqt6909358950" id="yiv0942371164ecxyiv4227905776yqtfd77024">
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Date: Tue, 11 Mar 2014 12:59:56 +0100<br clear="none">
From:<span class="yiv0942371164Apple-converted-space"> </span><a rel="nofollow" shape="rect" ymailto="mailto:jure.pozar@gmail.com" target="_blank" href="mailto:jure.pozar@gmail.com">jure.pozar@gmail.com</a><br clear="none">
To:<span class="yiv0942371164Apple-converted-space"> </span><a rel="nofollow" shape="rect" ymailto="mailto:strawbale@amper.ped.muni.cz" target="_blank" href="mailto:strawbale@amper.ped.muni.cz">strawbale@amper.ped.muni.cz</a><br clear="none">
Subject: [Strawbale] compressing or not<br clear="none">
<br clear="none">
<font face="Calibri">Dear all,<br clear="none">
<br clear="none">
I have a fairly simple question? Is it necessarily to compress a wall of strawbales which is supporting only itself. It is basicaly an exterior strawbale wrapper of an existing brick wall. As far as I can remember Kuba didn`t compress strawbales on his workshop
on ESBG in 2011. Can the strawbales sit-down after some years due to its weight and make cracks to the exterior clay plaster? The height of the wall is less than 3 meters.<br clear="none">
<br clear="none">
Cheers<span class="yiv0942371164Apple-converted-space"> </span><br clear="none">
<br clear="none">
Jure<br clear="none">
</font><br clear="none">
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