<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
Hi All,<br>
<br>
I have recently joined as a posting member to GSBN so thought I'd
add to the conversation on thermal conductivity of straw at
different densities. Colleagues of mine at the University of Bath
have done some testing in this area and published the findings -
details here: <a class="moz-txt-link-freetext" href="http://opus.bath.ac.uk/30137/">http://opus.bath.ac.uk/30137/</a> <br>
<br>
The paper includes a graph (copied below) of tests done at Bath Uni
and others, including FASBA. The results suggest that below a
density of 120kg/m3 thermal conductivity is less sensitive to
deceasing density than might be expected. It appears that the
thermal conductivity of straw is actually more sensitive to the
temperature of the straw and it's moisture content. Hope this is of
interest.<br>
<br>
Cheers, Andy<br>
<br>
<img src="cid:part1.05020207.08080301@bath.ac.uk" alt=""
height="358" width="541"><br>
<br>
<pre class="moz-signature" cols="72">Dr Andrew Thomson MEng PhD
BRE Centre for Innovative Construction Materials
Dept of Architecture and Civil Engineering
University of Bath
01225 386621</pre>
<br>
On 27/01/2015 00:25, John Straube wrote:
<blockquote
cite="mid:EFD6D045-800C-4C34-87B7-EC53B3CA9C6C@uwaterloo.ca"
type="cite">
<meta http-equiv="Content-Type" content="text/html;
charset=ISO-8859-1">
I am not sure if I can send images but I am trying
<div>If you are at high density (soil, wood etc), then reducing
density increases R-value (that is decreases thermal
conductivity). If you are at very low density, then decreasing
density decreases R-value</div>
<div>The plot below is made up of many many materials.</div>
<div>The vertical axis is conductivity and the horizontal axis is
density.</div>
<div>You can see the lowest conductivity / highest R-value per
inch, occurs around 30 to about 125 kg/m3. (2 to 8 pcf). The
obvious deviation around 30-40 kg/m3 (2-2.5 pcf) is due to foams
filled with gases other than air (Freon etc).</div>
<div><br>
</div>
<div><br>
</div>
<div><img apple-inline="yes"
id="9B8B7B68-89A8-4030-BE1A-FE62051B8F53" apple-width="yes"
apple-height="yes"
src="cid:part2.03070807.06090204@bath.ac.uk" height="913"
width="730"><br>
On Jan 26, 2015, at 3:35 PM, Graeme North <<a
moz-do-not-send="true" href="mailto:graeme@ecodesign.co.nz">graeme@ecodesign.co.nz</a>>
wrote:<br>
<br>
<blockquote type="cite">thanks John - I knew that there were at
least some research answers out there.<br>
Reminds me once again how lucky we are to have such wonderful
researchers and scientists contributing so willingly to this
group.<br>
<br>
Graeme<br>
<br>
<br>
<br>
On 27/01/2015, at 9:06 AM, Graeme North <<a
moz-do-not-send="true" href="mailto:graeme@ecodesign.co.nz">graeme@ecodesign.co.nz</a>>
wrote:<br>
<br>
<blockquote type="cite">Bruce<br>
<br>
Interesting<br>
<br>
My observation of R values of different materials over many
years , (esp with earthen materials mixed with aggregates
of different densities ranging from stone to straw),
generally points to an almost linear and direct inverse
correlation between density and R value, whereby R value
increases as density decreases - so am a bit puzzled by this
discussion<br>
Unless the k value for straw is significantly better than
that of still air?<br>
And is there really any significant convective flow of air
within a straw bale, plastered or not? <br>
Has anyone got any figures?<br>
<br>
More questions than answers<br>
<br>
<br>
Graeme <br>
<br>
<br>
On 25/01/2015, at 12:43 PM, Bruce EBNet
<a class="moz-txt-link-rfc2396E" href="mailto:bruce@ecobuildnetwork.org"><bruce@ecobuildnetwork.org></a> wrote:<br>
<br>
<blockquote type="cite"><br>
Let me jump right in with a couple of things to add to
Martin’s post:<br>
<br>
1) I have been a board member and partial owner of Stak
Block for ten years, so speak with a bit of certainty when
I basically agree with Martin; the thermal tests were a
bit funky (an undergrad engineering student doing his
first unguarded hot plate test at Cal Polytechnic
University in California). I emphatically agree that we
don’t know, and would like to know, the optimal density of
a straw bale (or block) for insulating purposes. My
gut sense is that it will be denser than conventional
bales, maybe even as dense as Peter’s
super-compressed bales.<br>
<br>
2) The widely-accepted R-values Martin quotes are
averaged values taken across a plastered bale
section, including the thickness of plaster. A plastered
straw bale wall is an intricate composite assembly that
achieves far better structural, fire and thermal
properties than the sum of its constituent parts. That
is, a straw bale by itself probably has much less than
R1.3 or 2 as described because there is no plaster to
arrest convective air flow across the assembly.<br>
<br>
3) When we ran the straw bale research program 14 years
ago we did look at super compressed bales, but
only glancingly. If someone contemplates using them in a
building, they should consider not only R-value, but
also bond of plaster to the face of straw (is it better?
worse?).<br>
<br>
cheers everyone,<br>
<br>
Bruce King<br>
<br>
(415) 987-7271<br>
BuildWellLibrary.org<br>
<br>
<BWL logo for email.jpg><br>
<br>
<blockquote type="cite" class="">On Jan 24, 2015, at 3:12
PM, martin hammer <a class="moz-txt-link-rfc2396E" href="mailto:mfhammer@pacbell.net"><mfhammer@pacbell.net></a> wrote:<br>
<br>
Hello Lance,<br>
<br>
A delayed reply on this.<br>
<br>
A company in California called Oryzatech
(<a class="moz-txt-link-freetext" href="http://www.oryzatech.com/">http://www.oryzatech.com/</a>) has for years been in the
development of manufacturing a compressed straw block
called Stak Block (see attached fact sheet). They have
made claims of an R-value of 3.89/inch (see
2nd attachment). I like this product in many ways and
think it has tremendous potential. However I’m skeptical
of the R-value claim because I haven’t seen a bona fide
testing report, and it’s hard to believe the R-value of
a compressed straw block would double compared to a
typical straw bale. <br>
<br>
The R-value for a straw bale, from the most trusted test
in the US (the 1998 guarded hot-box test at Oak Ridge
National Laboratory) is R 1.3/inch laid flat and
R-2/inch on-edge. This is still a matter of debate, but
this is what the testing showed. The difference in
R-value per inch is explained by the predominant
orientation of the straw in a bale (or at least in the
bales tested). <br>
<br>
Though counterintuitive, it’s possible a compressed bale
would have a higher unit R-value than a normal bale, if
by being compressed it confines more air spaces. Thermal
resistance is all about maximizing the number of
confined air spaces and reducing thermal bridging.
Regarding the latter, I would expect the thermal
bridging across a bale would increase when it
is compressed. There is likely an optimum density for
straw that will yield the highest unit R-value, but this
has yet to be researched and demonstrated.<br>
<br>
Another point of thermal resistance comparison is
polyiscocyanurate, which has the highest unit R-value of
any foam plastic insulation at R 5.6/inch. For years
polyiso claimed an R-value of 6.0/inch (or higher), but
it was adjusted downward a year ago under new testing
protocol. (Sorry to bring a distasteful petrochemical
insulation into the discussion of natural insulation! It
does have quite an ability to insulate however.)
Fiberglass insulation is said to be R3.1 to R4/inch
(material only, not including thermal bridging of
framing).<br>
<br>
Regarding density, from the Stak Block fact sheet, the
1’x1’x2’ blocks weigh 30 pounds. So they are 15 pcf or
240 kg/m3. Peter’s compressed bales are 468 kg/m3. Those
are quite dense, almost twice as dense as the Stak
Blocks, and 4 times as dense as a typical straw bale.
Even if you trust the R-values I’m stating for a typical
straw bale and for a Stak Block, I don’t know how
you would reliably extrapolate them to a denser block.
The obvious answer is to subject Peter’s blocks to a
reliable test.<br>
<br>
You or Peter Torok might contact the co-founder of the
company Stak Block to better understand nature of their
blocks and their tested thermal resistance. Ben
Korman: <a class="moz-txt-link-abbreviated" href="mailto:d2bdesign@gmail.com">d2bdesign@gmail.com</a><br>
<br>
Speaking of Peter, was he ever seconded and brought into
GSBN?<br>
<br>
I hope this is helpful.<br>
<br>
Best.<br>
<br>
Martin<br>
<br>
<br>
Martin Hammer, Architect<br>
1348 Hopkins St.<br>
Berkeley, CA 94702<br>
<br>
<br>
On 1/1/15 7:41 PM, "Lance Kairl"
<a class="moz-txt-link-rfc2396E" href="mailto:sabale@bigpond.com"><sabale@bigpond.com></a> wrote:<br>
<br>
<blockquote class="" type="cite">Any one have an idea
on R value for super compressed export Bales.<br>
<br>
Any info will be passed on ,<br>
Although I should nominate Peter to join the list.<br>
Is there a seconder out there, and then I will fill
you in on his good works.<br>
<br>
Regards lance kairl<br>
Hosue of Bales.<br>
<br>
<br>
From: Peter Torok [<a class="moz-txt-link-freetext" href="mailto:torokenterprise@me.com">mailto:torokenterprise@me.com</a>] <br>
Sent: Thursday, 11 December 2014 1:13 PM<br>
To: House of Bales<br>
Subject: R value<br>
<br>
<br>
G'day lance, <br>
<br>
<br>
As discussed these bales are very well compacted, the
dimensions are 400x500x480 45kg or 400x500x240 22kg
baled at less than 12% moisture and compressed at 5000
psi. If the bales were sitting on the 400 side, the
straw runs horizontal. I inquired about lowering the
pressure and he felt the integrity of the bale would
be jeopardized, but more pressure can still be
applied. I hope that is enough information to
calculate a rough R value for both thickness', I look
forward to hearing what you come up with. Thanks for
helping me out with this, it's very much appreciated.<br>
<br>
I have found old studies from around 2003 that
calculate between R1.4-2.4 US measure / inch<br>
<br>
This R1.4 – 2.4 relates to standard housing bales,<br>
Export ones may equate to the R value for Timber??<br>
<br>
Regards Pete Torok<br>
<br>
Earth Wood & Straw<br>
<br>
0411 304 794 <tel:0411%20304%20794> <br>
<br>
_______________________________________________<br>
GSBN mailing list<br>
<a class="moz-txt-link-abbreviated" href="mailto:GSBN@sustainablesources.com">GSBN@sustainablesources.com</a><br>
<a class="moz-txt-link-freetext" href="http://sustainablesources.com/mailman/listinfo.cgi/GSBN">http://sustainablesources.com/mailman/listinfo.cgi/GSBN</a><br>
</blockquote>
<StakBlockFacts.png><StakBlockR-Value.png>_______________________________________________<br>
GSBN mailing list<br>
<a class="moz-txt-link-abbreviated" href="mailto:GSBN@sustainablesources.com">GSBN@sustainablesources.com</a><br>
<a class="moz-txt-link-freetext" href="http://sustainablesources.com/mailman/listinfo.cgi/GSBN">http://sustainablesources.com/mailman/listinfo.cgi/GSBN</a><br>
</blockquote>
<br>
_______________________________________________<br>
GSBN mailing list<br>
<a class="moz-txt-link-abbreviated" href="mailto:GSBN@sustainablesources.com">GSBN@sustainablesources.com</a><br>
<a class="moz-txt-link-freetext" href="http://sustainablesources.com/mailman/listinfo.cgi/GSBN">http://sustainablesources.com/mailman/listinfo.cgi/GSBN</a><br>
</blockquote>
<br>
_______________________________________________<br>
GSBN mailing list<br>
<a class="moz-txt-link-abbreviated" href="mailto:GSBN@sustainablesources.com">GSBN@sustainablesources.com</a><br>
<a class="moz-txt-link-freetext" href="http://sustainablesources.com/mailman/listinfo.cgi/GSBN">http://sustainablesources.com/mailman/listinfo.cgi/GSBN</a><br>
</blockquote>
<br>
_______________________________________________<br>
GSBN mailing list<br>
<a class="moz-txt-link-abbreviated" href="mailto:GSBN@sustainablesources.com">GSBN@sustainablesources.com</a><br>
<a class="moz-txt-link-freetext" href="http://sustainablesources.com/mailman/listinfo.cgi/GSBN">http://sustainablesources.com/mailman/listinfo.cgi/GSBN</a><br>
</blockquote>
<br>
<div apple-content-edited="true">John F Straube<br>
<a moz-do-not-send="true" href="mailto:jfstraube@uwaterloo.ca">jfstraube@uwaterloo.ca</a><br>
<a class="moz-txt-link-abbreviated" href="http://www.JohnStraube.com">www.JohnStraube.com</a><br>
<br>
<br>
</div>
<br>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
GSBN mailing list
<a class="moz-txt-link-abbreviated" href="mailto:GSBN@sustainablesources.com">GSBN@sustainablesources.com</a>
<a class="moz-txt-link-freetext" href="http://sustainablesources.com/mailman/listinfo.cgi/GSBN">http://sustainablesources.com/mailman/listinfo.cgi/GSBN</a>
</pre>
</blockquote>
</body>
</html>