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It is also perhaps worth noting that Stramit panels (according to
their data <a class="moz-txt-link-freetext" href="http://www.stramit.co.uk/content/view/13/30/">http://www.stramit.co.uk/content/view/13/30/</a>) have a
standard density of 350kg/m3 and a thermal conductivity of 0.102
W/mk (R=0.5882m<sup>2</sup>kW for 58mm thick panel).<br>
<br>
Andy<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 12:31, Andrew Thomson wrote:
<blockquote cite="mid:54C7850C.3090104@bath.ac.uk" type="cite">
<meta content="text/html; charset=ISO-8859-1"
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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 moz-do-not-send="true"
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:part2.08080309.01000403@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:part3.06010904.02030408@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
moz-do-not-send="true" 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 moz-do-not-send="true"
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
moz-do-not-send="true" 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 moz-do-not-send="true"
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
moz-do-not-send="true" 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 moz-do-not-send="true"
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>
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<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 moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="http://www.JohnStraube.com">www.JohnStraube.com</a><br>
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