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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>
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<div><img apple-inline="yes" id="9B8B7B68-89A8-4030-BE1A-FE62051B8F53" height="913" width="730" apple-width="yes" apple-height="yes" src="cid:94635A9B-5E89-4C25-9492-DF86AF4F7D50@gateway.2wire.net"><br>
On Jan 26, 2015, at 3:35 PM, Graeme North <<a 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 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 <bruce@ecobuildnetwork.org> 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 <mfhammer@pacbell.net> wrote:<br>
<br>
Hello Lance,<br>
<br>
A delayed reply on this.<br>
<br>
A company in California called Oryzatech (http://www.oryzatech.com/) 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: d2bdesign@gmail.com<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" <sabale@bigpond.com> 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 [mailto:torokenterprise@me.com] <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>
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<br>
<div apple-content-edited="true">John F Straube<br>
<a href="mailto:jfstraube@uwaterloo.ca">jfstraube@uwaterloo.ca</a><br>
www.JohnStraube.com<br>
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