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<TITLE>Re: [GSBN] R value export straw blocks?</TITLE>
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<FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Very revealing graph John. Thank you. <BR>
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With the optimal density of most materials being in the 2 to 8 pcf range (for highest thermal resistance) this implies that the typical straw bale (in the 6.5 – 9 pcf range) is already at or near its optimal density. Any thoughts? Also, I wonder about a straw bale filled with freon or argon. Hmmm . . .<BR>
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Martin<BR>
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On 1/26/15 4:25 PM, "John Straube" <<a href="jfstraube@uwaterloo.ca">jfstraube@uwaterloo.ca</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>I am not sure if I can send images but I am trying <BR>
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<BR>
The plot below is made up of many many materials.<BR>
The vertical axis is conductivity and the horizontal axis is density.<BR>
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).<BR>
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<IMG src="cid:3505140734_49251003" ><BR>
On Jan 26, 2015, at 3:35 PM, Graeme North <<a href="graeme@ecodesign.co.nz">graeme@ecodesign.co.nz</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>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>
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Graeme<BR>
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On 27/01/2015, at 9:06 AM, Graeme North <<a href="graeme@ecodesign.co.nz">graeme@ecodesign.co.nz</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Bruce<BR>
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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>
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<BR>
Graeme <BR>
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On 25/01/2015, at 12:43 PM, Bruce EBNet <<a href="bruce@ecobuildnetwork.org">bruce@ecobuildnetwork.org</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'><BR>
Let me jump right in with a couple of things to add to Martin’s post:<BR>
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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>
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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>
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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>
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cheers everyone,<BR>
<BR>
Bruce King<BR>
<BR>
(415) 987-7271<BR>
BuildWellLibrary.org<BR>
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<BWL logo for email.jpg><BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>On Jan 24, 2015, at 3:12 PM, martin hammer <<a href="mfhammer@pacbell.net">mfhammer@pacbell.net</a>> wrote:<BR>
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Hello Lance,<BR>
<BR>
A delayed reply on this.<BR>
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A company in California called Oryzatech (<a 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>
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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>
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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>
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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 href="d2bdesign@gmail.com">d2bdesign@gmail.com</a><BR>
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Speaking of Peter, was he ever seconded and brought into GSBN?<BR>
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I hope this is helpful.<BR>
<BR>
Best.<BR>
<BR>
Martin<BR>
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<BR>
Martin Hammer, Architect<BR>
1348 Hopkins St.<BR>
Berkeley, CA 94702<BR>
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On 1/1/15 7:41 PM, "Lance Kairl" <<a href="sabale@bigpond.com">sabale@bigpond.com</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Any one have an idea on R value for super compressed export Bales.<BR>
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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>
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From: Peter Torok [<a 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>
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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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John F Straube<BR>
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