[GSBN] Fwd: [nbne] R-value of compressed straw panels

[ejgeorge at riseup.net]

Hey again all. This question came up on the NBNE list from Tristan  
Roberts of BuildingGreen. Robert Riversong's response is included  
below Tristan's post, but I thought someone over here might also have  
more information on the purported Stramit lab test.

----- Forwarded message from tristan at buildinggreen.com -----


Hi,

Does anyone have insight into the R-value of compressed straw panels  
such as Stramit (currently produced in Texas) or Agriboard (no longer  
being produced)?

Stramit USA claims R-3.03/inch, and I have even seen press releases  
claiming R-3.35. However, the company can't produce a lab test to  
prove this to me, and there is history of R-value inflation in  
compressed straw, as this old EBN article talks about:

http://www.buildinggreen.com/auth/article.cfm/1998/1/1/Agriboard-s-Inflated-R-value-Claims/

I supposed there might be less convective loops in a compressed straw  
panel compared with a bale, but intuitively it's hard for me to  
picture how compressed straw has higher R-value.

It's probably a longshot, but I wondered if anyone has any insight (or  
maybe you know someone who might). Also, if you have any recent  
experience with Stramit, I'd like to talk with you.

thanks!

Tristan


____________
Tristan Roberts
Editorial Director
BuildingGreen, Inc.
http://www.BuildingGreen.com
http://www.LEEDuser.com

(802) 257-7300 x121
tristan at buildinggreen.com

-----------end forwarded message -----------

Robert's reply:

Loose fibrous materials often increase in R-value per inch with  
increased density - up to a point of diminishing returns - and I have  
no reason to doubt that compressed straw would be more insulative than  
straw bales.

Loose-fill fiberglass, for instance, is about R-2.5/inch, while  
fiberglass batts, which used to be about R-3.14/inch for standard R-11  
batts, were increased to R-13 (3.7/inch) in "high-density batts", and  
semi-rigid fiberglass board as well as dense-pack Spider is about  
R-4/inch.

Similarly, loose fill cellulose is about R-3.4/inch at 1.4 pcf  
density, while dense-pack cellulose at 3+ pcf can be as much as  
R-3.8/inch.

But the density range that Stramit specs of 15.6-40.5 pcf puts it at  
about the same density range as solid wood, which is about  
R-1.25/inch. So I also question their claim of R-3.35/inch.