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GSBN:CalifoRnian values (was re: from the Crest list)



Rocky et al;

I don't recall the specifics of the CEC tests at the ATI labs but I do recall that at the time, I was shaking my head at the manner in which the test panels were prepared before being presented to the ATI people for testing.

I have vague memories of things like foam insulation board being jammed into cracks at the perimeter by the ATI people *during* the tests, presumably to reduce the haemorrhaging so that their results wouldn't make them look incompetent as a testing facility. (ie the GIGO syndrome)

I alos have vague memories of meaningless moisture content readings being taken (I think that it was of bales that weren't even inside of the test panel), while ignoring the wet condition of the bales in the actual test panel which hadn't been allowed to dry out properly after stucco application.

It was therefore no surprise that the CEC/ATI tests yielded disappointingly low R-values for straw but even more disappointing was the fact that the CEC chose to accept the test results as being representative of the insulating properties of straw bales.

There is no doubt in my mind as to the accuracy of the thermal resitivity values that JoE McCabe's testing provided, as they agree perfectly with the theoretical value that would be yielded by the equation used to estimate thermal conductivity (k) in the absence of data:

                    k = 0.281*Exp((0.0268*density)

(note that the above equation will yield a value that is dead-nuts in the middle of the two values that JoE provided in which he accounted for fibre orientation WRT heat flow... which also makes sense because the equation does not have a modifier for bale orientation)

The Sandia lab resistivity test results (although of bales of lower density than that used by JoE in his testing) would seem to further confirm that the CEC/ATI thermal resistance values are seriously flawed.

ie The ASHRAE values for the thermal resistivity of materials (presumably derived from testing of the materials under lab conditions) is regularly used to estimate the nominal thermal resistance of building assemblies for permit purposes etc. so why should there be a double standard for straw bales ?

Clearly, it was the process (ie of the panel preparation, not of the ATI testing) which was flawed and it would seem to make sense that the tests should be re-done (making the necessary changes each time of course... they say that one of the signs of insanity is repeating the same actions over and over again expecting a different result each time) until the thermal resistance of the test walls approaches the values that are predicted by JoE's resistivity values.

Aside from the issue of respectability for strawbale housing (ie why would anyone go to the trouble of doing plastered SB walls to achieve a mere R-30 when better than R-30 can be easily achieved in a thinner and readily-accepted-by-Conventionaldumb stick-framed wall ?), one would think that there would be more pragmatic consequences, such as in the reduction of the sizing of Code-required auxiliary heating (and cooling ?) systems, possibly even eliminating them in some instances, ultimately saving the homeowner's financial resources and perhaps more importantly, the planet's resources.

--- * ---
Robert W. Tom
Kanata, Ontario, Canada
rw_tom@...

please visit:  http://www.theHungerSite.com daily

Date: 6 May 2003 23:58:40 -0500
From: stoneandstraw@...
Subject: RE: From the Crest list


In California, the accepted R-value (for compliance with the state building
standards) is R-30.  That was based on a the results of a number of tests.
One that I managed while at the California Energy Commission (CEC), two at
Oak Ridge National Lab, the tests that Joe McCabe did, and testing that
Sandia Labs did. Every test had issues, and didn't all test the same thing.
For example, McCabe and Sandia tested straw bales, while the other tests
were of straw bale walls.
[snip]

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