[GSBN] R-values for cob, ideally documented

[Art Ludwig-Oasis Design]

Hello people—

I am working on getting our cob structures to pass Title 24 California Energy Efficiency requirements. Got this from Gord Baird:

> static heat flow of R 0.8 per inch, and a dynamic heat flow of R 2.0 per inch.   


Anyone else have anything to contribute on the topic of R-values for cob? R 1.25 per inch was mentioned at the West Coast Natural Building Conference... 

The % of straw made an obvious difference in insulation value when we did fire resistance testing, but we did not translate this to an R-value. We could have up to 50% straw by volume in the mix (a bucket of loose straw per bucket of sand+clay). 


Gord’s $0.02:
> The R22 to  R24 was full the whole  house actual performance… but we had some walls at a steady state condition, and others in a dynamic condition.
> There are two equally important numbers  a static heat flow of R 0.8 per inch, and a dynamic heat flow of R 2.0 per inch.   
> 
> Steady State:  Assuming that there is no sun then cob will act at r 0.8 (with pumice or without).   We had hoped the pumice would be more influential for insulation, but all it really provided was an additional R 0.2 over and above regular cob.  It did provide a 2 fold increase in compression strength.    Any cob wall in cloudy climates or north or shaded locations will act as a steady state performance -  our home the North wall acted like the steady state value.  We had hoped the pumice would be more influential for insulation, but all it really provided was an additional R 0.2 over and above regular cob.  
> 
> Dynamic State:  On the south wall, our 24 inch walls acted like R 40 due to the ability to readily accept and store the solar radiation… cob has a slower thermal radiation which means that even in colder climates like ours that the south wall is fairly useful as it can collect more energy than it can radiate  it away.     
> 
> Some of it is covered in this document   https://ecosenseliving.files.wordpress.com/2011/09/science-research-report_sept_1.pdf <https://ecosenseliving.files.wordpress.com/2011/09/science-research-report_sept_1.pdf>    
> 
> A coincidence to get your email today… I had someone want to speak to me about greywater… and they were from Los Angeles.   I sent them your way.    I recall you were moving (or  planning) on heading to the San Fran Bay area.   
> Cheers
> Gord Baird
> gord at eco-sense.ca <mailto:gord at eco-sense.ca>
> www.eco-sense.ca <https://eco-sense.ca/>
> 
> 3295 Compton Rd.
> Victoria, BC, V9E 1C8
> Phn: 250-478-2680

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sustainablesources.com/pipermail/gsbn/attachments/20180501/7cc61f05/attachment.htm>