[Cob] Thermal Mass and R-value

[Damon Howell]

	There's no measurement for thermal mass is what that website is  
saying. The research is in its infancy and there's a lot of people  
throwing around "effective R-value" when there's no standard. Codes  
do seem to want low U-value and high R-value which is the inverse of  
cob's ability. "A good conductor of heat (cob) is a poor resistor of  
heat." We need to educate ourselves and the building officials on  
building with thermal mass. I've been reading a lot on passive solar  
design. There's no need to "do" any more tests because they've  
already been done and books written. I've read a lot about earth- 
sheltered construction and they use passive solar design with high  
thermal mass walls. Although they're usually concrete the same  
principles apply to cob design. The U-value of 12" of poured concrete  
is 0.55 but cob is probably more similar to brick, which 12"  is  
0.31. if codes allow a concrete walled house, they should allow cob.  
By the way, 12" of poured concrete has an R-value of 1.8 if you do  
the math from the U-value. 12" brick is 3.23.
Damon in GA, USA

On Jul 21, 2011, at 5:57 PM, David Thurman wrote:

	"The current  base model for insulation in codes is based on the BTU  
drop from interior to exterior through a thermal envelop with no  
occupant. It's a math model and it has no basis in reality except in  
math. Thermal mass is a much more efficient model but that is based  
on how it "Feels" rather than on math." - David Thurman