Cob Thermal properties of cob

[Shannon C. Dealy]

On Tue, 24 Feb 1998, Craig Hull wrote:

> On Sun, 22 Feb 1998, Shannon C. Dealy wrote:
> 
> >snip< 
> > The actual
> > values you will experience will depend heavily on the amount of straw in
> > the mix. 
> >snip<
> 
> Has this been verified? It would make sense but I would think it is also
> possible that the conductivity of the clay might so overwhelm the 
> insulative value of the straw as to make straw content nearly irrelevant.
> So far all I've seen is speculation. I would think a qualitative test of
> the therory that straw content (in reasonable amounts) affects insulative
> values would be much easier than a quantative test to measure R values
> would be.

You are correct, I have no information on experimental verification of
this, and since it has been a good 15 years since I last did any
mathematical modeling of thermal conduction, this is mostly an educated
guess based on anecdotal evidence, and I should have phrased it as
such. You caught me speaking off the top of my head again (where the hole
is located :-).  Since there is little information on the specifics of
R-value and cob mixes, I have started putting together materials to build
a small thermal test chamber, and hope to get some time in the next few
months to conduct some real tests.  Those of you who know me and the
lightning speed at which I accomplish things (like that thatching article
:-), should know by now not to hold your breath, and that the next few
months means sometime between now and the end of the millenium . . .  Wait
a minute, the end of the millenium is almost here, better make that the
end of the next millenium :-)

Shannon Dealy
dealy at deatech.com