Cob Thermal properties of cob

[Shannon C. Dealy]

On Fri, 20 Feb 1998, uwe wrote:

> Hi everybody,
> 
> this is my first post to the list, and I hope that I'm not asking a
> question which already has been asked "a thousand times". Does anybody
> know the insulation and thermal mass values of cob, compared to adobe
> and SCEBs (stabilized compressed earth blocks)? My feeling says that it
> should be the same, but I'm not sure.
> 
> Uwe

I have not seen much information about cob in this regard, though there
was a posting quite a while back:
 
   http://www.deatech.com/natural/coblist/coblist-web/0597.html

in which an R-value of 0.144 per inch was measured in an old cob building
in the UK, however there was no information provided (possibly none was
available) on the straw content of the cob mix.  Ultimately, because of
the high straw content of modern cob, you should expect it to have a
higher R-value and lower thermal mass than adobe and SCEB.  The actual
values you will experience will depend heavily on the amount of straw in
the mix.  I have heard estimates of values all the way up to around R-1.0
per inch, but in most cases, little or no information was provided on the
straw content (or estimated content) so it is difficult to give a specific
R-value.

If insulation is a concern to you, one experiment I was going to try in a
large dog house was to build a double wall cob structure that I could
pack full of straw to provide better insulation.

Shannon Dealy
dealy at deatech.com