Cob: Thermal Mass and R-values

[Kelly, Sean]

Howdy Cobbers!

  Considering all the messages on cob, insulation r-values and all that
junk, here a is pretty good article on R-values and Thermal Mass from
Environmental Building News...

http://www.ebuild.com/Archives/Features/Thermal_Mass/Thermal_Mass.html

Thanks everyone for all the perlite/vermiculite info... any way anyone knows
of to determine how much insulating capacity a given amount of perlite (if
vermiculite absorbs water, that is no good...) may add to a cob mix?  I see
some conductivity ratings for a perlite/gypsum plaster on the schundler
site, is this the same as an R-value or do you have to calculate an R-value
from that?  I am thinking of using a perlite enhanced cob for an extra foot
or so of thickness on the outside of the wall (as I have said before), and
would wonder how much r value I could get from that.  Would have to do some
testing of that mix and see where it loses it's strength... maybe using a
finer grain of perlite would help too, I mean sand doesn't weaken cob, maybe
micronic perlite wouldn't either.  Well, enough for now.

Sean