Cob: RE: Insulation

[John Schinnerer]

Aloha,

-----Original Message-----
From: Kelly, Sean [mailto:SKelly at PinpointTech.com]
>Isn't this how double paned windows work?  I will admit I don't understand.
>Just wondering.

It is indeed.  The trick is that the space has to be small (narrow, that is)
enough that significant air currents don't start flowing - *moving* air
conducts heat/cold a lot faster than still air.  You'll notice that
double-pane windows typically have very little space between the panes, like
1/4" - 1/2".  Storm windows may have more and still be reasonably effective.
I believe when the gap gets to more than about 2" (for windows, anyhow) the
air movement between the panes starts to significantly degrade the
insulative value of having two panes.  I won't go into techweenie details
about convective air currents and all just now, but they happen... :-)

So...if one were to build a double-wall cob structure, one would want to put
something in the gap to keep air from flowing freely (straw, sawdust,
cellulose insulation, etc.).  This is what Rob Roy recommends in his
double-wall cordwood design, which is very similar to the proposed
double-wall cob design in terms of the basic idea.

John Schinnerer