Cob: Insulation etc

[Sojourner]

Mike Holland wrote:
> 
> Thought I'd add my two francs' worth to the insulation question...  We are
> renovating a 17th-18th century cob (bauge) building in the centre of France
> (photos etc still visible at http://perso.wanadoo.fr/mica ).  The walls are
> 12 - 18 inches thick, no windows on the north wall, relatively small
> non-insulated windows on the south facing side.  We heated through the cold
> season on an open log fire and consumed about 10 cubic metres of wood in 1m
> logs, plus a couple of 13kg bottles of LPG, at a total cost of around
> 2500-3000 francs.  It was well livable but on the coldest nights (less
> than -12 C) we were glad of our thick duvet...  We've therefore done some
> research on local solutions for insulation and we're going for a hybrid
> solution.  Firstly in the new bathroom area, we'll use plasterboard backed
> with 20cm of Rockwool (mineral wool - slightly less hazardous than glass
> fibre for handling, but you still want to wear mask & disposable overalls,
> and vacuum well afterwards to remove the fibres/dust).  We're using this
> primarily because we want it done quickly and these materials are standard -
> and local tradesman know how to install them.

Hey, now here's another similar idea - what if you embedded wood in the
inner wall of your cob and used that to tack up interior siding?  This
is assuming you wouldn't miss the look and feel of the cob wall on the
inside of the house.  If you would, then don't bother to read any
further because this wouldn't work for you.

The interior "siding" could be anything from gypsum board to rough sawn
lumber.  Thick paneling would even do it (but not the flimsy stuff
that's usually sold to be put up over gypsum board).  You could even use
exterior grade T1-11.

Would the wood embedded in the walls have to be PT?  Or would normal
untreated wood be ok, since the walls will not actually be wet (better
not be!)  This would act like vertical "lathe", like they used to use
for plastering.

Then you could drop insulation down behind the walls, anything from
blown in cellulose to sawdust or any other substance.

Would you have to take special steps to make certain that the cob mix
would hold with the weight of the "lathe" and the siding?

That right there might scotch the whole idea, if the cob couldn't hold
up to this.

Holly ;-D