Cob: Cob insulation value

[Charmaine]

Michael, the accepted estimate for cob is  R 1 per  4 inches thickness, 
 so 1/4 of an R per inch of density, give or take a bit.   Cob is MASS 
not insulation, this is why people keep discussing using a layer of 
light straw clay or woodchip-clay inside or outside as a thermal 
insulation for the cob.

If you have 10 deg weather at the worst  that seems pretty darn cold to 
me!  

Cob has been used in UK, Wales, etc. and all over the world, but 
remember people used what they HAD, it doesn' t mean it was the perfect 
material for the climate. The hearth was kept burning all winter to keep 
warm.  Heat continually moves OUT ...dissipating into the outdoors,  and 
firewood was plentiful then.

  I am sure if someone 500 years ago figured out that light straw clay  
1 to  2 ft thick was WARMER in winter they would have done it.    Cob as 
an external and internal plaster over some sort of better insulating 
wall material is an ideal mix of natural materials.

as a comparison I viewed a modern rammed earth wall house, the owned 
agreed that if he had it to do over again he would just have made a 
"walls" of any natural material- like woodchip  clay/straw clay.
 or Straw bales and then plastered with earth to get the  SAME 
beautiful  look with no where near the work.
 RE walls  done by owner builders are quite labor intensive and 
preventing voids and weak spots, requiring heavy forms, moving the 
forms,  loading the earth etc  it was a ton of work. ( no pun intended)


Ms. Charmaine  Taylor/ Taylor Publishing
http://www.dirtcheapbuilder.com    http://www.papercrete.com
PO Box 375, Cutten (Eureka) CA 95534
707-441-1632     tms at northcoast.com