[Cob] R value of cob vs strawbale (Deborah Denmark)

[Tys Sniffen]

I would agree with the suggestion of doing both.

To answer your basic question:  "does (3ft thick) cob have a good enough r-value for the north side of my house?" I would say no.

Cob has thermal mass, not insulate-ive qualities.  That massive wall, always in the shade, would never warm up in the winter.  It'd be pretty much like a cave wall - which is better than 20 degrees F, but not pleasant enough to have it as your house wall.  It would just always be sucking heat out of your room space.

Another whole tactic would be to do some sort of rocket/mass heater through that wall.  If I could do my cob house over again, I'd run a horizontal pipe through my north wall, have a firebox outside the house and the verticle part of my chimney on the other side of the house.  Similar to the traditional Asian house heater designs  - called Ondol - like this:

https://www.google.com/search?q=ondol&rlz=1C1CHWA_enUS606US607&espv=2&biw=1536&bih=758&source=lnms&tbm=isch&sa=X&ei=f1LaVO7aCsylNuGGhPgB&ved=0CAYQ_AUoAQ