It may not be cheaper but it is much easier on the resource base. Straw is a virtual throwaway item in many places, though I read that rice farmers in N. Cal are making ethanol out of it. And the R-factor is awesome. Some framing required, modified timber framing maybe, and steel could be used to good advantage.

T, you surely know the answer to my question (I should know it): how thick would a framed wall with fiberglass insulation need to be to have R-factor of R-28?

__________________
Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K