Cob R of dirt (was Cordwood Homes)

[bmyton at ccmail.uwsa.edu]

M J, 

You wrote:
>        From the book Earth Sheltered Housing Design (which was written using
>Minnesota's climate data) is a test where a heating-season comparison was
>made between two earth-sheltered roofs: the first had 9.8 feet of dirt over
>precast concrete, and the second had 18 inches of dirt over 3.9 inches of
>polystyrene on top of precast concrete. The almost-ten-feet of dirt yielded
>a 2.4% reduction of heat loss over the other one for the season. Not very
>much. It says "... in order to compete effectively with standard insulating
>materials, soil depths in excess of 2.75m (9 ft) would be required on the
>roof... the increased depth of the building would also reduce heat losses
>through the walls and floor."

Did 18 inches of dirt with polystyrene have much effect, then? Without knowing 
the numbers, it looks like you're saying that 9 feet of dirt on concrete was 
less effective than 18 inches of dirt over foam over concrete, where the foam 
would actually insulate the concrete from the dirt.

Am I interpreting correctly?

How are those jim-dandy earthships insulated, if auxiliary methods are used to 
supplement the earth sheltering?

Becky
in the Midwest, where more warmer is more better!