Progress!

The wall materials have been delivered! The material shown for the exterior walls is essentially a white-painted sheet of steel on the exterior and interior surfaces, with 4 inches of styrofoam sandwiched in between, to provide both security and effective insulation from the maximum heat of early summer weather (often above 100 degrees Fahrenheit/40 degrees Celsius).   The choice of expanded styrene foam is due to it retaining its R-value over time due to not absorbing moisture and having a lower environmental footprint than comparable alternative materials.
building material delivery
Building material delivery on 16 September 2018
Photograph by Bill Elliot