The BLUE represents the buffer zones.  These areas are subject to wider temperature swings so are not considered as “living areas”.  Entrances into the building should always subject the buffer area to the extremes of the outdoors rather than the living area.

The RED area represents the comfortable living area - analogous to the inside chamber of a thermos.  It is better to expose the living area to the relatively mild temperature swings of the buffer zone than directly to an exterior wall.  

The earth connection preheats the buffer zone to approximately 55 degrees F in the dead of winter.