“Above-ground” houses have some of their external walls exposed to winter winds that get very little sun to warm them. With cold rain driving against these walls the effect is made worse, draining heat from the structure. Although the north facing windows will be receiving the sun’s warmth, the southern walls are actually trying to take it away. Winter winds cool the structure down and the occupants rely on insulation to keep heat in the house. Any form of heating, either free from the sun or by an internal heat source is always trying to make up the loss to the rear walls.

By building into the ground, the temperature within an Earth Sheltered House remains relatively stable. The more the earth contact, the more the stability. We can assume that the ground temperature at the depth we are building at will be equal to the average yearly air temperature of the site. In Adelaide it’s around 17 degrees. So the walls that are in earth-contact will probably never get much below this.
However the need for light and ventilation to all the rooms means there will be some parts of the house exposed. Although this exposure results in some overall ”thermal bleeding” it also allow us to catch winter sun through the north facing windows. Any required heating will only have to heat the air within the 'shelter space', not the building structure.

In real-life terms, this means that air-conditioning is not needed, and heating would usually only be needed on days when there was no direct sun.

This means considerable financial and environmental savings.