Earth-Sheltered Housing
From ZombieSquadWiki
Earth-Sheltered homes are created by burying or berming all or part of a house with earth.
The addition of earth in this way adds a large thermal mass that is typically around the same temperature as the ground temperature. Large thermal mass makes the structure more energy efficient as its internal temperature will tend towards the temperature of the earth, as opposed to ambient air temperature. Berming and burying also adds ballistic resistance, radiation resistance, and fire resistance.
