Energy Efficiency

Grade Level: 3-10

Source: Schlumberger Excellence in Educational Development. Adapted with permission.


In Swords into Plowshares: At Home in a Missile Silo, Tony Crossley says of his underground home: “The winters are bitterly cold, the summers feature spectacular afternoon thunderstorms and occasional tornadoes, and throughout the year we get days when the wind is very strong. Underground it’s always quiet and peaceful, and no matter how cold it gets outside, the interior never freezes, even though we don’t have any heating yet.”

Even in an area with an extreme climate, the ground maintains a relatively constant temperature. Because of this, a house that is built partly or entirely underground can be more energy-efficient than a home above ground. During the winter, the ground is warmer than the air. During the summer, it is cooler.

Any large mass of earth tends to maintain a constant temperature. You can see for yourself how this works by testing how long it takes for a thermometer buried in sand or soil to reach the temperature of surrounding air.



  1. Record the room temperature as shown on the thermometer.

  2. Put the thermometer in the refrigerator or freezer to find the air temperature inside. Check the temperature at one-minute intervals until it does not change from one reading to the next. Record this low reading.

  3. Take the thermometer out of the refrigerator or freezer and allow it to return to room temperature.

  4. Carefully stick the thermometer into the cup of sand or soil and record the temperature on the first line of the chart opposite the word “start.”

  5. Put the cup into the refrigerator or freezer.

  6. Check the temperature every 10 minutes and record your results on the chart. Continue to do this until it reaches the temperature that you recorded in Step 2 above. It may take more or less than 120 minutes for the temperature of the sand or soil to reach the temperature of the surrounding air!

Temperature Change

Time in minutes