How does it work?
Imagine living in an underground home. You’re completely buried, just underneath the frost line. Inside the earth, the temperature is a cool and constant 55°F. One small heater is all it takes to raise your temperature to a comfortable 75° – year round, any season. Your heating and cooling bills would be almost nothing! But building such a house is problematic — there are issues with excavating, reinforcing, water seepage — in short, a nice idea but not always practical.