Earth Tube Ventilation: Passive Heating and Cooling for Energy-Efficient Homes The image illustrates an earth tube (also known as an earth–air heat exchanger) system, a passive design strategy that uses the stable temperature of the ground to heat and cool a home naturally throughout the year. This approach significantly reduces the need for conventional air conditioning and heating systems. How Earth Tubes Work Just a few meters below the surface, the ground maintains a relatively constant temp