Although, this technique is essentially used for cooling the air in Hot and dry climates, it can also be used for winter heating. Earth- air tunnels may be considered as special types of wind towers connected to an underground tunnel. The cooling process is based on the fact that the temperature a few meters below the ground is almost constant throughout the year. A wind tower is connected to the underground tunnel, which runs from the bottom of the wind tower to the basement of the building. The wind tower catches the wind which is forced down the tower into the tunnel. The temperature of the tunnel, being lower than that of the ambient temperature, cools the air before it is circulated into the living space. In winter, the temperature of the air tunnel is higher than the ambient temperature and hence warms the air passing through it.
Sensible cooling can b aided by evaporative cooling. To reduce the underground temperature, the ground can be shaded using vegetation and can be wetted by sprinkling water. This water seeps through and dampens the tunnel walls. Consequently, air from the tunnel is evaporatively cooled as it passes through the tunnel. Another variation possible is to use buried pipes instead in place of tunnel.