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Despite the fact that the air temperature gets down as low as 12° F during the winter, and above 100° F during the summer here in the mountains of Arizona, the soil temperature 10-feet below the surface remains at a near constant 55-65° F all year.

When air is slowly drawn using a small fan through plastic pipes buried at this depth, it will be PRE-cooled during summer and PRE-heated during winter, providing natural climate control with much less energy than conventional heating and cooling.

Earth Tubes are reported not to work well in where humidity averages 90% or more, so they should work well here in the high desert mountains of Arizona.

A 220-foot long tube of 8″ diameter SDR-35 PVC pipe is assembled above a 10-foot deep trench. http://www.dpcpipe.com/sdr35.htm http://www.dpcpipe.com/airduct.htm
This trench in the picture was dug using a Takeuchi TB135 Excavator supplied by Hertz Equipment Rental.

In order to avoid the dangerous work of entering this deep trench, the tube is lowered slowly using ropes attached to metal fence posts every 4-feet along the complete length of the tubes.

A total of three 220-foot long tubes were lowered within the 10-foot deep trench, providing a total length of 660-feetof earth tubes to be studied at the center.