There are many ways to heat and cool your house naturally, cheap/inexpensively, and easy, and earth tubes (I will call them "earthtubes" from now on) are one of the best ways I have used, ever, to accomplish this!
Most people work at a job to pay their expensive electric bill each month in order to alter the temperature in their homes, and others do their own labor directly such as cutting firewood for their wood stove during winter. Earthtubes are an excellent way to bring pre-warmed (tempered) air to fireplaces and woodstoves, so as to eliminate ice-cold drafts, which normally draw from around windows and doors to feed the fire.
However, earthtubes do an even better job of cooling your home in summer since they can, without any electricity whatsoever, bring the temperature inside the house down by 10 or even 20+ degrees, depending on the design of the home and how many earthtubes you have. If it is 99 degrees Fahrenheit outside, then it can be as cool as 79 degrees F inside. In my straw bale house I built in the 1990's in Nebraska, the inside temperature was closer to 70 degrees due to the R-50 insulation value in the walls from the bales.
How do they work, you might be wondering? They are basically 100-foot long PVC pipes with an entry and an exit that brings fresh air into the house. This works passively, so air rises out an open window in the house--this allows hot air out, and the vacuum effect draws cooler air in through the tubes. The tubes are buried far beneath the surface of the ground, so moisture from the air condenses out and exits the tube, leaving the dryer cooler air to enter the home. This process of convection and air exchange is what cools down the temperature inside each of the rooms.
Existing houses can be retrofitted to have earthtubes added on later, but most homes are built after the tubes are placed in the earth (much like plumbing is done) prior to construction. There are tricks and tips and full design instructions that I have in my book "Passive Solar Energy House Projects: A How-To Guide" (available here for $15).
I sold my straw bale house back in 1999 and the owners were already enthusiastic about the passive solar design (which is the best way to passively HEAT a house, besides to combine it with secondary choices: underground design, earth-sheltered construction, or a living roof... adding earthtubes for tempered air to feed a fuel-consuming heating apparatus/appliance/wood stove/fireplace is the tertiary choice for heating aids), but they were really SOLD on how well the earthtubes COOLED the house during the hot and humid mid-summer heat and have raved about it ever since!
Below are some links to my other blog pages for more information:
House Design Blunders: http://sunstarangel.blogspot.com/2012/07/house-design-blunders.html
Three Ways to Make a Fireplace More Efficient: http://sunstarangel.blogspot.com/2012/10/three-ways-to-make-fireplace-more.html
What is a Passive Solar House?: http://sunstarangel.blogspot.com/2012/07/what-is-passive-solar-house.html
Learn more, GET MY BOOK with complete instructions on constructing earthtubes and other solar home projects! (including solar/wind power, build a solar water distiller, make a solar oven, build a tornado and hurricane resistant house, and passive solar home design): www.createspace.com/1105919
Please LIKE our solar book Facebook page!: https://www.facebook.com/PassiveSolarEnergyHouseProjects