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Earthships are earth-sheltered autonomous buildings made of tires rammed with earth, which are usually arranged in a "U" or horseshoe shape. Each tyre is rammed full of earth using a sledge. Depending on its size and the soil density a tyre may weigh more than 300 pounds when properly prepared. Windows on the sunny side admit light and heat. The "U" shape of the structure faces South in the northern hemisphere, and North in the southern hemisphere, so that the house will catch maximum sunlight in the colder months.

Internal, non load bearing walls, are often made of a "honey comb" of recycled cans separated by concrete. The walls are then usually thickly plastered, using the pull-tabs on the cans as a lathe to hold the adobe and stucco.

==Potential Advantages==
* Having an earth-bermed home with windows facing south is a good idea in any northern hemisphere climate requiring heating.
* Collecting rainwater that falls on the roof reduces the runoff impact of the building and may reduce water and even sewer service fees.
* Having a combination of photovoltaic cells and wind generation is a prudent way to provide electricity in many situations.
* Using curved modules as horizontal arches to resist earth loads is a sound structural design.
* On site processing of process water, grey water and black water using plant beds may reduce the environmental impact of the building.
* Rubber tires make a wind and puncture resistant wall.  They may be safe from outgassing when plastered semi airtight.
* Rubber tires are usually free and it may be possible to be paid to take them.

==Potential Disadvantages==
* The sloped glazing may be hard to keep water tight and allow excessive solar gain in summer. New designs call for vertical windows with an overhang.
* Un-insulated ground coupled thermal mass presents a large potential for heat loss especially in climates with a heating season.  This varies to a degree with soil type and moisture content.
* Rubber tire walls tend to lack structural stiffness and may require perpendicular stiffening ribs. 
* Many problems exist in early earthships and designs in the first books. In every book further down the series, problems from previous books are fixed.
* Novel design may diminish resale value or make buyers more difficult to find.
* Intimate ground contact of this approach many increase hazards due to Radon , other soil gasses and water intrusion.
* Packing or ramming dirt into the inside of a tire appears to be a very labor intensive process.
* Many Earthship builders are drawn to this system by its apparently low environmental impact.  However, if this, or any building system, is not highly thermally efficient it seems unreasonable to consider it green.
* Earthship designs, like other home designs, may require a substantial thermal analysis and redesign to adapt to different climates.

== Resources ==
* [http://www.earthshelteredtech.com earth sheltered technology, inc.]