An Earthship is a type of passive solar house that is made of both natural and recycled materials (such as earth-filled tires. They are intended to be "off-the-grid ready" homes, with minimal reliance on both public utilities and fossil fuels.
The Earthship as it exists today began to take shape in the 1970s. Michael Reynolds wanted to create a home that would do three things: first, it would utilize sustainable architecture and material indigenous to the local area or recycled materials wherever possible; second, the homes would rely on natural energy sources and be independent from the "grid"; finally, it would be feasible for a person with no specialized construction skills to build.
There are a couple of design features that are unique to Earthships. First, the geography of the land plays an important role in successfully building this type home. Building into a earthen berm is best but soil can be built up to create a earthen wall (trombe wall). The second feature is attention to the shape in order to gain passive solar efficiency. The outer walls in the majority of Earthships are made of earth-rammed tires, but any dense material with a potential to store heat, such as concrete, adobe, earth bags, or stone, could theoretically be used to create a building similar to an Earthship. The tire walls are strengthened by using concrete in the tires on the ends, called "concrete half blocks".
Earthship homes tend to be more expensive to build and a little more sophisticated pertaining to greywater, solar energy collection and rainwater harvesting efforts. The needed terrain to keep costs of acquiring soil may prove to be more difficult to locate.