An earthship is a type of passive solar house made of natural and recycled materials. Designed and marketed by Earthship Biotecture of Taos, New Mexico, the homes are primarily constructed to work as autonomous buildings and are generally made of earth-filled tires, using thermal mass construction to naturally regulate indoor temperature. They also usually have their own special natural ventilation system. Earthships are generally off-the-grid homes, minimizing their reliance on public utilities and fossil fuels. Earthships are built to utilize the available local resources, especially energy from the sun. For example, windows on sun-facing walls admit lighting and heating, and the buildings are often horseshoe-shaped to maximize natural light and solar-gain during winter months. The thick, dense inner walls provide thermal mass that naturally regulates the interior temperature during both cold and hot outside temperatures.
Internal, non-load-bearing walls are often made of a honeycomb of recycled cans joined by concrete and are referred to as tin can walls. These walls are usually thickly plastered with stucco.
The roof of an Earthship is heavily insulated – often with two layers of four inch poly-iso insulation – for energy efficiency.
The Earthship as it exists today, began to take shape in the 1970s. Mike Reynolds, founder of Earthship Biotecture, a company that specializes in designing and building Earthships, wanted to create a home that would do three things; first, it would be sustainable architecture, using material indigenous to the entire planet as well as recycled materials wherever possible. Second, the homes would rely on natural energy sources and be independent from the “grid”, therefore being less susceptible to natural disasters and free from the electrical and water lines that Reynolds considered unsightly and wasteful. Finally, it would be economically feasible for the average person with no specialized construction skills to be able to create.
Eventually, Reynolds’ vision took the form of the common U-shaped earth-filled tire homes seen today. As a concept, the Earthship was not limited to tires – any dense material with a potential for thermal mass, such as concrete, adobe, dirtbags, or stone could theoretically be used to create a building similar to an Earthship. However, the earth-rammed tire is part of the definition of an Earthship.
Unlike other materials, rammed-earth tires are more accessible to the average person. Scrap tires are plentiful around the world and easy to come by; there are an estimated 2 billion tires throughout the United States. As of 1996, as many as 253 million scrap tires were being generated each year in the United States, with 70% being reclaimed by the scrap tire market (leaving perhaps 75 million scrap tires available for reuse as whole tires). In addition to the availability of scrap tires, the method by which they are converted into usable “bricks”, the ramming of the earth, is simple and affordable.
The earth-rammed tires of an Earthship are usually assembled by teams of two people working together as part of a larger construction team. One member of the two person team shovels dirt, which usually comes from the building site, placing it into the tire one scoop at a time. The second member, who stands on the tire, uses a sledge hammer to pack the dirt in. The second person moves in a circle around the tire to keep the dirt even and avoid warping the tire. These rammed earth tires in an Earthship are made in place because, when properly made, they weigh as much as 300 pounds and can be very difficult to relocate.
Additional benefits of the rammed earth tire are its great load-bearing capacity and its resistance to fire.
A fully rammed tire, which is about 2 feet 8 inches wide, is massive enough to surpass conventional requirements for structural load distribution to the earth. Because the tire is full of soil, it does not burn when exposed to fire. In 1996 after a fire swept through many conventional homes in New Mexico, an Earthship discovered in the aftermath was relatively unharmed. Only the south-facing wall and the roof had burned away, compared to the total destruction of the conventional homes.
Currently, Earthships are in use in almost every state in the United States, as well as many countries in Europe. The use of insulation on the outside of tire walls, which was not common in early designs, is improving the viability of Earthships in every climate without compromising their durability. Earthships are continually being built by Earthship Biotecture around the world. Their popularity and use of inexpensive materials has inspired many to build their own homes as well.