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Earthships: The Greenest Off-Grid Homes

written by: KennethSleight•edited by: Paul Arnold•updated: 10/20/2011

While they may look like something out of a sci-fi movie, Earthships actually exist in every state of the Union and in several nations in Europe. These self-sustaining homes are among the most eco-friendly structures on Earth due to the materials they are made of and the power sources they use.

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    Earthship homes were developed in Taos, NM in the early 1970s by American architect Michael Reynolds. He had a radical vision of creating a fully sustainable home from recycled materials and items reclaimed from garbage. After years of building Earthships and sustainable buildings all over the world he established the Earthship Biotecture Company which offers guidance, advice and building plans for those interested in constructing their own Earthship home.

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    Brighton House

    Brighton House 
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    Foundation and Design

    Rammed Earth Tire An Earthship home is typically made from earth-rammed tires. These are used to construct the exterior walls of the entire structure except for the south-facing wall (in the Northern Hemisphere). The south wall is primarily large glass panels that are used for passive solar heating. A single earth-rammed tire can weigh upwards of 300 lbs., and therefore it is more efficient to construct them on site than to have to move them.

    The process for creating the foundation wall is extremely labor intensive and requires at least two individuals. The first person digs the dirt, shoveling it into the empty tire, and the second individual pounds the dirt into the sides of the tire (this is the ramming). The tire is turned throughout the fill process to ensure that the fill is loaded evenly.

    In early versions of the Earthship these tires were simply covered with adobe or natural plastering. The insulation value was thus limited to the two and a half feet of dirt and the thin insulating rubber of the tire (an R value of about 5). This limited the placement of Earthships to areas that didn’t experience extremely cold temperatures. Today there are various insulation materials that are used directly over the exterior of the tire before the finish is applied. This has allowed Earthships to be built as far north as Ontario, Canada.

    Interior walls (and often casing walls for the tire structure) are created by stacking aluminum cans and mortaring them into place with cement. These walls are light and strong and can be designed in both straight lines and curves. Wire conduits can be built into the walls during construction to accommodate electrical needs and additional outlets can be inserted after construction with a simple wall punch. The thin layer of concrete and aluminum will open quickly and can be reinforced after the new wiring is installed.

    Standard Earthships are built with the signature “U" shaped design. In addition to the passive solar design of the southern wall most Earthships have active solar and wind collectors and use other sustainable methods including rain collectors and biological grey water filtration.

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    Ganges House

    Ganges House 
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    Energy Collection

    One of the main draws of these ultra eco-friendly homes is the ability to live off-grid. These structures don’t require a lot of energy to maintain their interior temperature and so the use of solar panels and wind powered generators is usually sufficient to cater for all their energy needs. Many of the Earthships have propane tanks for cooking and a backup hot water supply; these are the only utility bills.

    The solar units used to power Earthships are of the free-standing variety and provide most of the energy required to run the home. With the average monthly U.S. electricity bill coming in at around $104, a solar panel system that eliminates the need to be connected to the grid has the potential to save the Earthship owner over $1,200 dollars a year. If you are interested in knowing more about the energy savings from this type of application check out Solar Energy Potential.

    Wind turbines have initial costs ranging from $3,000 to about $10,000 but pay for themselves in under ten years. Here are some things to consider when choosing a home wind turbine.

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    Jacobsen House

    Jacobsen House 
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    Water Collection: Roof and Cistern

    A major off-grid living concern is the collection of water. Water capture is built into every Earthship design. Where most traditional homes have gutter systems to work moisture away the Earthship has raised ridges that keep water on the roof and direct it to the cistern.

    Roofs are south-facing and low sloped and contain channels that direct rainwater to a collection cistern. Above the cistern is a filtration system, usually gravel, to prevent debris from entering the water storage area. In areas that receive large amounts of snowfall the limited slope of the roof assures that the snow will melt and collect in the cistern instead of falling off the roof to the ground.

    On top of the water catchment system are a number of water saving and recycling systems, including one for greywater reclamation. This recycles water from sinks and showers to provide nutrients to plants and fill the toilet reservoirs.

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    Greywater and Solar Toilets

    The most important aspect of an Earthship home is its water usage. The Earthship design cuts daily water use by 75%, which is extremely important in the dry climates where they were developed. While the initial choice for toilets in an Earthship were those of the composting variety newer models include flush toilets and dry solar toilets. The flush toilet water (black water) is not reused within the structure but is instead pumped out to a solar enhanced septic tank where anaerobic decomposition occurs and the nutrients are used to grow plants.

    Greywater is the term used for water that has been used in the home and is not suitable for drinking. The greywater is routed through a grease filter and then through a living biological filtration system. This is series of planters where the plants act as natural filters to detoxify the water. This water is then used in a flush toilet system or to humidify the home (often used in a swamp cooler type system in very hot, dry areas).

    Because Earthships are built with recycled materials (tires and aluminum cans), earthen plasters, large wood beams, and glass panels they are more than carbon neutral, they are carbon negative releasing no excess carbon dioxide into the air. These are some of the most eco-friendly dwellings on the planet and are designed to be used for generations.

    The unique and stable design is both fire and earthquake resistant and the use of slow decomposing rubber means the walls of the main structure will remain intact for hundreds of years. For an in-depth look at the entire process of building an Earthship from the ground up check out Scott & Janis Derrick's Earthship voyage.