Earthships = A New Way of Living

An Earthship is a type of passive solar home made of natural and recycled materials. Designed and marketed by Earthship Biotecture of Taos, New Mexico the homes are primarily constructed to work autonomously and are generally made of earth-filled tires, utilizing 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 the sunny side admit light and heat, and the buildings are often horseshoe-shaped to maximize natural light and solar-gain during winter months. Likewise, the thick, dense outer walls provide effective insulation against summer heat.

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 earth or adobe - for added 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, 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, or stone could theoretically be used to create an Earthship. However, the earth-rammed tire version of the Earthship is now the most common design, and is usually the only structure referred to as “Earthship”.

Unlike other materials, rammed-earth tires are more accessible to the average person. Scrap tires are ubiquitous 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. After testing the walls of an Earthship in Ridgway, Colorado, engineer Tom Griepentrog said, “It is my opinion that the construction method is equivalent to or better than the general quality, strength, effectiveness, fire resistance, durability and safety that is required by the uniform building code.”

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. In the year 2000, Mike Reynolds, in partnership with Daren Howarth, launched Earthship Biotecture Europe, an organization that aims to explore and evolve the concept of the Earthship within a European context. Two more directors were appointed to Earthship Biotecture Europe in July 2006 – Kevan Trott and Kirsten Jacobsen.

Systems

The Earthship was designed as a structure that would exist in harmony with its environment and be freed from the constraints of modern shelters which rely on centralized utilities. It is important that the Earthship create its own utilities as well as use readily available and sustainable materials. In order to be entirely self-sufficient the Earthship needs to be able to handle the three systems of Water, Electricity, and Climate. While these systems are not exclusive to Earthships, a properly designed Earthship must have these systems.

Collection

Earthships are designed to catch and use water from the local environment without bringing in water from a centralized source. Water used in an Earthship is harvested from rain, snow and condensation. As water collects on the roof it is channeled through a silt-catching device and into a cistern. The cisterns are positioned so they gravity-feed a WOM (water organization module), that filters out bacteria and contaminants, and makes it suitable for drinking. The WOM consists of filters and a DC-pump that are screwed into a panel. Water is then pushed into a conventional pressure tank to create common household water pressure. Water collected in this fashion is used for any household activity except flushing toilets the conventional way. Rather, the water used for flushing toilets has been used at least once already: frequently it is filtered waste-water from sinks and showers, as described under “Greywater”.

Greywater

Greywater, water that has been used and is unsuitable for drinking, is used within the Earthship for a multitude of purposes once it is reclaimed. First, before the greywater can be reused, it is channeled through a grease and particle filter/digester and into a 30”-60″ deep rubber-lined botanical cell, a miniature living machine, within the Earthship. This filter with imbedded plants can potentially also be used to produce food (by using a fruit tree, …). Oxygenation, filtration, transpiration, and bacteria-encounter all take place within the cell and help to cleanse the water (Reynolds 2000). Within the botanical cell, filtration is achieved by passing the water through a mixture of gravel and plant roots. Because of the nature of plants, oxygen is added to the water as it filters, while nitrogen is removed. Water taken up through the plants and transpired at their tops helps to humidify the air. In the cell, bacteria will naturally grow and help to cleanse the water.

Water from the low end of the botanical cell is then directed through a peat-moss filter and collected in a reservoir or well. This reclaimed water is then passed once more through a greywater board (see earthship.net) and used to flush conventional toilets.

Often, any greywater that is made at earthships is not polluted enough to justify treatment (its “pollution” being usually just soap, which is often not environmentally damaging). At earthships, the use of plants placed at outlets of fixtures is then practiced to regain the water and the nutrients lost (from the soaps, etc.).. Usually, a single plant is placed directly in front of the pipe, but mini drain-fields are also sometimes used. The pipe is made large enough (5,08cm) so that the formation of underground gas (from the greywater) is avoided. This is done with kitchen and bathroom sinks, and even showers, washing machines, and dishwashing machines. The plants are usually placed indoors with the sinks and outdoors with the washing/dishwashing machines and shower (to avoid indoor “floods”). Also, with the latter, larger drain-fields are used instead of a mere plant being placed before an outlet.

Black water

Black water, water that has been used in a toilet, was usually not created within many of the earliest earthships as the use of conventional toilets was discouraged. Instead, in the early days composting toilets were advocated, which use no water at all. However, with the new greywater treatment system design (used in Nautilus, Helios, …) created by Michael Reynolds, flush toilets have now found a place in the earthship and the general water system has been redesigned according to the new “6-step process”. Now, when the newly included flush-toilets are used, blackwater is not reused within the Earthship. Instead, blackwater is sent to a solar-enhanced septic tank with leach-field and planter cells (the whole being often referred to as the “incubator”). The solar-enhanced septic tank is a regular septic tank which is heated by the sun and glazed with an equator-facing window. The incubator stores the sun’s heat in its concrete mass, and is insulated, to help the anaerobic process. Water from the incubator is channeled out to an exterior leach field and then to landscaping “planter cells”

(spaces surrounded by concrete in which plants have been put). The cells are similar to the botanical cell used in greywater treatment and are usually placed just before and under the windows of the earthship.

In cases where it is not possible to use flush-toilets operating on water, dry solar toilets are now advocated, instead of regular composting toilets. If this is the case, obviously no black water is formed and the use of an incubator is thus (usually) not necessary. Instead, regular “planters” (plants used for sucking up water/nutrients) are then used. When using regular planters as well, no chemical soaps or detergents can be used.

The space where the WOM (water organization module), graywater pump panel, pressure tank, (first set of) batteries, and POM (power organising module) and stored is in a small room referred to as the “systems package”.

The Earthship is designed in such a way that the sun provides heating, ventilation, and lighting. To take advantage of the sun, an Earthship is positioned so that its principal wall, which is nonstructural and made mostly of glass sheets, faces directly towards the equator. This positioning allows for optimum solar exposure.

To allow the sun to heat the mass of the Earthship, the solar-orientated wall is angled so that it is perpendicular to light from the winter sun. This allows for maximum exposure in the winter, when heat is wanted, and lesser exposure in the summer, when heat is to be avoided. Some Earthships, especially those built in colder climates, use insulated shading on the solar-orientated wall to reduce heat loss during the night (Reynolds 2000).

Potential advantages

• Having an earth-bermed home with windows facing the sun is a good idea in any climate where heating is required.
• 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 runoff water, grey water, and black water using plant beds reduces 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. It also is beneficial to keep them out of landfills or prevent them from being illegally burnt.
• Potential to eliminate utility bills.
• The structure is highly moldable to your own aesthetic tastes.

Potential disadvantages

• The sloped glazing may be hard to keep watertight and in warm climates allows excessive solar gain in summer. In colder climates, the glazing itself, which has far poorer insulating properties than any other component, will obviously be the major conduit of heat loss in winter. New designs call for vertical windows with an overhang.
• Uninsulated 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.
• Most solar photovoltaic systems suffer from poor efficiency and some wind systems only generate in periods of high wind velocity.
• The novel design may diminish resale value or make buyers more difficult to find.
• The intimate ground contact inherent in this approach may increase hazards due to soil gases including Radon, and those due to water intrusion.
• Packing or ramming dirt into the inside of tires is a very labor-intensive process.
• Many Earthship builders are drawn to this system by its apparently low environmental impact. However, this is only valid if the design is highly thermally efficient. Earthship designs may require substantial thermal analysis and redesign to be adapted to non-Southwest USA climate.
• Earthships built with concrete, sand bags, or adobe and with better solar and heat control perform better.
• Earthships are usually built in areas of extremely low population density, so unless they are entirely self-sufficient, a significant amount of fossil fuels could have to be expended in their construction because of the transportation of materials and workers. They can be built anywhere, however, and this can mitigate certain issues dealing with fossil fuels and transportation.