Earthship

An Earthship is a type of home that takes care of its own needs with regard to energy, water, waste disposal and sometimes even food production. It achieves a high level of energy efficiency by using the sun's heat as much as possible and having heavy insulation. The idea is to have a home with no pipes or cables coming in or out: no electrical lines, sewage pipes, water mains

Earthships are intended to be built by people who are not trained builders.

Earthships are built of earth rammed into old tin cans or tires. This means the majority of building material is earth found on-site and the rest of it is recycled. These materials are cheap or free and can be used with very little energy-use or environmental impact.

Earthships are the brainchild of Mike Reynolds and are designed and marketed by Earthship Biotecture of Taos, New Mexico.

Structure

Rammed earth tires

Earthships are usually made of recycled rubber tyres with earth packed into them. However, any dense material with a potential for thermal mass, such as concrete, adobe, or stone could be used. Rammed-earth tyres have the following advantages -

1. Unlike such materials as concrete, they can be used by anyone. No special equipment is required to make them or use them. 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, 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). The method by which scrap tires are converted into usable "bricks" is simple and affordable: earth is packed in using a sledgehammer.
2. They have great load-bearing capacity.
3. 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.

The rammed earth 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. This is a very labour-intensive process. 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.

A fully rammed tire is about 2 feet 8 inches wide. This is big enough to surpass conventional requirements for structural load distribution to the earth.

Internal walls

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.

Structural shape

Earthships are based around one or several U-shaped modules. Each of these has a wall of rammed-earth tires several feet thick and a floor that is below ground level. Being partially submerged like this allows the house to take advantage of the thermal storage properties of the earth.

Roof

The roof of an Earthship is heavily insulated – often with earth or adobe – for added energy efficiency.

Water

Rainwater harvesting

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, and described as "Greywater".

Greywater

Greywater is water that has been used and is unsuitable for drinking, but can still be used for things like cleaning. Before the greywater is reused in an Earthsip, 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, ...). Water 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 and used to flush 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 (5,08 cm) 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 flush 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) are stored is in a small room referred to as the "systems package".

Electricity

Earthships are designed to collect and store their own energy from a variety of sources. The majority of electrical energy is harvested from the sun and wind. Photovoltaic panels and windturbines located on or near the Earthship generate DC energy that is then stored in several types of deep-cycle batteries. The space in which the batteries are kept is usually a special, purpose-built room placed on the roof. Additional energy, if required, can be obtained from gasoline-powered generators or by integrating with the city grid.

In an Earthship, a Power Organizing Module is used to take stored energy from batteries and inverter it for AC use. The Power Organizing Module is a prefabricated system provided by Earthship Biotecture that is simply attached to a wall on the interior of the Earthship and wired in a conventional manner. It includes the necessary equipment such as circuit breakers and Voltage converter. The energy run through the Power Organizing Module can be used to run any household appliance including washing machines, computers, kitchen appliances, print machines, vacuums, etc. Generally, none of the electrical energy in an Earthship is used for heating or cooling.

Climate

The Earthship aims to maintain a comfortable temperature passively i.e. without reliance on systems that require energy. It does this by maximizing the effect of thermal mass and solar heating and by using building materials that are heavily insulated.

Windows on sun-facing walls admit light and heat. 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.

Mainly, the Earthship tries to take advantage of the properties of thermal mass and passive solar heating and cooling. Examples are large front windows with integrated shades, trombe walls and other technologies such as skylights or solar trackers (which also generate electricity).

The load-bearing walls of an Earthship provide a dense thermal mass that will soak up heat during the day and radiate heat during the night, keeping the interior climate relatively comfortable all day.

In addition to high thermal mass, some Earthships may be earth-sheltered. The benefits of earth-sheltering are twofold because it adds to the thermal mass and, if the Earthship is buried deep enough, allows the structure to take advantage of the Earth's stable temperature.

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).

Natural ventilation

The earthships usually use their own natural ventilation system. It consists of cold(er) air coming in from a front ("hopper") window, especially made for this purpose and flowing out through (one of) the skylights that are placed on the earthship. As hot air rises, the system maintains itself and keeps sucking in (and out), air.

Heating problems

Bottle walls are used in earthships such as this earthship bathroom, located in the Phoenix Earthship, Taos, NM, USA. Earthships rely on a balance between the solar heat gain and the ability of the tire walls and subsoil to transport and store heat. The design intends to require little if any auxiliary heat. Some earthships have suffered from overheating and some from over-cooling.

Some earthships appear to have serious problems with heat loss. In these cases heat appears to be leaking into the ground constantly during the heating season and being lost. This situation may have arisen from the mistaken belief that ground-coupled structures (building in thermal contact with the ground) do not require insulation. The situation may also be due to large climatic differences between the sunny, arid, and warm Southwest (of the USA) where earthships were first built and the cloudier, cooler, and wetter climates where some are now being built. Malcolm Wells, an architect and authority on earth-sheltered design, recommends R-value 10 insulation between deep soils and heated spaces. Wells's insulation recommendations increase as the depth of the soil decreases.

In very limited and specific situations, uncommon during the heating season, thermal mass can marginally increase the apparent R-value of a building assembly such as a wall. Generally speaking, thermal mass and R-value are distinct thermodynamic properties and should not be equated. Thermal performance problems apparently seen in some earthship designs may have occurred because of thermal mass being erroneously equated to R-value. The R-value of soil is about 1 per foot.

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 different 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.
• 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.

Building guide download

A building guide is available on The Pirate Bay:

• Vol. 1, on architectural features
• Vol. 2 and the water, energy and other systems
• Vol. 3, on the broader implications of this sort of living

History

The history of the earthship was featured in the 2007 documentary "Garbage Warrior":

The Earthship began to take shape in the 1970s. Designs were at first very experimental, but have been improved over time.

Currently, Earthships are in use in almost every state in the United States, as well as many countries in Europe. In 2000 Mike Reynolds and Daren Howarth launched Earthship Biotecture Europe to explore and evolve the concept of the Earthship in Europe. Two more directors were appointed to Earthship Biotecture Europe in July 2006 – Kevan Trott and Kirsten Jacobsen.

Earthship Biotecture has now finalized plans to build 16 Earthship homes in Brighton.

Further reading

• Schirber, Michael. "Making Earthships Mainstream" on Going Green at msnbc.com, November 12, 2007.
• Earthship Florida Project

References - other

• Hewitt, M. and Telfer, K. (2007). Earthships: building a zero carbon future for homes. ISBN 9781860819728
• Klippel, James H. http://www.garrellassociates.com/EcoDesign.html, green page
• Reynolds, Mike. (2000). Comfort In Any Climate, Taos: Solar Survival P. ISBN 0962676748