Earthship

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Earthships are earth-sheltered autonomous buildings made of tires rammed with earth, which are usually arranged in a "U" or horseshoe shape. Each tyre is rammed full of earth using a sledge. Depending on its size and the soil density a tyre may weigh more than 300 pounds when properly prepared. Windows on the sunny side admit light and heat. The "U" shape of the structure faces South in the northern hemisphere, and North in the southern hemisphere, so that the house will catch maximum sunlight in the colder months.

Internal, non load bearing walls, are often made of a "honey comb" of recycled cans separated by concrete. The walls are then usually thickly plastered, using the pull-tabs on the cans as a lathe to hold the adobe and stucco.

The roof of an Earthship is heavily insulated.

1 Heating Problems
2 Renewable Energy
3 Potential Advantages
4 Potential Disadvantages
5 See also
6 External links

[edit] Heating Problems

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 over-heating and some from over-cooling, due to a failure to adjust for local conditions.

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 due to 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 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. Well'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 due to thermal mass being erroneously equated to R-value.

According to KSU the R-value of soil is about 1 per foot.

[edit] Renewable Energy

Electricity may be obtained from renewable energy sources, such as solar cells, small windmills and microhydro turbines, removing the reliance on electricity from the power grid.

Earthships capture rainwater from the roof and store it in cisterns for use in the house, where "grey water" from the kitchen and shower is re-used in the window planters.

Earthships have survived forest fires, earthquakes, and windstorms. The oldest such structure known is over 30 years old, and continues to function.

The chief architect of Earthship Biotecture is Mike Reynolds. He has written five books on the subject, available from the Solar Survival Press.

In 2000, Mike Reynolds was forced to give up his architect’s license[1] due to a settlement in New Mexico. According to http://nmbea.org/.

"After several years of investigations stemming from homeowners' complaints to the Attorney General's Office, Reynolds last week surrendered his state contractor and architecture licenses as part of a settlement with the state Board of Architect Examiners and the Construction Industries Division."

3 large communities of Earthships exist in northern New Mexico (near Taos) and southern Colorado, USA.

[edit] Potential Advantages

Having an earth-bermed home with windows facing south is a good idea in any northern hemisphere climate requiring heating.
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 process water, grey water and black water using plant beds may reduce 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.

[edit] Potential Disadvantages

The sloped glazing may be hard to keep water tight and allow excessive solar gain in summer. New designs call for vertical windows with an overhang.
Un-insulated 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.
Many problems exist in early earthships and designs in the first books. In every book further down the series, problems from previous books are fixed.
Novel design may diminish resale value or make buyers more difficult to find.
Intimate ground contact of this approach many increase hazards due to Radon , other soil gasses and water intrusion.
Packing or ramming dirt into the inside of a tire appears to be a very labor intensive process.
Many Earthship builders are drawn to this system by its apparently low environmental impact. However, if this, or any building system, is not highly thermally efficient it seems unreasonable to consider it green.
Earthship designs, like other home designs, may require a substantial thermal analysis and redesign to adapt to different climates.

Homes built with concrete, sand bags, or adobe, following the concepts of above and adding better solar and heat control produce better performing earthships. Of course, many of these concepts are considered good concepts for architecture already.

In 2004, the very first Earthship in the UK was opened at Kinghorn Loch in Fife, built by volunteers of the SCI charity. And in 2005 the first earthship in England was established in Stanmer Park, Brighton.