Homes built to maximize sustainability often double as landmarks. It can be awe-inspiring to look at the architecture that lends itself well to the landscape around it, or it can be useful to see how someone balanced conflicting sustainable practices, such as rooftop gardens, rainwater collection, or solar panels.

However, these types of homes are typically difficult to find, difficult to explore, plus challenging to build. Earthships are an exception to these difficulties while still maintaining a sustainable focus. Earthships make it easy to get involved, both for people looking to build their own as well as for sustainable architecture fanatics.

What makes Earthships so sustainable is that they are all built around interconnected design principles.

First, architect Michael Reynolds designed Earthships to be built out of local and recycled materials. Being constructed from local materials means less energy is used in transporting materials. It also means designers have to pay attention to the local environment: what materials would harm the ecosystem if used, how to adjust for less rain, colder winters, less sun, and what natural disasters are more likely to occur.

These homes can be designed to withstand hurricanes and be up to 40% fire resistant. Of the recycled materials, the most important is old tires. Old tires are hard to dispose of because they degrade slowly and give off toxic chemicals when burned. The world produces over 1.5 billion tires a year, leaving the old tires without a safe place to be stored. Earthships use these tires as cheap building materials filled with local dirt and covered in mud plaster.

Stability and thermal mass are two bonuses for using old tires. Each layer of tires is placed one and a half inches more to the outside than the lower layer. Instead of the weight of the roof being directly on the walls, the slant puts more of the load on the dirt behind the walls.

On the inside, plaster can be built up, so the walls are vertical. Also, the rubber tires provide more spring for the walls, lessening the damage of earthquakes.

Tires also give the walls high thermal mass, which is the ability of a material to store heat. Along with insulation—the ability of a material to reduce the heat transfer rate—this maintains a comfortable temperature inside the house.

Earthships use windows, walls, and vents to heat and cool the house without any use of electricity. This model is known as passive solar heating.

In the winter, windows facing the equator let in the maximum amount of sunlight to heat the home like a greenhouse. The walls store the heat and release it slowly at night, keeping the house ~70°F.

In the summer, the roof overhangs the windows preventing the sun from shining directly inside. The already captured warm air rises up and out of the house through vents in or near the roof. The vacuum then pulls in 55-60°F air through cooling tubes that are ~30’ long and pull outside air underground. There, the natural temperature of the earth conditions it before it goes inside.

Earthships do still use electricity for refrigerators, outlets, etc., but this is all generated sustainably; solar and wind electricity is the third design principle.

Solar power is typically responsible for the majority of output, but in cloudier climates wind power generation can complement solar power generation. The design includes efficient lighting and appliances, therefore, reducing electricity costs and maintaining all modern conveniences.

Earthships make the most of rainy days when they cannot collect solar energy via rainwater harvesting,  meaning all water is collected from rainfall and precipitation, even in desert climates.

The water passes through two filters with holes ranging from three hundred to twenty-five μm. After this, the water can be used for showering or laundry. Some Earthships stop there, but if you wish to drink the water, you may boil it or put it through a water purifier. Others possess a twelve μm hole filter and a UV or ceramic silver purifier for their drinking water built within. Any water the house collects is first used for things like hand-washing or cooking.

Next, the gray, or wastewater, goes to indoor gardens. These gardens use phytoremediation to filter the water as part of the fifth and sixth design principles: contained sewage treatment and food production.

The plant beds are on an incline, so the water flows through the dirt and root systems of the plant. Once it reaches the bottom, a solar-powered pump will take it back to the top.

Many of the plants grown in Earthships are edible, allowing the tenants sustainable produce. From the indoor gardens, the purified water is used to flush toilets. Now considered black water, the water is then pumped to outdoor landscaping where it waters fruit trees and other plants. This is the fourth time it is used, evaporating into the atmosphere afterward.

As you can see, Earthships are incredibly efficient and go beyond other green homes. Anyone interested in exploring for themselves may use MapHub to discover locations of Earthships, visitor centers, and even Earthship hotels. There is now no reason you can’t experience living in an ultra-sustainable house.

For those looking to build an Earthship or wanting to know more the construction aspect, there are several options such as the Earthship Academy, an internship, opportunities to travel and develop Earthships, and non-profits taking volunteers such as Veterans Off-Grid.