Provide a roof over our heads, as they say, and let you have your own four walls. All this assembled on your piece of ground, and what you got is a pretty standard home. Nothing special, that's in fact what most houses offer. But could there be more?
Earthships were developed by architect Michael Reynolds in Taos, NM, with the goal of creating fully autonomous off-grid houses that take care of their residents’ basic needs. These needs include everything a building can provide, which is quite a lot, actually: It starts with basic shelter from the rain, wind, and temperatures that are outside our range of comfort. Most conventional buildings can’t even keep up with these simple demands, since they are so affected by outside temperatures that they need an active heating or cooling agent inside. But Earthships offer more than just passive heating and cooling: They harvest water, they generate electricity, they grow food, and they even treat all their waste water right on site. Apart from that, Earthships are built from recycled and natural materials.
There are many types of sustainable houses out there, from straw-bale to superadobe, each with their benefits and shortcomings. Eartships are no exception. However, they do cover a lot of needs, all in all, so I want to mention them first.
For many people who have seen an Earthship, the first and most obvious thing that comes to mind are the big slanted windows forming the southern side, and the other three walls made out of compacted tires. And true enough, these two features include some of the most practical benefits of these passively cooled and heated houses, especially in the high desert climate they’ve been developed in.
Passive solar means you want use the sun's energy directly for heating the house. That's where big windows come in. To maximize solar gain, they are set up slanted, at the angle of the building's latitude. This way the winter sun, shining from its lowest angle, will reach all the way to where the floor meets the northern wall.
As for the tires, they are not really essential. In fact, in a number of countries, where the recycling or upcycling, or in fact any use of discarded tires is against the law, Earthships are built using other techniques, such as earthbags, for example. So ultimately tires are not a fundamental aspect of Erthship building. Still, they have their advantages:
The idea of the passive heating involves the use of thermal mass and an insulative wrap around the thermal mass, keeping the heat from escaping to the outside. Thus, the thermal mass is heated by the sun during the day, and gives off this heat towards the living area during the night. This thermal mass could be anything from water to volcanic glass, anything massive enough to store heat, but the cheapest and most readily available material is still the good old dirt under our feet.
Wouldn't adobe be sufficient for thermal mass?
Indeed, it would. Adobe is an excellent material in this regard, just like superadobe or earthbags. But tires offer additional benefits: Each individual tire is like a brick in itself, making it fairly simple to stack compacted dirt as high as we want. Also, a tire wall can be built right on top of (undisturbed) soil, without the need of a foundation. For this reason, I would recommend a few courses of tires even under an earthbag wall. A well built tire wall is going to withstand fires, earthquakes, tornadoes, hurricanes, flooding, and even nuclear radiation. Not to mention, that once part of a wall, the tires are not a waste-product any longer, which would otherwise have to be burned, adding greatly to air-pollution. Also, once covered by various layers of plaster (usually cement or adobe), the rubber is not exposed to water or air, and so it doesn’t pose an off-gassing hazard, a frequently mentioned concern. Lastly, filling and compacting a tire with dirt, using a sledgehammer is a great workout, with results that can be felt and seen.
So if tires and windows aren't the hallmark of Earthships, what then?
Given the high desert climate of Taos, it is not surprising that Earthships evolved into being extraordinarily efficient at using water, and regulating temperatures inside. The building is heated by the sun, and excess heat escapes through the air vents in the roof. At the same time cool air is drawn through the cooling tubes in the northern wall, filling the living space with a fresh breeze. At night of course these vents are closed, to keep the warm air from escaping. Throughout the years this technique has been perfected to the point of meeting the ridiculously strict code requirement, of maintaining a constant temperature of 75°F (24°C) above the floor.
As for the water system, it is even more integrated, tying together the principles of rainwater harvesting, food production, and on-site blackwater treatment. At first, all precipitation is caught on the roof, and channeled into large cisterns. The dryer the climate the bigger these cisterns need to be, to store as much water as possible for the long rainless periods. From there the water is led through a set of filters into all the faucets for domestic use, including the washing machine, the shower, the boiler, even into the potable tap. Everything, except for the toilets and outdoor faucets.
Once we’re done using the water for washing, it is drained into the graywater planter, the long planting bin in the greenhouse, running along the southern window wall. There it provides the plants with moisture and the nutrients carried in it, while being filtered by the sediments inside of the planter. To enhance the effectiveness of the system, and to keep the water from becoming stale, a recirculation pump in the lower end of the planter continuously returns the water to the upper end. It is also here where the water for the toilets is pumped out from. This way, flushing the toilet is the third use of the same water, after washing and feeding plants. Finally, the same water is directed into the blackwater cell outside, where it feeds trees and bushes, hopefully the kinds that bear delicious fruit.
In my opinion, these two aspects are what make Earthships so wonderful. They alone are worth imitating and replicating. But is that it? Could you call your building an Earthship if it complies with these aspects? Or should you additionally grow food and build it with natural / recycled material? I'd say, sure, whatever floats your boat (and then call it an earth-boat). What I think is more important, is to utilize all our resources in the possibly most efficient way. And Earthships are on the right track doing that.
In my blog I went into greater detail outlining the pros and cons of Earthships, if you are interested. Also, it's worth checking out Earthship Biotecture, either visiting Taos, or just their website. As for the pictures, they are all mine, except for the two diagrams.
