Throughout the last year Michelle and I have been searching for green building methods that use little to know grid energy for space conditioning and electrification. So far we have seen a straw bale house, and underground concrete building, adobe brick and Michelle has extensively studied the envelope of the passive haus standard in Germany. All of them provided various pros and cons and everyone it seems has an opinion on the subject which we have discovered can vary from the logical to the insane. While we were in Teotiucan I was surfing the net and came across the Earthship website where I discovered a week-end seminar on Earthship construction. An Earthship is the brainchild of the eccentric architect Michael Reynolds. It is basically a house made of rammed earth and tires, usually in a U shape with the backside of the U earthshelter (i.e. burried into a hill). The dates for the week-end seminar lined up perfectly with our trip through New Mexico and Michelle and I decided that it was an experience worth attending.
We arrived late Friday night at the earthship headquarters which of course is an earthship. We watched Garbage Warrior, a documentary based around the earthship creator Micheal Reynolds and his struggles with the building codes in New Mexico. It is a great movie and paints a perfect picture of Michael, who is quite the character. The rest of the week-end was a mix of lectures by Michael about the history of the Earthship concept, how the structure goes up, how the thermal mass works to keep the earthship warm in the winter and cool in the summer, how the energy and grey water systems work, etc. We also spent a good part of the week-end pounding tires! Man is that a good workout.
The earthship inventor, Michael Reynolds decided after graduating from Architect school that the world did not need any more architechs designing standard building envelopes that were energy hogs, and as suseptable to grid failure as the utilities. Seeing all of the large landfills, peak oil, massive and global warming on the horizon he set out to start building green buildings out of what ever he could find. His first buildings were as crazy looking as the materials that he used. Michael started with bricks made from six beer cans. This made sense as there was no recycling back then and he loves to drink beer. He then tried to build with beer cans without making bricks but using the individual cans as bricks. Both of the concepts worked well structurally but did not provide the thermal mass that he was looking for. A short while after he started these crazy building projects the architechts association withdrew his license indefinitely. With nothing left to loose and a little more than a couple of pennies to rub together he decided one day that he would build a house out of tires. As weird as it seems you can’t argue with his logic. As Micheal says, they are indigenous to the planet, they are virtually indestructible, waterproof, have a big footprint and basically make the best brick in the world. Typically the homes are designed as a large U or a series of U’s parallel to each other with the open part of the U facing south in the northern hemisphere, and north in the southern hemisphere. The orientation of the U’s is based on maximizing the solar gain that the house receives. Once the shape of the house is determined the U’s are draw on the ground, and a survey of the land takes place so that it can be flattened out. Next the first row of tires is placed forming the U’s which means that it is time to start filling the tires with dirt and compacting the dirt with fledge hammers. This is by far the hardest part of building one of these structures as it is intense and slow physical work. We were told that if we wanted to determine the amount of time it would take to build the walls to assume that one man could pound 20 tires a day which is a drop in a bucket considering the average earthship has 1000-1500 tires. The tires are stacked in an offset pattern similar to traditional bricks, the difference being these bricks weigh 150 kg! As the tire wall goes up earth is burmed around the outside with an insulation skirt about three 1 meter away providing frost protection and support to the tires from the outside. After the walls are built trusses are spanned and a greenhouse is added to the front of the building. The roof is insulated to R 70 and sloped in order to capture rain water for the inhabitants. For those of you who have a good understanding of building you may have noticed that there was never a foundation, grade beam or piles driven to support the building. This is one of the many advantages of this building. Because the tires are very wide they have enough surface area to span the load and do not require a footing. The walls in the building are finished with a cob mixture which covers the tires and beautifies the building. Michaels goal for an earthship has always been to make them completely self contained with a very small environmental footprint. For this to happen he had to come up with ways to deal with grey water, sewage, electricity, and thermal energy.
The thermal energy completely provided for by the sun via the southern greenhouse. The thermal mass in the tire walls store the heat from the day and release it at night. The highly insulated roof ensures that minimal heat is lost to the environment.
Greywater is any water is considered waste water that contains no sewage. In the earthship water that is captured from the roof is stored in on site cisterns where it is drawn, filtered and used for sinks, showers and dishwashers, this water (grey water) is sent to a biological water treatment cell located in greenhouse where plants clean the water. Excess water in the grey water biofilter is then collected in a sump and sent to the toilet. After the water is used in the toilet it is considered black water and treated in a different system.
Black water is any water that contains sewage. This water is sent to a septic tank where the solids and liquids settle out and then it gets pumped into a similar biological cell to the grey water cell which is planted with perennial fruit trees. This cell is lined with thick poly to protect the ground water and is equipped with an overflow tank which can be pumped if there is any additional sewage left over. The overflow tank is placed there to satisfy the building codes and to date no system has flowed into it. Michael also mentioned that water has been tested after going through the sewage cell and it is always clean.
Because the earthship was designed in the desert where less than 300mm of rain and snow fall annually it is important to ensure that the water is used as many times as possible. With the aforementioned systems water is used
For drinking, washing, cooking ect.
To feed a food bed in the front greenhouse
To provide flushing water to the toilet
To feed a perennial black water bed providing fruit trees.
Electricity is provided for with solar PV, wind generators or micro hydro depending on what is available on site. The system is a standard power system but interestingly enough it is one of the first components to be installed in a house as it provides the power for the saws, drills and cement mixers. This allows them to build anywhere there is renewable energy!
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