How to build an earthship - Our adventure in New Mexico
Throughout the last year Michelle and I have been researching green building methods. So far we have visited and helped build strawbale houses, spent time in an underground concrete building in Denmark, checked out adobe brick and visited the Passivhaus Institute (Passive House) in Germany.
Surfing the net recently, I came across the Earthship. An Earthship is the brainchild of the eccentric architect Michael Reynolds. It is basically a passive solar house made of tires, which have been rammed with earth. The backside of the house is buried into a hill. It turned out that there was an upcoming workshop in Taos, New Mexico. As we were travelling from Mexico to Washington, the dates aligned nearly perfectly with our trip and we decided it was surely a sign to go and check things out.
A Little History of Reynolds & His Earthship
The Earthship inventor, Michael Reynolds decided after graduating from architecture that the world did not need any more architects designing standard, energy inefficient buildings. Seeing all of the large landfills, peak oil and global warming on the horizon he set out to start building green buildings out of what was available abundantly – trash. Reynolds started with trying to develop bricks made from beer cans. This made sense as there was no recycling at the time and he loved to drink beer. The concept worked structurally but did not provide the thermal mass that he was looking for. Reynolds still uses cans in his construction, but in non-structural walls and fences instead.
As he continued building unconventional structures, his professional association lashed out and removed his architect designation. With nothing left to loose and a only a couple of pennies to rub together Reynolds had an epiphany - to build a house out of vehicle tires. As weird as it seems you can’t argue with his logic: "they are indigenous to the planet, they are virtually indestructible, waterproof, have a big footprint and basically make the best brick in the world". Reynolds' goal for his Earthship was to make it 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.
General Earthship Construction
Typically the homes are designed as a large U or a series of U shapes parallel to each other with the open part of the U facing towards the sun. The orientation of the U is based on maximizing solar gain, in our hemisphere, south. The first row of tires is placed forming the U shape and then the tires are filled with dirt and compacted with a sledge hammer.
The tires are stacked in an offset pattern similar to traditional bricks, the difference being these bricks weigh 150 kg each! As the tire wall goes up earth is pushed up against the wall, followed by an insulation skirt and then further bermed with dirt. After the walls are built trusses are spanned and a greenhouse is added to the front of the building.
The roof is insulated to R70 and sloped in order to capture rain water for the inhabitants. For those of you who have a good understanding of building practices you may have noticed that there is no foundation, grade beam or piles driven to support the building. This is one of the many advantages of building with tires. The tires are wide enough that they can 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 makes for a beautiful natural finish.
We arrived Friday late afternoon at the Earthship headquarters which is, of course, an Earthship. There were about 50 other participants from all over the world, a couple had even come all the way from Japan. Reynolds introduced himself to the group, and after a BBQ we watched the recently released movie documentary Garbage Warrior. This documentary is about Reynolds, his earthship design and particularly his struggles with the regulatory authorities while trying to develop self-sufficient, off-the-grid experimental structures in New Mexico. It is a great movie and paints a perfect picture of Reynolds, who is quite the eccentric character.
We spent most of Saturday listening to Reynolds give lectures and talks. He spoke about the history of the Earthship, including stories of all the failed concepts – which was incredibly entertaining. He spoke of the current earthship design, how the structure is built, and how he balances thermal and insulation for complete thermal comfort. One of the most interesting and ingenious designs is the water system and biological cleaning cells that Reynolds has developed (more details on those below).
Sunday started with a tour of the Greater World Earthship Community. Basically this is an “ecovillage” with all houses being Earthships. Interestingly the site chosen is actually an old gravel pit. We thought this was brilliant – typically we humans always want to build our homes in the most pristine location. Here is an example of building a community with the goal of reclaiming that land. More of us should be doing this. And of course, the goals of the community are to be self-sufficient and take full responsibility for land / water use, supplying their own power and as much as possible, taking care of their own needs.
The interior of the homes were beautiful, we loved the organic and natural curved look of the interior cob finish. Some homeowners had been incredibly creative using glass bottles in the intererior cob walls to create beautiful glass mosaics. Another great idea was to build tile using panels from old appliances found at the dump. The ingenuity and use of recycled materials was extremely impressive.
We loved the idea of integrated greenhouses on the south side of the building. These greenhouses provide numerous functions: fresh food, clean the air, beautify the space and are also used in the water-processing system.
On Sunday afternoon we got our hands dirty and helped out with building an earthship as there were several buildings in construction at the Greater World. Our first rotation was “tire pounding”. This involves placing a tire on top of the previous row being sure to offset it for stability. Next, place cardboard inside to create a cover over the bottom of the tire so that the tire can hold soil. The next step is long and tedious; fill the tire with dirt, pack it with a sledge hammer, fill the tire with dirt pack it with a sledge hammer, fill, pack, fill, pack...... The key is to ensure that you compact the earth into the sidewall of the tire, which requires a little aim and practice. If you are inexperienced, one tire can take about one hour to finish – seriously. This is by far the hardest part of building one of these structures and is intense and slow physical work. We were told that a good, strong worker could pound on average 10, maybe 15 tires a day. With a small building using between 1000-1500 tires, that is an incredible amount of hard physical labour and time.
After the tire experience we decided that we would try making cob and help build a fence being built out of beer bottles and cob. Reynolds makes everything out of cob & garbage! Again, quite ingenious as using cans reduces the amount of cob required to build the wall.
We really enjoyed the workshop, and if you are considering building one or learning more about these buildings, consider either attending a workshop or volunteering on a project. There are more and more projects happening, especially in Canada – check out the Earthship Canada Network for dates and locations.
With the Earthship being designed in an extremely arid climate (less than 300mm of precipitation per year) they have developed very smart water-use design – one of our favorite things about these buildings!
First off, the roofs are sized and water cisterns designed to capture every last drop of water (including snow) that might fall throughout the rainy season. Water is then gravity-fed (or pumped) to a water filtration system and into a pressurized tank to supply water for drinking, bathing or washing dishes.
After being used once (bathing, drinking or washing), the water is called greywater. Instead of being sent directly to sewer or septic, as done conventionally, this greywater is diverted to a biological water treatment cell – essentially a raised garden bed located in the greenhouse, designed to remove the nutrient out of greywater. Why feed plants fresh water when they thrive on greywater? Once the greywater has passed through this cell it is clean enough to use again, but this time to flush toilets. The water is collected in sump and pumped to the toilet tanks for flushing.
When you add human waste to water it becomes sewage/ black water. Typically this is sent to a septic tank/field or the municipal sewage treatment plant. In the Earthship this water is sent to a septic tank where the solids settle out and the fluids are pumped into another biological cell for processing. This cell is often located outdoors and is planted with perennial fruit trees and shrubs. This cell is lined with thick poly plastic to protect the ground water and filled with gravel and soil so that the water never sees the light of day. The cell is equipped with an overflow connected to a pump-out tank in the event that there is more fluid than the cell can deal with. Reynolds, however, claimed that this has never happend. He admited to us that the real reason to place the pump-out tank on the end of the cell was simply to satisfy building codes.
With the re-use systems employed in the earthships, every drop of water is used four times:
Rain water is used for drinking, washing, cooking ect.
Grey water to feed a garden bed in the front greenhouse which doubles as a grey water cleaning system.
The cleaned grey water is then pumped to the toilets which then becomes black water.
The Black water is used to feed a perennial trees which cleans the water and grows food.
This process completes the nutrient cycles which makes these systems ecological wonders! Another way of looking at a system that can reuse water four times is that your preceived rain fall is 4 times as high, or 1200mm instead of 300mm.
Given the high thermal mass, the design to capture as much sun heat as possible and the fact that the building is partially covered by earth, this house needs little-to-no mechanical heating system. The large thermal mass in the walls stores the heat from the day and releases it at night. Also, a highly insulated roof and earth-sheltered north side ensures that minimal heat is lost to the environment. The solar radiation that is captured on the south facade not only keeps the house warm, but also drives air exchange through the operable windows keeping the indoor air quality high.
Given that no mechanical heating system is required, the electrical needs of the building are extremely low, and electricity can easily be provided for with solar photovoltaics, wind generators or micro hydro depending on what is available onsite.
With greywater being diverted to a bio-cell, an added bonus is the ability to grow food – without even stepping outside! The current industrial food system is hundreds of time more environmentally destructive that even the oil sands, and therefore any small part we can do to remove ourselves from this system has a large impact. Nevermind that we can choose to grow organic and there's no questions that our greenhouses will nourish and enhance our health.
And the Verdict is...
Interestingly, the similarities between the climate in Taos, New Mexico and Alberta are striking:
similar strong winds, epecially in the prairies
temperature extremes (they might get down to -20 deg C, although we might get a touch colder)
similar solar resource
Overall we think that the concept of earth-sheltered buildings is fantastic and could definitely be applicable to our home climate of Alberta, especially if you live on the plains where the cold wind blows hard six months of the year. However, these building do need to be properly designed, with correct orientation, placement and drainage considerations. Serious issues could result if good design is not used.
The advantages of this type of building are numerous: they will never drop below zero (being earth-sheltered
will stay at ground temperature, around 4 degrees C), need little-to-no additional mechanical heating system, have an attached growing space, are robust, on-site processing of runoff water, greywater, and black water reduces the environmental impact, and in addition, rubber tires are often free, or even sometimes end-users can get paid to pick them up.
One of my favorite quotes by Bill Mollison is: “If we don't meet the needs of a system from within, we pay the price in energy and pollution”. The Earthship is one of the few buildings we have seen that actually sets out to acheive this goal!
We don't think that there is an Earthship in Alberta - but we would be surprised if a project didn't start up in the not-so-far future.