…in Taos, New Mexico

by James Galletly from theownerbuilder.com.au

‘These are the most sustainable houses I have ever seen, and if these are the most sustainable houses, then this is how I should build.’ That was my first response to seeing Garbage Warrior, a documentary about renegade architect Michael Reynolds and his quest to build truly sustainable homes.

The Earthship is Michael’s answer to the challenge of sustainable housing. Put simply, Earthships are radically sustainable buildings, constructed with recycled materials. They are far from conventional, but they work, extremely well, and that is why Michael has been building them for over 40 years.

 

The internship

Earthship Biotecture, Michael’s design and build company, offers internships building alongside the experienced crew at the home of Earthships in Taos, New Mexico, USA.

I applied online and was accepted for their February 2012 internship. I later found out that being Australian worked to my advantage. Heidi Loehrer, the Earthship Biotecture intern liaison, told me that international applicants are given priority as willingness to travel shows their commitment. She also looks out for anyone in the architecture, building or engineering fields, applicants with experience in alternative construction or those who are planning to build their own home.

The internship involves working on a building site four days a week, one day volunteering in the Visitor Centre, and a few presentations on Earthship design and history.

Earthship basics

The essence of the Earthship design can be distilled into six principles; passive heating and cooling using thermal mass and solar gain; generation of electricity (usually via wind and solar); collection of water, which is common in Australia but not so common in the USA; treatment and re-use of waste water; food production within the home; and building with recycled materials. These six core principles are applied to each Earthship design with consideration for the local environmental conditions.

Additionally, Earthships are designed to be built with simple building techniques empowering people to build their own homes. A very appealing feature indeed.

The Towers

For the month of February our building project was The Towers. This building is an prototype designed for the urban environment. No Earthships have been built in urban areas, but Earthship Biotecture realises this is going to be necessary if they are to be a part of a sustainable future.

The Towers is a two-storey building with two independently accessed studio apartments. The apartments share a large south facing window and greenhouse area, and alternately could be used as a single home. Each studio space is formed by a rammed earth tyre circle and the attached greenhouse is predominantly built with can masonry.

The Towers is intended to be a demonstration building and rental, until it sells as a private home.

 

Can masonryOur first day on site we learnt one of the Earthship fundamental skills – can masonry. Mike Reynolds uses aluminium cans and glass bottles laid like bricks as a basic building unit. The cans are not structural; they act as space fillers. It’s the honeycomb matrix of cement mortar around each can that takes the load.

The use of cans creates a low embodied energy building material that is cost effective (free) and contributes to solving the environmental issue of waste disposal.

Laying cans is a simple technique with nuances of skill that come with time spent practicing (hence the value in interning). Wearing thick rubber gloves, you hand shape the mortar while laying the cans. Small handfuls, or pillows, of mortar are laid in a series along the wall, then a stretch of cans laid. Each can is creased on the underside and pushed into the mortar, making sure the end of the can aligns to the shape of the wall. It is important for load bearing strength that mortar surrounds each can completely. String lines can be set to guide the work.

I have tried can masonry without a string line, and found that the time it takes to run the string line is well spent and results in faster and neater work.

On our project, can masonry was used for the side walls of the greenhouse area. When cans are used on external walls a double can wall is laid with insulation sandwiched between them. The Towers used rigid foam insulation on the greenhouse end walls and pumice stone to fill the insulation space around the water tank.

Bottle walls are laid in a similar fashion to cans but have the added value of creating a stained glass feature.

Where one side of the wall is not seen all the bottlenecks face that side. When the appearance of both sides of the wall is important, cylindrical glass bricks can be created by cutting off the bottlenecks (with a tile saw) and duct taping two bottle bases together. Condensation inside the bottles can mar the beauty of these walls but I found out this can be overcome by not perfectly sealing the bottles allowing excess moisture to dry out over time.

Pounding tyres

Rammed earth tyres are the unofficial Earthship signature. The idea is simple: take a used car tyre, fill it with soil from the site and compact it with a sledgehammer. The result is a rammed earth brick encased in a tyre. These are stacked like regular bricks to form massive walls. The advantages of building walls with this method are; it’s low tech, it incorporates thermal mass into the house which is crucial for passive heating and cooling, the building materials are free and have zero environmental impact (assuming they are used tyres) and any soil type can be used.

The tyre pounding process is as follows. First lay out the entire course of empty tyres in place on the wall, adjusting them for spacing and alignment. Then fill them with loose dirt and push this up under the rim with your hands. The more dirt you can squish in, the easier subsequent pounding will be. To start pounding, work around the tyre swinging the sledgehammer through the middle of the tyre pushing dirt towards the tread. Compact around the outer ring of the tyre until the tyre wall bulges upwards, then fill the middle part of the tyre last. Each tyre is levelled within itself and in relation to the next tyre with a spirit level, allowing about 1.5cm tolerance.

When laying the next course of tyres, set the meeting point of two tyres over the centre of the tyre below. Invariably the joins will drift off centre and it will be necessary to leave a space somewhere in the row in order to correct the staggering. This space is filled by squashing a tyre into the gap. This will take some force and maybe a hit with a sledgehammer but it will go in and once in place is pounded like a normal tyre.

On our first day we interns averaged about five pounded tyres each. Within a week we had increased our speed to around 10 tyres each a day. Phil Basehart, our foreman, assured us that an experienced tyre pounder could finish 20 tyres in a day. Once we settled into a rhythm and our pounding muscles developed I could see how this would be possible.

Tyre pounding is best done as a team activity, with some people pounding and others bringing loose dirt and more tyres, and rotating jobs throughout the day. The increased output and shared labour of teamwork turns the task into an enjoyable and satisfying day at the office.

Bond beam

The previous intern group had also worked on The Towers, so when we arrived all the tyres for the first level had been pounded. The next step was to lock the tyre wall together with a continuous bond beam.

A wooden beam can be used for this, but we used a poured concrete beam. This is easier for curved shapes, is stronger and lasts longer. The beam is poured directly into a form built on the tyre wall. The form is made by laying two parallel lines of can masonry. The advantages of cans over wooden forms are: quicker construction time, it is better suited to curved shapes and the cans are left in place, becoming part of the building.

Pouring the beam was an all day job for six workers. We had one person mixing concrete in two mixers, two people running wheelbarrows and passing buckets up to a line of workers on scaffolding and one person dedicated to agitating and levelling the pour. The hardest part of this task was the lifting of concrete to the scaffolding.

VigasFor roof supports, Mike’s designs tend to favour the use of vigas. These are large rough hewn logs. In New Mexico, they are a locally sourced material that can be self-harvested and require minimal processing.

Prefabricated roof trusses can be used for Earthship roofing and are actually cheaper when compared with purchased vigas, but this option needs to be weighed against the added environmental cost of a fabricated and transported product and condensation issues that can occur in the roof space. Because Earthships are commonly built in areas with extreme outside temperatures and have constant internal warmth, the air in the roof cavity often forms condensation. With vigas, the roof is fastened directly on top and the logs left exposed underneath, eliminating the roof cavity altogether.

The Towers design used pine vigas as a ceiling/floor between the building’s levels, as well as on the roof. The vigas sit directly on top of the bond beam and are connected with rebar spikes.

We hired a crane to lift the vigas into place and in two hours all 10 vigas were done. Where a crane is not an option vigas can be lifted manually and walked up the earth berm that surrounds the tyre wall. The logs seemed so massive I couldn’t imagine lifting them, but I checked out the Earthship Biotecture YouTube channel and saw that it can be done.

Before we lifted the vigas we numbered them in accordance with their roof position, and drilled them to accept the rebar spikes. Accurately measuring the placement of the holes to accept the rebar is critical as once the vigas are hoisted on the roof it’s a hassle to re-drill or persuade them into place. Variation in diameter means shimming the logs is necessary to obtain a flat surface. After we achieved this we nailed in 25x200mm pine floorboards onto the vigas. The underside of these boards is the first floor ceiling and the topside will be cement plastered to form a flat floor, with added thermal mass.

Windows

Along with working on The Towers I spent a few days with a different work crew doing some maintenance on a 15-year-old Earthship, which the owners did not live in full time. We were replacing the wooden framing in the glasshouse and adding mullion caps for future weather protection.

Over time weather damage had rotted the wood around the glasshouse windows. This issue arises as the glasshouse is exposed to the full brunt of the weather all day every day, with no eaves for protection. The job was to pull the glass out, replace the wood where it was no longer structurally sound, refit the glass and then add mullion caps. These caps are sheet metal strips fitted over the wood and sealed to prevent any water penetration. The metal strips are sealed with a line of butyl tape (a non- hardening, white or black, tough, elastic material which has excellent sealing properties to metal, glass, and plastic lap points) along the inside edge and roofing screws with rubber washers are used to fasten them in place. All new Earthships are now built with mullion caps and specific hardy wood species for the window framing.

What I learnt

An Earthship built in the USA by Earthship Biotecture, to lock up, will cost a similar amount to a good quality conventional home, approximately US$1845 per square metre. The difference is that an Earthship is a self-sustaining, off-the-grid home with greatly reduced living costs.

If you were to owner build, providing all your own labour, this could save around 35%. Another cost saving area is designing down and augmenting the systems. A number of Earthship owners told me they get by comfortably on smaller electrical systems than those in standard Earthships (although these guys were all old hands at off-the-grid living). The Earthship design can also incorporate other alternative and energy saving technology, e.g. by adding a dry composting toilet the water treatment system is greatly simplified.

The advice I received on owner building an Earthship probably holds true for all owner builder endeavours; start with a small, simple design that can be added onto at a later date. Earthships lend themselves particularly well to this modular approach to building and by building the first stage you become experienced in all the aspects of construction.

The internship is not a structured learning situation so you get out what you put in. Copies of all the Earthship books and videos were available for interns. Taking advantage of this definitely enhanced the learning experience. The Visitor Centre also has floor plans of Earthships built around the world, and seeing how the designs change for different climates is another valuable opportunity.

Interns live in an Earthship while in Taos. We also visited numerous Earthship homes and rentals. I feel this part of the experience was equally, if not more valuable, than the building. It’s one thing to read about a design, but another to actually see and feel it in person. I knew I wanted to build an Earthship, but I had not considered whether I wanted to live in one. Visiting so many helped me envisage and understand Earthship living.

Although in one month I did not experience every part of the building process, the internship gave me a good working knowledge of the style of building and from this I would definitely be confident to start building my own.

For anyone else considering building their own, I would say that interning with Earthship Biotecture is not a necessary step, but it is a valuable learning experience and one that would result in more confidence in, and a better working knowledge of, the design. Not to mention an increase in the necessary building skills. These factors are ultimately going to give you a better finished product.

Resource: Earthship I, Earthship II and Earthship III

Books by Michael Reynolds. These books contain all the how-to information and design theory for building your own Earthship. These books are now old and actual designs in the books have been superseded but the fundamentals are still relevant.