What is different about “Global Model” Earthships?

The modern incarnation of Earthships seems to be going under the banner of something Earthship Biotecture calls the “Global Model”. There is very little documentation of the “Global Model” (I’ll get to that point a bit later on in this post), so here’s what I’ve been able to piece together. I am sure there are many more details, but what follows are strategic issues that matter to me. If you know more about the “Global Model” you’re welcome to add more insights in the comments to this post.

 Evolution

The most important lesson I’ve learned in tracing the Global Model is that Earthships, as designed and built by Michael Reynolds and Earthship Biotecture, are a work-in-progress. They keep changing, removing past mistakes, improving on old ideas, introducing new ideas, etc. This implies that there is no “ultimate” Earthship design – it changes (and must change) with context (cultural, economical, ecological, etc.). It is ultimately up to me to make the choices that best fit within my life context and best serve my needs. Don’t go looking for a manual on how to build an Earthship – there is no such thing. Even the original Earthship books by Michael Reynolds (though packed with valuable information) have obsolete information in them. You are better off understanding the underlying principles, studying as many Earthships as you can find and then taking responsibility for filtering and applying that information to your build. My interest in the Global Model is not as a(nother) template but rather as a reflection of changes and refinements Earthships have undergone. I am curious to see how the underlying principles have been challenged and how those challenges have been met.

 One Big U

I think that the most prominent change has been in the core structure of the Earthship. Originally an Earthship was built using connected U’s built from rammed tires.

Global Modal Earthships seem to have done away with that and instead are built with one large encompassing U built of rammed tires creating one large internal space. Then, that one large space is further divided into smaller spaces using internal walls (usually from concrete-can walls).

I can think of numerous reasons for this:

  1. Architectural Design Freedom – rammed tire walls are not a flexible design element – they are massive and structural – they are an overkills for internal non-structural walls. Removing them from the inside makes it easier to divide the internal space.
  2. Less Work – rammed tires are hard work much more difficult then concrete-can walls. They take longer to build (given the same manpower).
  3. Faster Closed Building Shell – there are two main phases of construction – before there is a closed shell (roof + glazing + skylights + doors) and after there is a closed shell. Less tires means you can get to a closed shell faster – much faster. Since Earthship Biotecture also build Earthship shells in blitz-projects – it makes sense for them to strive for a quick-closed-shell.
  4. More Floor Space – Though it isn’t a drastic difference – replacing thick tire walls with thinner concrete-can walls leaves more open floor space.

The price:

  1. Concrete Buttresses – concrete pillars attached to the rear wall have now been introduced (instead of the massive rammed tire walls) to provide structural support for the long rear wall – this is a whole new skill set (suddenly there are stories of forms breaking and concrete flowing around the building site).
  2. More Concrete – much more concrete is now used in the project – both in the buttresses and in the internal walls.
  3. Thermal Mass – though I don’t think it is a high price I do believe this results in less thermal mass in the house (though I may be wrong here – because concrete may be more dense and therefore have the same thermal mass as a thicker earth wall!).

This change seems to be coupled with additional and interesting structural changes.

Greenhouse Separation

In the original Earthships the greenhouse was bordering on the living spaces.

Though it is mentioned only in passing in the original Earthship books it seems that in the Global Model the Greenhouse corridor is almost always separated from the living spaces by an additional (mostly glass) wall.

This one was a hard nut to figure out. My understanding is that this configuration provides better climate control in the living spaces. What follows may be totally wrong … but this is the best I have to offer so far. The greenhouse, besides it’s inherent function as source of food, is also a heating device – especially in the winter when it gets direct sunshine (when it can it heat up more then it does in the summer). When the Greenhouse and living spaces were one – whatever happened in the greenhouse directly effected the attached living space. Separating them introduced a better level of climate control. My gut tells me that the greenhouse also had at least two unwanted effects. One is increased humidity due to the abundant plants. The other is obnoxious smells due to the grey water presence (I am guessing that smell problems come not so much from the grey water processing but rather from the attempt to store it for reuse – flushing toilets). So by separating the greenhouse from the living spaces all three problems were mitigated:

  1. Heat – the heat in the greenhouse can now be controlled by (a) letting cool air in from the low-placed operables ad (b) by letting warm air out through skylights. Heat in the rooms can be controlled by (a) windows in the separating wall that let warm air in from the greenhouse and (b) skylights which let warm air out and (c) ventilation tubes that let fresh air in from the outside (more on later on).
  2. Humidity – increased humidity in the greenhouse can be vented out through its skylights without automatically effecting the living space.
  3. Smells – can also be mitigated through ventilation before they take over the living space (though personally I would not contain grey water … more on that in a future post).

The Price:

  1. More construction – a new wall requiring footings and framing has been introduced.
  2. More Glazing – assuming you will want to let as much light in to the actual living space be prepared to pay for a lot more glazing (I still haven’t decided if simple one-pane glazing is enough or more thermal-double-pane glass should be used).

 Roof

There are two changes I have noticed in the roof. One seems to be more consistent the other less so.

The first is the direction of roof rafters. In the original books rafters ran in an east-west direction.

In the Global Model it seems that rafters are now being installed in north-south direction.

This change seems to be related to the One Big U approach – which have a limited depth but unlimited length. So now rafters can be laid to enclose a space of almost any length – the longer the space the more rafters are installed.  The price is that- north-south rafters need a front (south) frame onto which they can be laid – that frame comes in the form of the wall that separates the greenhouse from the living space.

The other change that seems to be prevailing is that the roof now has single slope – it seems that new models no longer have the raised greenhouse lip that was originally described and implemented almost as a trademark of Earthships.

I am not sure this is a change in design strategy but with the north-south oriented rafters it makes sense (to me) that the roof is one single slope. Also, I have to admit, I never really understood the importance of the original design – other then create a larger opening – which, to my understanding, can be achieved with roof that slopes down to the north – so that the south end is raised.

 

Experimentation

To summarize and re-iterate the process of evolution of Earthships I feel it is important to highlight that Earthship Biotecture seems to be a group constantly exploring new directions seeking new solutions that further complement their core direction. Some of these experiments may never find widespread adoption, some may only lead to further inquiry. I haven’t seen things such as indoor cisterns and jungles (Earthships Volume III) in many Earthships. I personally feel that their solar toilets are way too complicated and expensive compared to the dirt-cheap (and renewing) composting toilets we are already using.

The point  is that everything about Earthships needs to be filtered and contextualized. There are no “global” solutions, there can be no “global” Earthship model, there shouldn’t be. There should be constant striving for creating better and more sustainable solutions and open sharing of build attempts (both failed and successful ones).

This post is a first in our effort to understand and process the latest and greatest that Earthship Biotecture have to offer. We continue to explore other self builds and their experiences. Ultimately this will lead to an adaptation of an Earthship that will be best suited to us.

If you have any further insights into “Global Model” or other core Earthship workings, please do take the time to leave a comment. We would appreciate it greatly 🙂

 

8 Replies to “What is different about “Global Model” Earthships?”

  1. It also seems that the ventilation strategy has been changed. If I am not mistaken then a large greenhouse/corridor skylight is now installed and I am not seeing skylights above the living spaces.

    It also seems that ventilation tubes penetrating the living spaces from the rear are a source of fresh air. Every time I have run into these they are explained as cooling tubes – a kind of natural air conditioning. But, I was first introduced to this as a source of fresh air that is warmed by passing in long underground tunnels (in the winter these tunnels warm the air, in the summer they cool it).

    So I am beginning to think that the ventilation tubes are a must. If so it seems that one is needed in every living space – or at least every other living space with some kind of ventilation path between two rooms. That is becoming an expensive feature.

    Also, I am still not convinced that that would be enough. I am still wondering how (stale) air can recycle out of the living spaces. Actually, now that I think about it I don't understand how the air cycles between the greenhouse (which is typically warmer) and living spaces.

  2. Thank you for a great article. We are currently building an Global Earthship with dirtbags in Africa.

    Modifications:

    Seeing that we living far away from a source of tyres we decide to use dirtbags.

    We did use small arches for strength, a bit like the original Earthships.

    Using air filled recycled bottles for isolation in the hill at the back.

    Will use a bio-digester for cooking.

    The rest is as close as possible to a Global Earthship, finances and materials permitted.

    Tips and volunteers are welcome.

    Ludwig and Retha
    http://www.aardskip.com click on "blog" to follow our progress.

  3. I wondered many things about the multiple U design. They went to packaged claiming it was cheaper. Maybe that was it: labor was cheaper to pound fewer tires. I wondered if the wall would collapse if somebody tackled somebody into the wall. The east and west walls aren't going anywhere. If you span vigas across, they can't move east to west. The bond beam is very rigid and will also stabilize the whole top of the wall, not to mention the later development of driving spikes into the wall near the top. I want more thermal mass, not less, so I like multiple U's, but multiple U's won't make very wide rooms. Concrete has a slightly higher thermal mass value since it's more dense, but we're only talking about 1.5 vs. 1.3 (water is 4.0). If you have a bottle/can wall, then it all must be equal. So if the tire wall is 3 times thicker than a solid concrete wall, the tire wall would have 2.6 more capacity to hold thermal mass. Also concrete will conduct temperatures, so if the concrete is exposed to outside anywhere the wall will be real cold in winter as the heat in the room is allowed to move easily to the cold location.

    I didn't give much thought to the grey water smell, such as in the living space. The glass everywhere is not really to separate smells, but to keep the place warm, creating air locks, yet allowing in solar gain. If the room is not leaky and you have insulated glazing, then it will automatically get like 15-20 C temperature gain without considering solar gain. If it's too hot, you need to open the cooling vents.

    Catching the solar gain and somehow trapping it is the key to an earthship. The angle of the greenhouse was somewhat of an issue in vol. 2, because the south-facing roof will catch more melting snow, but at the front it starts restricting solar gain. What can you do? Raise the roof so the front of the rooms is already high? Make the greenhouse shallow? In vol. 2 days they tilted the greenhouse up to catch more sun. Without sun, the place will be colder. In the old days they did not use metal roofing.

    Solar toilet is not really that "expensive". Actually they don't sell the plans anymore. If you're in a place that gets a lot of sun, then you just dump the contents like ash in a stove. A composting toilet may attract flies. A solar toilet does not allow the possibility of hatching flies. EB doesn't support solar toilets or sell the designs. I'm making my own (2-3) in one building.

    Also the N-S vigas in the GM overhang the north thermal wrap.

    As far as glazing goes, it probably depends on your climate. Windows don't have much insulative properties. If it's cold and you have single pane windows, almost all the heat will escape. If you're in a warm climate, maybe that's OK. The point of insulated glazing is to allow solar gain in but to trap the warmth. There are different kinds: double, triple, argon filled, etc. Multiple greenhouses create airlocks. A wall in a regular house might have R-20 or R-30, but a single pane window is probably less than R-1. Very good insulated glazing might be as high as R-5. 5 times 3 is R-15, which is getting close to a regular wall, considering all the glass will yield much more solar gain than a regular house and much more thermal mass than a regular house. Another option is to put curtains in the living space over the glass to trap the heat so it doesn't escape at night.

    Here is a quote from another web site: "For instance, a single pane glazed window has an approximate R-value of 0.85, while a double pane glazed window has a value of 1.5 – 2.0, a low-e double pane glazed window has a 2.4 – 3.0 rating and a low-e double pane glazed window using an argon gas fill has a 2.7 – 3.6 R-value."

    A room with an entire wall of glass with 0.85 will be cold in anybody's book. If you're in Jamaica, maybe that's a good thing. A standard insulated wall might have R-20. Even that without solar gain or heat might feel kind of cold in winter. With 3 layers of insulated glazing, let's say we got 3.5. 3.5 time 3 is R-10.5, which is starting to get close to a regular wall. Solar gain is powerful. Catch it during the day in thermal mass. Trap it in water or use curtains to prevent the escape. insulation behind the tire wall prevents the escape of the heat also.

  4. Thank you very much for this, IAMRONEN.

    After advocating earthships for seven years (and buying books and reading and viewing videos extensively), I’ve become disenchanted with the earthship concept.

    Why? Two reasons: First, I’ve concluded that the advent of the rocket mass heater has made the earthship concept unnecessary as I now can heat my home inexpensively. Secondly, I’ve become disgusted with the greed and elitism of Michael Reynolds’ Biotecture organization that now has the gall to sell plans, water modules, services, and more at the most unreasonable prices. I refuse to deal with them.

    BTW, a large earthship built recently in New York State by a young couple (with the services, plans, products, and participation of Biotecture) cost more than $300,000. This has nothing to do with the philosophy or practice of the green building movement.

    1. I haven’t been following earthship happenings for many months. I too feel that something about the concept is out of tune.

      In trying to figure out the reasoning behind some earthship design choices my research brought me to this: http://bhudeva.org/blog/2012/01/23/building-an-earthship-in-a-cold-climate-stop/

      Having lived with rocket stoves for 3 years now I am very much looking forward to a house that needs no additional heating.

      Thank you for spending time here and leaving your comment.

      1. Greed is the route of the majority of evil on planet Earth. Earthship Biotecture is becoming greedy. Be advised, do your own research, ask around, get informed and don’t hate or judge in the process. Were all human and capable of falling short, time will tell what the next chapter in sustainable living is but for now I’m building an earthship using my own design and my own ideas which will be shared open source for all to benefit, learn and grow.

  5. I did many energy models on various models and different depths. I was targeting a build in a cold climate. Basically Mike R. was right in the first book that multiple U’s has more thermal mass; more thermal mass has more heat storage and will get you through colder periods. Don’t kid yourself: the GM has less thermal mass than multiple U’s and will have higher highs in summer and lower lows in winter. It could be acceptable in a moderate climate. I found in a cold climate that it’s simply unacceptable. More thermal mass is just more heat storage. Why did they migrate to GM? Mike R. explained that they went from multiple U’s to packaged model to save money: less labor. If you’re hiring labor, it’s easier and faster to get the walls up. It might be OK, but you have to face the facts that less thermal mass means less stable temperature. More insulation helps some up to a point. You still get higher highs and lower lows compared to having large amounts of mass. A fact is: if you want a lot of mass, you have to start getting creative where to place it. Thermally it performs better, but design is less flexible.

    Also, having living space glass creates a thermal buffer between the outside and the living space. It costs a little more, but the bedroom will be warmer on winter nights. If you’re in a warmer climate, then it’s probably not needed. If you’re in a cold climate, it’s an relatively inexpensive way to trap heat. The room is more like a solar oven. During warmer times you need to be able to release any heat building up in the room.

    A GM just with a 2nd greenhouse will still be quite cold in a cold climate. You need to keep adding thermal mass and more buffer zones. The internal glass should be single pane tempered glass to allow as much solar gain into the living space since 1 standard pane of glass will filter out about 15% of the solar gain. The outer layer is probably good to use double insulated glazing, but internal glass should be single pane so heat is not released from zone to zone by air convection. The air buffering slows that kind of temperature loss and the heat loss is through conduction through the glass which is slower.

    People have to make their own decision what to retain and discard in the GM based on their climate and financial means, but if you’re in the developed world, it might be hard to get an architect that will draw up a custom ES. The GM is a far cry from Mike R.’s own ES mentioned in the back of vol. 1 which only cost $32k in 1990 dollars. Anyway, I’m thankful for all of Mike’s sharing of info.

  6. I agree that MR/EB seems to have fallen in the way of capitalist greed; however, the Earthship as a product is his innovation, and he does have a right to make a living from it. He also has the responsibility of providing financially for those who are employed for EB. While donations to their projects may be written off as charitable tax breaks (I would have to double check that), at no point have they ever claimed to be a 103(c) / nonprofit. It’s generous in and of itself to have made public the knowledge of how to build them. The books are still worthwhile to someone who is determined and willing to do it themselves, even if they are slightly outdated.

Leave a Reply