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 🙂