Category: Earthship

Earthships & Living Roof

Roof harvested rainwater is the primary (and often by design the only) source of water in an Earthship. One of the defining features of Earthships is therefore a sloped roof designed to collect rainwater. Water is accumulated in large underground (or sometimes indoors) cisterns, passed through a series of gradually refined filters and is then pressurized with a relatively small, simple and low-energy-consuming pump. This entire system can be complicated and expensive and is an all or nothing deal. There is no point in having a rainwater harvesting roof if you can’t store the water. There is no point in storing the water if you don’t or can’t use it.

We are questioning including this feature of Earthships in our plans and are considering in its place a living roof (earth and plant cover) as a preferred solution.

Roof Longevity

The primary function of a roof is shelter. It is so obvious that it is often compromised and overlooked. Most modern roof systems are actually very poor when it comes to shelter … they require maintenance and too often complete overhauling. Our architect took us on a day-trip which included very old houses with thatched roofs (once a common roofing practice, today a rare art) – If I recall correctly this roof was over 80 years old,s built of a natural and insulating material (straw) and can outlast the structure beneath it. Most modern roofs don’t come anywhere need this kind of longevity and require major maintenance every 5 to 10 years.

Earthships (especiall Global Model) seem to most frequently use something called “Propanel” roofing … which is basically a sheet metal roof usually made of steel with various protective (and rainwater safe) coatings. Some Propanel roofing even comes with 45 or 50 year warranties which is impressive. But the sheet-metal itself is just one part of the roof and even if, for arguments sake, they were to last 50 years, the longevity of the roof depends on the behavior of all the other roof elements.

The roof is subjected to some of the fiercest forces of nature – moisture, temperature, wind, etc. Assuming it is installed well (won’t blow off in the wind) and is properly insulated against moisture (won’t let moisture in and won’t trap moisture between its layers) it is left to the attacks of temperature. Here in Romania that includes a very hot summer and a freezing cold winter but most importantly it includes drastic temperature variations over a short period of time. Hot summer days can be followed by cool nights and both fall and spring bring intense freeze-thaw cycles.

Even though the sheet metal may be able to withstand these changes and variations it does not isolate the inner roof layers from them. What more, it may actually amplify them – it will reach much higher temperatures then the ambient air temperature in the summer and will freeze very fast in the winter and it will conduct those amplified variations to the roof layers beneath it. These layers will decay BECAUSE of the behavior of the metal roofing.

The metal roofing may last a long time but may contribute to destruction of the roof many times during its lifespan. A roof that needs to be fixed every 5 or 10 years is, in my mind, a failed roof. Or, put another way, I aspire for a roof I can forget about for the rest of my life.

Insulation

The second most important function of a roof is insulation. Since warm air rises from below (inside the house) and falls from above (outside the house) the roof is the most vulnerable escape of heat.

This insulation can be achieved by:

Brute force – industrial insulation solutions – such as the insulation suggested and often used in Earthships.
Natural Materials – materials such as sheep’s wool or hemp can be used as insulation when properly prepared/treated.
Nature itself – a living roof offers (in our climate) three important layers of insulation: earth, plants and snow.

Of the three options I trust nature more then the others because it is a dynamic system that adapts to climate conditions:

Earth – though it is a poor insulator it has good thermal mass. As such, it absorbs ambient changes and dampens the effects of those changes from the layers underneath. In the summer it heats slowly and depending on its depth will usually stay much cooler then the ambient temperature. In the winter, it again accumulates “coolth” before passing it through to the lower layers.
Plants – in the summer, plants (assuming they have enough water) provide cooling – through transpiration – release of moisture to the air (sweating). In the winter they die back into a naturally insulating later. That layer will decay in the next spring/summer and nourish new growth.
Snow – is actually an excellent insulating layer (insulation is typically created by materials that have pockets of air). The combined effect of snow, on top of dead plants on top of earth provides substantial insulation for the under-layers of the roof. In contrast, Earthships include a hot water system to melt snow and ice to harvest water – that generates water at the expense of insulation.

All this boils down to the one most important feature our architect pointed out when he introduced us to living roofs. A roof with an outer layer that absorbs climatic shifts and creates relative stability for the under-layers.

Water

Our main source of water is a well with a surface pump. However I do believe that water may potentially be a challenge in the future (I am thinking on a scale of 20+ years). I would love to be able to incorporate an independent water supply such as rainwater harvesting can provide BUT:

The entire system (roof + drains + cisterns + filtering) is a very expensive part of an Earthship build. Since we are trying to create an Earthship that we CAN afford to build – letting this system go is very tempting.
Harvesting rainwater while compromising and/or complicating the two core roof functions of shelter (see longevity) and insulation doesn’t make much sense and is not very appealing.
I believe the best (and surely more affordable) way to filter water is through the ground itself (though we do have to deal with hard water issues).
I believe that the best (and surely more affordable) place to store water is in underground aquifers and not in plastic containers.
The way we, as humanity, are treating the atmosphere worries me to the point that I am not convinced rainwater can be a reliable long term source of water.
I have doubts about the quality of rainwater as drinking water (the quality of the water is effected by all the materials the water meets on its way to the cup and can change its characteristics when stored over time).
Our vision for our home goes beyond our house and we hope to create an ecosystem where more water is retained in the earth.
We have drastically lowered our water consumption and continue to be very vigilant about it.
We intend to build an outside shower for the warmer months of the year which will include rainwater harvesting and solar heating – so that too will reduce the “water load” in the house itself.

Rainwater harvesting from the roof simply doesn’t appeal to us. The lower cost, simplicity (though it needs to be done right to work) longevity and insulation performance of a living roof make it a more appealing solution.

We are considering some kind of cistern (1000-2000 liters) to both improve electric efficiency and if we manage to incorporate the cistern indoors and near the front glazing we may be able to bring up its temperature before it goes into the water heating system.

Structure

An extra bonus is that the structural strength of rammed tires seems superbly matched for the load requirements introduced by a living roof. The original combination of all-tire U’s and east-west orientation of root rafters make for an out-of-the-box-ready structural solution for a living roof.

I am assuming that we will need an additional structural face element to support the weight of the living roof above the greenhouse and corridor. I am thinking that beautiful natural wood posts will do the trick. And, ironically, to keep it simple, we may also embrace the raised front lip design of the original Earthships.

Construction Earthship Uncategorized

What is different about “Global Model” Earthships?

Post author By iamronen
Post date December 1, 2011
8 Comments on 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:

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.
Less Work – rammed tires are hard work much more difficult then concrete-can walls. They take longer to build (given the same manpower).
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.
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:

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).
More Concrete – much more concrete is now used in the project – both in the buttresses and in the internal walls.
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:

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).
Humidity – increased humidity in the greenhouse can be vented out through its skylights without automatically effecting the living space.
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:

More construction – a new wall requiring footings and framing has been introduced.
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 🙂

Construction Earthship Hemp Uncategorized

From Hemp to Earthships

I believe and have passionately shared my belief that hemp-lime construction is one of the best methods of construction available today (at least in the Romanian climate in which we live). We were planning to build with hemp-lime and our architect designed a magnificent house for us – unfortunately we could not afford to build the house so the project stopped and we are living in the slightly renovated traditional Romanian house on our property.

Hemp Difficulties

Building with Hemp was going to be an uphill effort. It was difficult to source materials (we finally found some hemp in neighboring Hungary) and natural hydraulic lime (NHL) is also a rarity here (we found it imported from Italy and Germany). It also seems we would have had quite a challenge mixing the hemp-lime mortar since the best suited tool (pan mixers) are not to be found here. We also had a relatively short window-of-opportunity to build since hemp-lime needs to set (~8 weeks) before the first frost appears – and it arrives early here. So despite our passion and investment in hemp we can say in retrospect that there were many cues pointing us away from it.

Foundations

When we realized that there wasn’t enough money to build the designed house we started looking at ways to scale down and simplify the house so that we could build it. One of the things we explored were the foundations. Though we had relatively cheap foundations they were still a major expense in the project.

Our house is to be built on a gentle south-facing slope and the plan was to excavate so that the back of the house the excavation was about 1 meter deep. Then we would fill the entire surface with rocks – starting with large rocks (~40cm) and then adding layers of smaller and smaller rocks until we arrive at gravel and sand. On top of that there would be a concrete slab which we preferred to avoid but was required due to the green-roof planned for the house.

With these foundations planned and in mind I first came (about a month or two ago) across two new (to me) themes: rammed-tire construction & underground houses.

Rammed tires is a method of construction where used car-tires (abundantly available is modern garbage) are packed full of dirt and stacked to create a thick monolithic wall that is its own foundations. These need to be built on undisturbed soil and no additional foundations are required. Inside they are finished with earth.

Underground houses (though they may conjure up uninviting images of war shelters) is an approach to building houses that are to some degree (many options here) surrounded by earth. Though there are numerous advantages to this the one that stands out in my mind (as we are living in a small and inefficient house that consumes loads of firewood and the work involved in it) is energy efficiency. Regardless of how you deal with the house fabric (insulation, thermal mass, etc.) when you build a house above ground and its freezing outside then you need to deal with subzero-temperatures surrounding the fabric of the house. When you build a house underground and its freezing outside then you are dealing with a relatively warmer (~10 degrees Celsius) and steady (a couple of days ago I witnessed an almost 20 degree Celsius shift in 4 or 5 hours!) surrounding. In the summer when its hot outside the earth is relatively cool so that works for you too.

So, with that in mind, I’d like to qualify my initial statement in that hemp-lime construction is one of the best methods of construction available today IF YOU ARE BUILDING ABOVE GROUND.

Earthships

You can’t get far reading about rammed tires without coming across Eartships. An Earthship is a concept developed (if I am not mistaken – way back in the 70’s) by Michael Reynolds – an American architect. His vision is to create an autonomous house generating its own electricity (solar/wind) and water (rain run-off collected from the roof) all built with waste materials that mankind has generated in abundance (tires, beer-cans, wine bottles, etc.).

Ironically my first (and still leading) impression is that it is an impressive vision (amazingly elaborate and thorough) but also one that is anchored in the indulgent and abundant USA mentality (a recurring symptom in most of the “green” construction methods I have come across). Though Earthships are designed to be owner built they are still very expensive and a far cry from becoming something anyone on the planet can afford to live in.

We could not afford to build an Earthship based on the template described by Michal Reynolds and we are very well off compared to the general population of Romanian villages. So bringing Earthships into our context is quite a challenge.

Gradual Self Build

There are numerous benefits to Earthship construction compared to hemp-lime construction and though I will mention some of them there is one that outshines all of the others.

Earthships are designed to be owner built and indeed my searching and reading online seems to indicate that Earthship is one of the most popular self-build techniques for non-professional builders.

But in addition to being suitable for owner-built houses, Earthships can be built gradually. With relatively low costs we can start next year to pound tires that will make up the shell of our house. It may 2 or 3 years (unless we get help) but we can start and as we do that we can continue to develop our income stream and as funds become available invest more and more in the construction. Given that we have a temporary house to live in there is no need to wait, no rush and no pressure at all.

Earthship – Hemp Comparison

Beyond self build there are numerous points of comparison I’d like to make a note of in comparing hemp-lime build to an Earthship-like build. It should be said that what follows are things that matter to us including choices we may make that are not directly true to the core Earthship concept.

Feature	Hemp	Earthship
Foundations	Like all natural fiber based walls hemp needs to be lifted above ground level so that it does not come in contact with water that may drain past the building. In our case the green roof required a foundation that could carry and distribute the load of a roof structure, earth, plants and snow.	No foundation is required. The walls themselves are a foundational structure. The tires, when rammed with earth way over 120kg each (they have to be packed in place because they cannot be moved). In addition the tire walls are either completely immersed or bermed with earth which adds additional support (and load on the walls!).
Floors	Both building systems can incorporate a variety of floor systems. In both cases, in our climate, there needs to be good thermal insulation (our floors can get to be very cold) and good vapor barriers
Walls	Hemp-lime is a non-structural material which means that it is not load bearing. Therefore hemp-lime walls are an infill for wood framing (usually either stick framing or post and beam). There is also need for shuttering (during construction) into which the hemp-lime mortar is cast.	Used tires pile up as garbage almost everywhere in the world – so besides the effort of finding it, sorting through it and transporting the tires to your build site there are no additional costs. It’s as simple as laying them on the ground and then the (very) laborious of pounding them with dirt. As we are not in a rush … we don’t mind taking the time to pound tires.
Finishing	Hemp-lime walls are porous and therefore breathable walls so they require a breathable finishing (usually lime-based). On the outside, regardless of finishing, the walls need to be protected with generous eaves.	On the inside tire walls are finished using natural earth finishes they I am assuming that lime can be used as well. This finishing is actually more critical in tire walls because the wall itself is not porous or breathable – so the finishing layer needs to be (for humidity responsiveness). The finishing is a pretty thick layers because first the gaps between the tires need to be filled to achieve a smooth surface – and only then can actual finishing layers be added. As for the outside there is no finishing issue since the walls are either buried or bermed (there is however an insulation issue – see below)
Doors	Our hemp house had quite a few doors designed into it. In that sense it was a typical house.	The original Earthships were, except of course for the entry to the house, without internal doors. They have evolved to the point where more elaborate internal design can lead to doors – so I’d say it’s pretty much the same as a regular house (although there is the option to build with much less doors.)
Windows	Windows in an above ground house are a pain. They are expensive (if you want good windows). They need to be installed with careful flashing to avoid leaks of water into the house. They need to be constructed and installed with precision so that they are also air-tight. In a do-it-yourself build they can be quite troublesome.	Earthships have no side windows – all the glass is in the front wall which is all glass – it is a relatively expensive element that requires basic wood framing, double-pane glass and very good flashing. The more modern Earthships actually have two glass walls – one is the outer wall which delineates the greenhouse and corridor to rooms; the other is the internal wall which encloses the rooms which is also mostly glass because we want as much sunlight to penetrate into the rooms. I have a feeling that the Earthship is somewhat simpler in this sense then a regular house – though I think the costs maybe similar if not higher. Earthships also incorporate skylights primarily as a ventilation but also as a light source. This is something that can be self-built so the expense can potentially be somewhat reduced compared to ready made skylights.
Insulation	Hemp walls need no insulation – they behave wonderfully both in terms of thermal mass and insulation. They do, as mentioned above, need to protected from moisture on the outside – wet walls are not good insulators.	Originally Earthships were built without insulation under the working assumption that they should interact with the earth itself. The modern evolution of Earthships in cold climates (where the earth, though warmer then the air, is still colder then a comfortable living temperature and could therefore suck heat out of the house) include insulation – usually rigid foam insulation (not very ecological) that is installed at a distance of about 1 meter from the wall itself (the space between the insulation is filled with earth).
Roof	Hemp homes can be built with almost any roof system. We were planning to build a green roof. Insulation is required and again can take on many forms.	Standard Earthship roofs are designed with a primary function (besides shelter of course) of rainwater harvesting. Here too insulation is a must and can take on numerous forms though standard Earthships use rigid foam insulation. We are currently leaning toward a green roof. This will deserve a dedicated post so stay tuned 🙂
Space Heating	Hemp homes can be very energy efficient if they are built properly which includes: airtightness, ventilation, passive solar, etc. But my intuition tells me that they still require heating which is can be a very challenging and complicated and expensive issue. Still they are above ground houses and need to cope with the dynamics outside environment (though the hemp walls, being constantly dry, tend to this very well compared to other wall systems).	Earthship heating requirements are probably much lower even then that of Hemp: Air-tightness is almost a natural consequence of burying your house in the ground … only the front wall deals with air leaks. Though these air leaks are not very critical because (a) the front face is a greenhouse which gets very warm (when the sun is out); (b) needs ventilation; and (c) is separated from the living area by another wall system. The house itself is embedded in a drastically warmer temperature – that of the earth (at coldest freezing), then houses above ground level (at coldest subzero temperatures). The entire south face of the house is a glass wall which utilizes passive solar to the maximum A basic Earthship is designed so that the house is not deeper then one room – so most of the space directly benefits from solar energy. The earth has inherently vast thermal mass because of its (a) thick earth rammed walls; (b) an additional 1 meter thick earth mass; (c) a layer of insulation; (d) the rest of the earth acting as a relatively stable thermal mass. The internal walls, earth wall finishes and potentially earthen floor also add valuable thermal mass which can store heat and gradually release it back into the space.

Joy

We are continuing to study and investigate Earthships and how they can apply to us. It feels promising.

We have been blessed with a temporary house in which we can live yet it is not a house which can become a house that supports and embraces us. This house is a wonderful shelter which can make building our new house a pleasant and healthy process.

The thought that we can begin a building process next year from mostly salvaged materials and then gradually move on with construction as work progresses and more money becomes available … and maybe move into a wonderful and pleasant house in 3 or 4 years is … joyful!