Category: Earthship

That title isn’t quite fair because it isn’t exactly true. But given the hype around Earthships I felt it is a deserved.

This short post was prompted by a longer article where the author inquires into the performance of Earthships in Europe. He raises exactly the same questions I encountered in my research. He made an effort to reach out to known Earthship projects in Europe to inquire about their performance and this is what I read between the lines:

• There are very few Earthships in Europe.
• Most European Earthships do not have permanent residents (if at all, cats do not count).
• There is very little information on performance.
• From what little information there is, it seems there are severe performance issues.
• There is very little sense of joy from all this.

The author is less blunt then me. I’ve written before that I think the Earthship “formula” is wrong for a cold and moist European climate. I also feel that the knowledge around Earthships is incomplete because I did not come across any information on why they are designed they way they are,why they work where they do and why they do not work in the European climate.

I did however find the Passive Annual Heat Storage book where (1) I finally found explanations on how underground houses behave and (b) answers to all the questions presented in the linked article and then some.

Dan contacted me and sent me this video of an Earthship built in Australia. The video includes image sequences that are packed with information. If I find any more information on this build with still pictures and words I will update this post with it.

One of our core projects here at Bhudeva is building our future house. We have been doing a lot of research on sustainable and ecological construction and we have been facing many challenges in bringing existing knowledge into context for our life here in Romania. Our latest design envisions a mostly underground house that will provide us with a year-long steady temperature of 21c without any energy inputs (neither for cooling in the summer nor for heating in winter). The core of our design is based on the concept of Earthships. At the heart of Earthship construction are massive walls built of tires that are packed full of earth.

So for many months we’ve been looking and asking around about tires here in Romania and this is what we found out:

• Most tire dealers and repair shops sell some used tires that barely have treads but can still just barely be driven for 15-20 ron a tire (just to be clear – they are sold to people with old cars who can’t afford new tires).
• Tire dealers are required to “recycly” through the state (represented by licensed operators) a certain amount of tires to offset new tires that they import.
• The dealers are paid a symbolic 50 ban per tire collected from them.
• Most of the collected tires are then sold off to different uses . Some are recycled (yey!!) into products such as car mats … however …
• Many (we suspect most) are sold at a premium of 10-20 ron per tire (purchased in quantities of tens of thousands) to cement manufacturing companies (and their likes) who use them as fuel (boo!!) – it seems that a single tire contains a equivalent of 7.5 liters of oil!
• We know of at least one giant pile of tires in Cluj-Napoca that is just sitting there slowly decomposing in the sun. We assume that other such piles can be found all over Romania.

Used tires is a waste product we (especially those of us who drive cars) are all responsible for creating. The concept of Earthships (built with earth-packed tires) was born out of recognition that this huge source of waste (available all over the planet) can be put to good use in creating houses (which it would seem are also needed all over the planet). Any recycling of tires requires high energy inputs (often starting with shredding). The thought of all the toxicity released when tires are burned as fuel (a single tire contains a equivalent of 7.5 liters of oil!) is mind-boggling. When used to build Earthships the tires are used as is and because they are completely buried they do not decompose or release any toxic gases (which they do when exposed to the sun).

Whenever we speak to someone in Romania about needing tires we quickly encounter an opportunistic greed. Regardless of the “asking-price-per-tire” we would also need to find a solution to sort through tires and have them brought over to our place which incur additional expenses. All this caused us to rethink about construction with tires – suddenly it seemed that concrete blocks that easily snap together would be much cheaper (and way faster to build with) then working with tires. However we really don’t want to resort to massive construction with concrete … so we scratched our heads and though of you … yes you 🙂

Inspired by the awesome waves of goodness we encountered with the introduction of Cutia Taranului we decided to once again try collaborating with you – our fellow Romanians. Also in the spirit of Cutia Taranului we realized that the best way to get tires would be to go around the existing system rather than through it. It boils down to this … the next time you buy tires we would like to ask that you keep your old tires, don’t leave them to be used opportunistically as fuel.

Now look at your old tires … what do you see? Look closely … you are holding a personal invitation to visit with us at Bhudeva including at least a pleasant conversation, a tour and a tasty cup of herbal tea … and best of all you have become a contributer to a unique experiment in sustainable construction taking place here in Romania.

For our house we are going to need about 2000 tires (though we have other structures planned … so we will try to collect much more). Tires come in different sizes which are indicated with a combination of numbers printed on them. All you need to look at is the first number – the one that has the letter “R” in front of it. We need tires that are labeled as either “R15” or “R16′”. The larger “R16” tires will be used for the base of our walls and the “R15” tires will be used on top of them for most of the wall.

Lastly … since we are talking about garbage 🙂  We are also going to need empty cans, empty wine bottles and used cardboard boxes. So if you are already holding on to tires an invitation to visit Bhudeva then please  hang on to these things you may be tempted to throw out 🙂

Since tires are not often changed this initiative may move a bit slow so … please do spread the word to your family and friends 🙂

 

Ventilation and air quality is one of the last and most problematic issues I’m left with in regard to Earthships in cold climates. Cold climate is what I’ve experienced in a mild Romanian winter which includes snow cover, continuous (many weeks if not months) subzero temperatures and no sunshine (passive solar gain) for two week stretches.

To avoid confusion (as I have encountered it myself in trying to figure out this issue) let me re-iterate: the problem I am trying to outline here is not heat but ventilation – the removal of stale air and it’s replacement with fresh air. There is no question in my mind that no matter how efficient a properly insulated Earthship can be, in our Romanian climate, it will require additional heating. However heat and it’s origin does effect the flow of air throughout the house.

In this post I will try to outline what I’ve been able to figure out so far. The bottom line will be that in cold climates there is a ventilation problem. I hope this post provokes further input and conversation through comments. I would especially love to hear from people who have lived in Earthships in cold climates and their experience of ventilation and air-quality. Then, in a separate follow-up post I will try to present what seems to me like a potential passive, energy efficient ventilation solution.

Classic Earthship

The classic Earthship ventilation theory is simple and straightforward. Fresh cool air enters from the operable windows on the front face. This air is heated by solar gain, warm air rises and escapes from the skylight resulting in a continuous flow of fresh air through the living space.

The ventilation problem is already present in this simple model. What happens when it’s so cold that operables and skylights (both covered by snow) are kept close to keep heat in (and snow out). To my understanding there is no air flow.

 The only way to get fresh air in and stale air out is to let the cold in. Earthship theory would say that is not a problem because the thermal mass of the house contains enough warmth to compensate for coolth that comes in through the openings. In our climate I don’t think will hold true. I think we will have to heat the house in addition to water solar gain (hopefully much less then a house built above ground) and ventilating would entail precious heat loss.

Global Model Earthships

The Global Modal Earthships make two distinct changes to the elements of ventilation (actually there is a 3rd which I will address separately, see earth-tubes below). The first is the introduction of the corridor wall which separates the living spaces from the greenhouse. The second is the skylight over the greenhouse which comes INSTEAD of a skylight in each living space (I wasn’t sure about this until I encountered this video from Earthship Biotecture). In this configuration the greenhouse has been described as an air-lock that supposedly provides better climatic control by isolating and containing variations between it and the living space.

 There are now two ventilation circuits in the house. The first is between the outside and the greenhouse and the second between the greenhouse and the living spaces. The ventilation loop between the outside and the greenhouse is obvious and is similar to the classic Earthship approach.

I have some doubts how well the ventilation loop between the greenhouse and living space will work. As I understand it, if passive solar gain is the main source of heat then the greenhouse will always be warmer then the living space. This means that there may not be much flow from within the living space (cooler and heavier air) to the greenhouse (the already warmer and lighter air). It seems to me that the flow in the greenhouse may over-power the flow from within the room. This may be effected/controlled by alternating openings (eg: first ventilating the greenhouse, then closing it and ventilating the living spaces) and height positioning of the ventilation passages between the corridor and living spaces.

As with the classic greenhouse I do not see any potential for passive ventilation on cold cloudy winter days.

When a source of heat is added inside the living space and the hot inside it becomes warmer then the greenhouse – there can be a ventilating flow between the two spaces (and of course heat will be lost from the living space to the greenhouse).

If, in addition to the heat source, the front operables and skylight are opened then there may be some draw of fresh air from the greenhouse to the living space (and of course heat will be lost from the living space to the greenhouse and then quickly to the outside).

So, it seems that any ventilation will come at the expense of precious heat.

Earth-tubes

Global model Earthships introduce another element they call “Cooling Tubes”. These are tubes that are buried in the ground (~20 feet) behind the house and penetrate the rear wall.

They are intended to provide natural cooling. Warm air in the greenhouse is released through the skylight this creates a draw pulled in through the cooling-tubes. Warm air is drawn into the tubes from the outside, loses heat to the ground in which the tubes are buried and arrives cooler into the house.

This solution addresses ventilation in a hot climate, it does not address ventilation in a cold climate. However, I do believe it points in the right direction. More on that in an upcoming post.

We have beautiful, heavy, clay-rich soil. It’s great for cob (which explains the local proliferation of cob houses), great for earthen plasters and earthen floors but it seems to pose some challenges when it comes to underground construction such as Earthships. I hope in this post to outlines the challenges and what solutions I have come across to deal with if. If you’ve built in an Earthship with such soil then please stop by and share your experience with it. Midway into writing/editing this post I came across this thorough description of expansive soil and their potentially adverse effects on construction. From reading it and a few others resources I feel is it important to note that:

• Almost all mentions of expasive soil issues are in relation to foundations. An Earthship has no foundations.
• Almost all mentions of expensive soil relate to hard-concrete responding to intense uneven pressures. An Earthship is inherently a “softer” structure (then concrete) embedded in the earth. We intend to embrace that concept and even our floor will be a “soft” earthen floor and not a rigid concrete slab.
• Expansive soils are not inherently a problem – fluctuations in their moisture content is a big problem. If moisture content is stabilized then the problem is largely diminished.
• An Earthship is inherently a massive structure (even more so with a living roof we intend to add) and as such an Earthship is capable of “pushing back” against the forces of surrounding expansive soils.

In addition to all this we have had an opportunity to observe how things behave in real life which is an excellent teacher – especially as I am about to get into a lot of theoretical ideas. We live in a cob house that was built in 1934 and it is structurally sound. It has partial peripheral stone foundations and is holding up find sitting on expansive clay. Other houses in the village were built with without any foundations and have been standing for many years. Of course there are also decayed houses … but I cannot say what kind of role soil-expansion had to play in their history. Though they have not yet withstood the test of time, we have built two underground concrete boxes (with manhole access) for our water infrastructure. Their walls are ~10cm thick with rebar – and they have shown no signs of stress problems. We have had a few ditches open over recent months and they have seen many transitions from wet to dry and they also showed no structural decay.

Expansive Clay Soil

It took me time to understand what all the structural fuss and warnings are about “Expansive Clay Soil” and it all went back to understanding the structural qualities of the soil itself. The soil composition itself is considered clay-rich and my first misconception was that that meant it was mostly clay. This is incorrect … clay rich soil has a relatively small percentage of clay particles in it – typically ranging from 10% to 25%. While the clay is not a major quantitative element it is a dominant qualitative one.

Clay particles in clay-rich soil expand when they come in contact with water. As it absorbs water it becomes sealed and much less penetrable for water. This makes saturated clay-rich soil slow-percolating. We witnessed this clearly when we dug a small hole in the ground and filled it with water. The small pool stayed in place for quite some time, percolating into the ground very slowly.

This makes clay-soil a structural force to deal with when building an underground house. There are two phenomena that lend a hand to the expansive behavior of clay. The first was mentioned above – clay absorbs moisture and expands. So, for example, the fall season rains saturate the soil and the clay expands. Then winter brings into play the second phenomena – freezing. The saturated and already expanded clay soil is now exposed to freezing temperatures which cause even more expansion.

These forces are insignificant in a bucket of clay but can translate into potentially thousands of tons of force pushing up against a house that is buried in the ground. After carefully internalizing the “expansive” behavior of clay it seems to me that the problem is not the clay rich soil itself but it’s exposure to moisture.If it’s kept dry then clay rich soil is actually an excellent structural soil – it dries into a very solid earth – ideal for rammed earth tires … IF you keep it dry.

Implications for Earthships

I can identify numerous implications of working with/in rich-clay-soil when it comes to Earthships:

• Construction work – wet clay soil becomes a heavy muddy substance very difficult to get around in let alone to work with.
• Rammed Earth Tires – if a tire is packed with clay earth that is not dry (enough?) then when it will dry it out the earth in it will get compacted some more. That could be a structural nightmare.
• Drainage – clay rich soil has no drainage – it saturates with water and seals itself. Period. Though I haven’t seen this acknowledged in any written materials (off and online) my impression is that that is actually a welcome feature to one half of the water drainage problem of a house – surface water (once the soil is saturated) will simply flow away – so all you have to do is divert it to make sure it flows where you want it to go (preferably away from the house). The other half of the water drainage problem comes from below … and that problem isn’t unique to clay-rich-soil. It simply means that you need to have good drainage beneath the floor and around the house.
• Structural Pressure – now we that we have figured out that the earth around the house may be pushing up against the house with tremendous force – something needs to be done about it.
• Insulation – wet earth sucks warmth out of the house. The Earthship is bermed with earth all around and so to maintain energy efficiency any contact with wet earth must be avoided or mitigated.

Possible Solutions

Tire Walls Inherit Strength

In a typical underground house the forces of the soil would be acting directly on standard earth-proofed walls (usually concrete). The first main difference about Earthships is that the walls are massive … twice the width of typical walls. The tightly packed tires offer much more structural resistance then their counterpart typical walls. In addition we are planning to have the internal walls also be tire walls for additional mass and structural support.  In addition, outer Earthship tire walls are designed to lean back into the surrounding earth which offers even more lateral strength. 

Use Dry Clay Soil

This is easier said then done (at least in the Romanian climate which can rain any time and for any duration of time):

• The building site would have to be setup with a large area which is arranged to dry soil.
• This area would have to be sheltered from the rain.
• It would also need to have exposure to sun and open-air circulation to promote drying.
• It would need to have a large surface area so that a substantial quantity of soil can be dried sufficiently for use in both tires (slow and continuous consumption of soil over a long period of time) and backfilling (rapid consumption of soil in a very short period of time).

I suppose that if the excavated earth was placed in a narrow (north-south) and long (east-west) mound and that if that mound was covered with a slightly elevated clear plastic cover while enabling comfortable access for both wheelbarrows and a tractor – that soil could be reasonably dried!?

This also means that the tire walls themselves need to be kept dry throughout the project. Since Romanian weather includes rain-showers throughout most of the year (except of course in the subzero temperatures of winter) – this means that there need to be plenty of cover materials on site and a quick response when rain showers do appear.

Bring in Alternate Soil

Though it can become a substantial expense it is possible to bring in sandy, good draining soil for both ramming tired and backfilling. The supply of soil can be regulated as needed so it can be kept reasonably dry. Also, since it doesn’t suffer from expansion it would be OK to use it when moist knowing it will eventually dry out.

This is something I would prefer to avoid because (a) it is costly and (b) it goes against the core idea of using local materials for construction.

Backfilling

The design of the Global Model Earthship introduces a perimeter wall of insulation and moisture barrier set about 1 meter away from the outside of the tire walls. This creates two distinct backfill areas: (1) between the tire walls and the insulation; (2) outside the insulation and moisture barrier. The first backfill area between the tire wall and insulation/moisture barrier is a space that can and I believe should be completely covered by a moisture barrier. This means that this soil humidity is going to be relatively stable. If it is filled with mostly dry soil then it will also not change much, if it is filled with moist soil – then it may shrink as the envelope of the house dries over the first years of operation. Either way that part of the backfill is relatively stable and becomes and extends the fabric of the house. To my understanding it should absorb most of the additional pressures that come from the surrounding soil BECAUSE it isn’t structurally packed liked the tires – it is a more dynamic wall up against the more static tire-wall. Then there is the second – outer backfill – the one that is outside the moisture barrier. For this backfill I would prefer to use a good draining soil. It is a smaller volume of backfill and therefore less expensive to do so. It would serve two purposes. One is faster draining of any moisture that comes near the fabric of the house. The other is an additional pillow against the pressures of the surrounding earth. So already there is plenty of support against the potential pressure of the surrounding expansive clay soil.

Gravel

I am thinking of starting the build by placing (on the excavated undisturbed soil) ~30cm of gravel (with built in drainage – see below). My thoughts are to excavate in such a way that the resulting surface will be slightly downhill (more elevated towards the back of the house. A level layer of gravel would then be placed on it. The gravel would cover the entire construction area up to and including the perimeter insulation wall and future tire walls (which will be built on the layer of gravel).

Common sense tells me that the gravel layer may also act as a flexible absorption layer should their be any excess pressure due to expansive soil from below.

Drainage

On the gravel I would place a french-drain system made up of:

1. A perimeter drain pipe.
2. An inverted U drain pipe in every U module – with a T joint which leads out of the U and into the greenhouse/corridor (I feel it is better to avoid running any pipes under the tire walls). The  corridor connections would need to eventually pass through the stem wall of the inner corridor wall.
3. Two main main drain pipes which collect flow from the U-drains and lead out to the two sides of the house and connect to the perimeter drain.

This would both remove excess moisture should it ever accumulate and create (as our architect suggested) a pleasant and mud-free work zone.

Living Roof

Our intentions are to install a living roof instead of a rain-collecting roof. The weight of the living roof as carried by the all the (inner and outer) structural tire walls is an additional counterweight to pressures from the surround soils. Most of the weight of the roof will be transferred down into the ground below the house. Some of the weight will be transferred to the side walls to do their outward leaning angle. This is unexpected and welcome benefit of the living roof.

Moisture Barriers

Moisture barriers are, I believe, a given in Earthship design (and any other well designed overground/underground house). Though in an Earthship I believe there are two aspects to this challenge. One is during construction (which in a self-build can take years) and the other is the typical finished house. My thinking is to start with the moisture barrier from within the tire walls – so it would be placed on top of the gravel. I think that a 4 meter wide would sheet would be enough to go from within the wall, underneath the tires & the the inner backfill and over the top of the first layer of insulation panels. Then each course of insulation would be covered by another overlapping sheet. In the end a top sheet of moisture barrier will extend from the roof and will overlap the top course of insulation sheathing. During construction a temporary cover will be needed to cover the breadth of the tire-walls + infill area + insulation panels. The floor area can remain uncovered as rain water will be diverted by the drains.

Insulation

Though insulation is not directly related to the structural aspects of expansive soils it can effect the thermal performance of the house within these soils. Expansive soils hold a lot of moisture content and wet-earth can suck warmth from a house much more then dry earth.

Thorough insulation (as would be required in the Romanian climate), in my opinion, has not yet been achieved in Earthship designs (based on freely available information online). This is a testament to the fact that Earthships do not originate in cold and soggy climates and soils. Insulation was added in later Earthship designs and is now standard in the Global Model, but I believe it is still not up to the task of dealing efficiently with the Romanian climate. First, as designed in the Global Model, the insulation panels are better off protected from moisture – so it is sensible to install them within the moisture barrier sheath. In addition to that I would like to extend the insulation to close off additional energy bleeds from the house:

• Floor insulation will be added throughout the house – above the gravel drainage layer and beneath the earth floor.
• Floor insulation will also extend beneath the tire walls – it will be laid out around the perimeter and beneath the inside walls before tires are put in place and filled with dirt.
• Floor insulation will also extend beneath the inner backfill area and through to the perimeter insulation panels.
• The stem-wall for the inner corridor wall will also be insulated beneath ground level with R5 insulation panels to prevent energy bleed through the concrete.
• Similarly the concrete footers for the front wall (living roof load bearing) posts will be insulated below ground.
• Roof insulation will continue and meet the perimeter insulation panels using R10 panels (this insulation is closer to ground-level and therefore exposed to more sever ground-frost).
• On the front face wall frost-blocking (45 degrees) insulation panels will be installed.

I am still debating what to do with the planters. I believe that the presence of composting soil and living plants and solar gain makes adding ground insulation in the planters redundant … we’ll see. Together with the bermed earth and living roof this should provide an effective shell of insulation that should prevent energy bleeds from the core of the house to the surrounding earth.

Summary

It seems to me that if properly dried soil (still no clear idea on how to achieve this) can be created and maintained on the work site, together with uncompromising moisture barriers and insulation should make it OK to build an Earthship in clay soils. I would be grateful to hear other opinions and other experience on this issue.

I came across these two excellent illustrations of how spacer-blocks can be almost completely avoided in rammed-tire walls. It’s one of those cool smart and simple things. It comes complement of Earthship Belgium from an excellent post on how to efficiently organize and build rammed-tire walls.

Both of these solutions rely on the use of one-tire size throughout the project. The idea is to make the corner out of a tire who’s center is aligned with the faces of the two tire walls. Though the image display a 90 degree corner I believe that the same idea would work for any angle.

The same principle can be  used for T or Y junctions of two U modules. In this case two tires are used to create one level of the Y and a larger diameter tire is used to overlap the three tires below.

This takes care of everything except end-blocks (which you will inevitable get if you use tire walls for the inside walls as well). Earthship Belgium provide another article  about spacer-blocks – at the end of which you will find an explanation on how to create half-tires. I have encountered half-tires in my online searches before and though it is an appealing solution (no cement on site until later in the project) – it seems to me that cutting tired can be difficult unless you have the right tools for it.

I came across a lot of online hints that spacer blocks could be avoided (less concrete and much less hassle) but I couldn’t find a clear explanation of how this is achieved. Now I know … and now you do too. Thank you so much Willy and friends at Earthship Belgium.

 

 

It seems that Earthship Biotecture have put together a wonderful animation of how a “Global Model” Earthship is built. It is beautifully executed, very educational (many subtle details) and answered a few questions I still carried with me.

Solar systems such as hot-water heaters and solar-electric panels are an almost obvious component of any Earthship. These are systems we would love to embrace but simply cannot afford to buy given their market prices. However, we can and intend to go about building our own. We have been researching do-it-yourself systems for quite some time and we have viable options.

My point in this post is not to go into detail about do-it-yourself solar projects. If you are interested in these things then I strongly recommend you bookmark and spend time at BuildItSolar which overflows with DIT solar projects. My objective is to suggest, in regard to solar hot water and electric photo-voltaic panels, an interesting potential feature for do-it-yourself-ers in an Earthship – bringing the systems indoors. This is something that would be more difficult to achieve with off-the-shelf systems which come in standard sizes, but self-builders can create panels in practically any size.

In an Earthship these systems are typically installed either on the roof or on, in “Global Model” Earthships what appears to be a dedicated and sloped (optimized for solar gain?) surface on the front face of the house.

Photo-Voltaic Panels

One of the greatest challenges when it comes to building your own panels is weather-proofing. The frame itself, glazing, insulation materials … all have to be weatherproof. In addition the electronics need to be properly insulated from moisture.

Bringing the panels indoors makes all these problems go away. I am thinking that if the glazing is extended all the way up with continuous wood-framing it should be pretty convenient to install panels inside.

The DIY panels can be sized to practically any size. We are planning an Earthship with a front face of over 20 meters long, so a 50cm high strip of panels allows for almost 10sqm of safe and protected solar panels.

Solar Hot Water Panels

A solar hot water system is slightly more complicated since it involves other elements depending on the overall system configuration (boilers, storage tanks, heat exchangers, etc.). Though I will focus on the solar panels themselves I believe that bringing these panels indoors may potentially simplify the overall system.

In Earthships Vol.III Michael Reynolds introduces Mechanical U’s (“U” shaped spaces are the basic building block of an Earthship). These are U spaces which are used for functions that do not necessarily need direct solar gain (such a laundry, storage spaces, etc.). I am thinking of incorporating a Mechanical U with sloped glazing (continuous with the rest of the front face of the house) and to use that glazing as a space for installing the solar panels.

 

This of course solves the basic weather proofing issues shared with the electric panels. But I believe there may be a huge extra benefit – I wonder if having the hot water panels inside the greenhouse/corridor space solves the problem of water freezing in the pipes. I don’t know if this will actually work, but if it will, it can tremendously simplify the system. If freezing is no longer a problem then the hot-water panels can be connected directly to the hot water storage tank without any need for antifreeze (a liquid that prevents the water in the pipes from freezing) & heat exchange mechanism or drain-back solutions (that empty the water pipes in the solar panels to keep them from freezing).

In both cases placement of the systems indoors reduces the need to penetrate the outer fabric of the house for pipes and cables and also makes the panels theft-proof  (I’ve come incidentally across two reports of stolen solar panels from Earthship roofs!). In both cases it is not possible to optimize the direction of the panels as the seasons change, however a winter-optimized angle of the glazing inherently comes with an added benefit of some degree of protection from over-heating (by not facing the sun directly).

It seems to me that DIY indoors solar panels are in alignment with Earthships which are designed to be owner built. It seems that doing so comes with both huge financial savings and added-functional-value and simplicity. Too good to be true?