Is It Possible to Build an Earthship in Moist, Freezing, Expansive Clay Soil?

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.

How to Avoid Spacer Blocks in Earthship Tire Walls

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.

 

 

Earthships and Indoor Solar Systems

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?

 

Water – Pumping

The best and probably most comfortable and sustainable water pumping solution is gravity – but that works only if you have a properly situated source on your property (a spring at an altitude high enough to provide water pressure). We didn’t have it this good but we had a well and we had to install some kind of pump to get water flowing from it to the house.

Our research led us to two kinds of pumps – surface pumps and submersible pumps. We chose a surface pump (see why below). I am not an expert on pumps but here are a few things we were able to pick up along the way.

Water Pressure

Submersible pumps seem to be able to provide a higher water pressure then surface pumps. They use different mechanical configurations to pump water which effects water pressure. This is in addition to a rule-of-thumb that says that the closer the pump is to the source of water the higher the pressure it can provide. Though we installed our surface pump close to the well, a submersible (immersed in the water) pump is closer to the water source then a surface pump.

Installation

A submersible pump should be easier to install then a surface pump – but we haven’t done this so we can’t vouch for it. A submersible pump is, supposedly, simply lowered into the well where its weight stabilizes it in the water. This of course assumes you have a well deep enough (during all seasons of the year!) to accommodate the pump.

A surface pump is more tricky to install. Assuming you want to have it close to the well you will need to make a space for it. As we live in a climate with a freezing cold winter this meant creating an underground chamber that drops below the freezing depth (more on this in the next post in the series).

Overall Water System

A submersible pump is usually part of a system where a large water tank is installed in or near the house and fed directly from the pump. Inside the tank is a water level sensor that, when the water drops to a set level, activates the pump until the tank is full again. A second pump is then installed to feed and pressurize the water from the tank into the house. This way the well-pump doesn’t need to come on whenever you open a water faucet. The water is taken from the large storage tank (which, if placed inside, can also double as a preheating tank bringing the water in it slowly up to room temperature). The pump only comes on when the tank needs filling. This prolongs the life of the pump.

A surface pump provides a more or less consistent water pressure (usually assisted by a pressurized expansion tank). It comes on when water is required and shuts off when the flow stops. You can then direct and split the water flow as needed (keeping in mind the overall pressure that the pump can supply).

Local Wisdom

Local wisdom indicates that surface pumps are better – this is what almost everyone here uses. It is rumored (meaning that I haven’t confirmed this myself) that submersible pumps are more prone to problems and more sensitive to fluctuation of water levels. Professional wisdom (at least that we’ve had access to) seems to indicate that submersible pumps are better as they provide better water pressure and are more reliable then surface pumps.

Price

Good submersible pumps (in Romania) are much more expensive (our research has shown them to be at least 4 times more expensive then the ubiquitous surface pumps) than good surface pumps. Both come with a limited 2 year guarantee.

Our Choice

We chose to go with a surface pump for numerous reasons:

  • Price was high up on our list of priorities. A submersible pump (let alone the entire system around it) was beyond our means.
  • Almost anyone we spoke to (in our village and others) who has a pump uses a surface pump and claims it is reliable.
  • Almost anyone we spoke to (in our village and others) said that submersible pumps are problematic unless they are installed in optimum conditions (we don’t know what these conditions are).
  • We needed a diversified water supply – 2 structures + 2 outside locations (making it difficult to include a water storage tank to supply all our needs).
  •  We did not have a winter-proof place to install the water tank needed for the submersible pump (creating one would have been complicated and expensive).
  • We preferred to start with a system we can scale up if needed rather then start with a scaled up system.

There are numerous brands of pumps available in Romania. Many of which are very cheap – we tend to avoid these. Then there are some very expensive brands (both submersible and surface). We chose to go with a reasonably mid-priced German brand – Grundfos. We hope this proves to be a good choice (reliable performance for many years). So far so good.

 

 

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:

  1. Brute force – industrial insulation solutions – such as the insulation suggested and often used in Earthships.
  2. Natural Materials – materials such as sheep’s wool or hemp can be used as insulation when properly prepared/treated.
  3. 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:

  1. 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.
  2. 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.
  3. 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:

  1. 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.
  2. 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.
  3. 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).
  4. I believe that the best (and surely more affordable) place to store water is in underground aquifers and not in plastic containers.
  5. 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.
  6. 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).
  7. Our vision for our home goes beyond our house and we hope to create an ecosystem where more water is retained in the earth.
  8. We have drastically lowered our water consumption and continue to be very vigilant about it.
  9. 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.