Monday - January 30, 2012

Freezing temperatures have arrived together with clear blue skies and a white blanketed earth. I took a walk up the hill today with Loui (who is still not completely at peace with a leash):

and this is what we saw

How to Pile Hay?

The other day Andreea decided to clean out the barn where we currently house our flock. She had setup it up with areas covered with hay which the flock really liked. Over time the hay accumulates moisture, droppings and food scraps and had become … less attractive. So she pulled it all out and dumped it outside (which turned into a magical playground for the flock who explored the hay as if it was heaven). Then she went to bring new hay from one of our piles … and then called for help.

The hay piles had accumulated a substantial snow cover. One of the piles, the one we made and also the one closest to the barn, was not arranged very well so that moisture (and now frost) had found its way deeper into it then the other piles. So it was much harder work then we thought it would be. We managed to get the barn re-done and I began to appreciate the skill that goes into properly arranging a pile of hay in such a way that it will hold, be protected from the weather, and comfortable to take apart. I still don’t know how to do this … and this post will not provide a thorough answer. However …

I then sat at the computer and decided to search for some information on this. The search results were astonishing:

  • First there was a generic and superficial article about hay at Wikipedia.
  • Then there was an article about how to stack bales of hay (which needs to be done properly so that the stacks do not collapse).
  • Then there was information (articles and videos mind you) about how to stack hay in Farmville (an online game).

Only after digging deeper into the search results did I find a photo-blog of someone who documented travels in Romania giving some information about how peasants make a haystack and how they take it apart. There is much more to it the these pages show … or should I say endless more details that are hard to describe unless you actually do it

The world has changed, and though I believe overall it has done so for the better, there a few weeds I would definitely pull out of the ground. Precious (as in the kind that feeds cows for meat and milk) knowledge is being lost and replaced superficiality and ignorance.

Our personal experience, so far, is driving a horse and carriage, loading it up in the field and unloading into a somewhat messy haystack.

I don’t know if our hay-skills will improve much as we hope to decrease our need for harvested hay, reduce the amount of land where it grows and probably hire machinery to cut it down and bale it for us in the interim.

Numbers in the Village

We went out to make a few arrangement in the village today.

300

We stopped in the village office building to pay our yearly taxes. There was an elderly man at the payment window. He was holding a thick pile of money all 1 lei bills. I am pretty sure he worked hard for everyone of those bills. His taxes came to just less then 300 lei. He was holding 3 packs of 100 1 lei bills. He handed them over to the lady behind the window and she began to count.

When the money was counted she handed him back his change. He was polite and humurous and said he had just enough left for a drink. She didn’t laugh.

We then paid our taxes and as she returned our change she said that there wasn’t enough for us to get a drink.

We then stopped at one of the bars to pick up a pack of cigarettes for our neigbor – and indeed the old man was there holding a drink.

We then went into a shop to get bread of our neighbor … and we decided to splurge and buy a (soft) drink too 🙂

6

Our yearly taxes came to a total of 1260 lei (it was actually a bit more because we got a few discounts for paying early in the year) which included:

  • Car: 936 lei
  • House: 6 lei
  • Yard: 71 lei (this supposedly includes some terrain around the house + the others structures on it).
  • Terrain: 301 lei (this includes the rest of the almost 9 hectares of land we own).
  • Fire Department: 12 lei (we’ve seen what looks like an old firetruck drive through the village center once or twice).

I am tempted to draw a few conclusions from this, but I am not interested enough to actually think them through and put them in writing. I leave you to it.

2

We then went to pick up 4 liters of milk – 2 for us and 2 for our neighbors (not the cigarette neighbor – different ones). The going village price of a liter of fresh milk (milked from the cow the same day) is 2 lei.

6000

We stopped at our neighbors to deliver their milk and chatted for a while. We are exploring with them a possibility to market their produce directly to customers instead of selling at the city markets (as they currently do). We learned that they pay over 6000 lei a year for renting a space in two of the city markets for 2 or 3 days a week. That probably accounts for at least 70-80 percent of their profits.

It wasn’t always like this. The markets used to be open-spaces where farmers paid a symbolic fee for selling their produce. Then the city decided to create better markets. It took away the open spaces, put them in the hands of private business-people who built closed spaces and now charge farmers a tremendous fee that eats most of their income.

You do the math. I started to, but I am to angered by it to actually sort it out and put it in writing. I leave you to it.

I can tell you this … if city people were to depend on me for growing food for them in this economic configuration, they would be going hungry.

Building an Earthship in a Cold Climate? STOP

… and read the book Passive Annual Heat Storage – Improving the Design of Earth Shelters by John Hait.

  • Should Earthships be insulated? Yes (but not in the obvious way it’s being done today).
  • Should Earthship floors be insulated? No.
  • Can an Earthship provide a comfortable (21c) climate using passive means during the winter season in a cold climate? Yes.
  • Can heat be collected and stored during the summer for a winter with very little (mostly cloudy) passive solar gain? Yes.
  • Can an Earthship be properly ventilated without having to sacrifice precious heat? Yes.
  • Are skylights a must? No.
  • Is the corridor wall (introduced systemically in Global Model) Earthships required in cold climate? Not necessarily.
  • Can an Earthsip be built in clay-rich expansive soil? Yes, if the soil kept dry.

When it comes to cold (moist and frozen) climates like ours here in Romania, there are quite a few things that felt, to me, incomplete, missing or even wrong in Earthship design (including the latest and greatest Global Model). To me what was missing most is the lack of explanations of how things work and why they are designed the way they are. I could not find satisfying answers in any of Michael Reynolds’ Earthship books (Earthships have evolved way beyond their description in the original Earthship books) nor online in many of the documented builds and open discussions about Earthships.

Then a few days ago I published this post about ventilation problems in an Earthship and began to compose my thoughts for a follow-up post. The solution seemed to come in the form of earth-tubes. The first resources I came across (pretty much as they were presented in the search results) were:

  •  Wikipedia – which provided basic technical information.
  • The Natural Home – which provided a convincing argument for earth tubes.
  • BuildItSolar – which raised some questions and left me with some doubts.

Luckily I stubbornly pressed through a few more pages of superficial search results and on the 3rd or 4th page found an article by John Hait inaptly titled Umbrella Home. The article blew me away. I ordered the book and couldn’t put it down – I read it word for word in just over a day and will be re-reading many parts of it again.

The book truly lives up to its subtitle “improving the design of earth shelters”. Not only does it open a door to a much deeper understanding of earth-tubes but to do so it introduces a fantastic concept of a large insulating/blanket which surrounds an earth-sheltered house in which earth-tubes can really come to life.

The core idea (backed up by accessible explanations and practical research) is to create an insulated and water-proof blanket that encompasses the house and a large area (~6 meters) around it (which can be achieved with more or less the same amount of insulation materials used for standard wall insulation).

This insulated umbrella creates a large body of earth which is dry and functions as a huge thermal battery attached to the house. The house itself acts as a solar collector to slowly charge the immense thermal battery during summer. Then, during winter that battery slowly discharges heat back into the house.

Earth tubes are used with this umbrella (in a way that could not achieved without the umbrella) to passively generate both ventilation and temperature regulation (cooling & warming) of the house. Because the earth-tubes run through the thermal battery surrounding the house they work as a super-efficient heat exchange system. A passive air-conditioning AND heat-exchange system that is simple and affordable.

 

As a cherry on top  – imagine running an uninsulated water supply pipe under the umbrella and having water preheated to 21 degress (celsius) during winter  (cold water supply has to be insulated under the umbrella). As someone who washes dishes with freezing-cold water (unless I fire up the wood boiler) I am watering at the mouth at the thought of washing dishes with passively heated (no additional energy expense or effort) warm water. Not to mention energy savings in heating bathing water.

This may cause a problem with Earthships that include rain-water harvesting stored in buried cisterns. The cisterns, if buried close to the house, under the umbrella will become a source of warm water. Cold water would have to be cooled somehow and I don’t know what effects this may have on the stored water. Since we’ve decided to forgo rainwater harvesting and put in a green-roof this is not a problem for us.

If you’ve already built an Earthship in a cold climate and it isn’t functioning as well as you thought it would I believe that at least some of the measures described in the book can be added to your Earthship to make it a much better home.

I don’t recommend trying to implement this from the basic information in the article. I STRONGLY recommend reading the book word for word. It is educating and empowering and fun to read.

I am now (again) heading back to the drawing board to revisit and rethink our house design. I feel I know better now and I am grateful to John Hait for his work and for making it available to others.

Earthships and Ventilation in Cold Climates – Problem?

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.

Saturday - January 14, 2012

Strange and powerful day today … started out beautiful snow white and sunshine.

I brought in the chainsaw, sharpened it and went to work. Finished a tank of gas and went to reload it. Couldn’t get it going again … it started but shut down numerous times … then wouldn’t start. Not good! Read the manual, searched online … couldn’t get it fixed.

I spent some really pleasant time in the workshop. Months ago I found a couple of old hardwood boards in the barn attic and I carried one of them down. Today I simply spent some time with it … no agenda, no rush … just planing and sanding a beautiful peace of wood … revealing and discovering it. It was a first-of-a-kind experience in the workshop … and I look forward to many more like it … hopefully … a whole lifetime 🙂

I tried the chainsaw again … still no good.

Then at the end of the day I went to the summer kitchen to bring in some tea … and I found the large shelves filled with all of our winter preserves half collapsed. One side seemed to pull down on the whole thing … fortunately it was stopped by the large barrel of pickled cabbages. The shelves were loaded with ~150 jars of food.  Three bottles of tomato sauce is all we lost. It was divine intervention … we should have lost almost all of our winter preserves … and yet only 3 bottles broke. Amazing. We took down many of the jars … to the point we could get it pushed back into place. Learned a woodworking lesson (more on that in a future post) and gifted with another generous share of gratefulness.

Snowstorm 1

I’ve been home alone for the past two days and so I am also alone in my first snow storm. This morning started out wet – it was slushy – a mixture between snow and rain … and muddy. The prevailing outside color was brown (the previous snow had already melted). Then the slush became just rain … muddier. Then … the sun came out for a short peek … then it went back into hiding. Then, all of a sudden, a snow storm set. Within an hour everything outside was white again.

It settled and this is what it looked like a few minutes ago – mind you these images were taken in color and are displayed as is – this is the fantastic palette outside now 🙂

… and the flock 🙂

It’s now snowing heavily again and I need to go out and collect Andreea from the village center – it’s snowing again so – my first drive in a snow storm 🙂

Water – Digging

There was quite a bit of digging (manual and machine) involved in our water infrastructures. I can point out for distinct efforts: (1) a cement box for the pump; (2) a cement box for main supply valves; (3) a long trench for a water pipe and electricity; (4) getting water in and out of the house.

Pump Box

Having decided to go with a surface pump we needed to create a freeze-proof space next to the well to install the pump. I suppose it’s possible to build some insulated box above surface but the recommended solution is an underground cement box. I started digging this hole by hand before we moved out and it was loads of difficult physical work.

In this image, taken while the well was being prepared for cleaning, you can see the hole in progress.

When this dig was completed there was a hole over 1 meter deep and 1 meter square in the ground. It needs to be large enough to accommodate the pump itself, some plumbing and a person who can move around inside for installation and maintenance work. In the image you can see the hole into the well and the beginning of an exit trench towards which the main water supply pipe will be installed.

A few small tips and things I would have done differently:

  • Make the hole into well in line with where the pump will be installed so that the pipe from the well does need to bend (beyond coming out of the well).
  • Do not begin the ditch for the pipe before completing the cement box. The earth walls form the outer form for the cement box. By starting the ditch I complicated the form work since a part of the earth was missing.

The inner forms for the cement box were built outside

… and then lowered into the hole in the ground followed by rebar to give the cement walls structural integrity.

Here you can see the layers of the inner form-work, the concrete rebar, and the outer earth.

The cement was poured in (mixed in an electric mixer and carried over in a  wheelbarrow) and when the forms came off we had a nice box.

Complete with holes fitted with 10cm PVC pipe into which smaller feed pipes will be fitted later.

And then immediately work began on the box cover. A wooden frame was created at the top of the box.

On  that frame they laid down a wooden “floor” (if I remember correctly they also put in some posts inside the box to further support the “floor” form). Then added some more rebar. On top of the rebar they added a manhole cover (which is supported on another partial wooden frame and ultimately set in the concrete) and an outside form to contain the poured cement.

Our concrete mix was a bit thin because we did not have gravel on-site and there wasn’t enough justification to bring in a truck load (even a small one). We did however have a large pile of sand with very small rocks in it leftover from the concrete floor that was placed inside the house. This meant that we needed more cement in the mix (gravel provides much of the volume in typical cement mixes).

The whole thing is supposed to be setup with a slight slope to the side and back (away from the well itself) to drain water away … I am not convinced that they put in enough slope.

And this what the result at the end of the concrete work.

A few days later (during which we watered the concrete numerous times) they came and hacked through the manhole opening with a chainsaw and pulled out the remaining forms.

The floor of the box remained pack-dirt so that excess moisture could soak away. Inside the floor they dug a hole 30cm deep which served as a foundation for a small concrete platform (~15 cm high above ground) upon which the pump itself would be installed.

Then came another precious lesson about working with professional, especially Romanian professionals. The pump is anchored with anchor bolts (bolts that are set in the concrete). I had already given some thought about how to place those bolts precisely enough for the pump base (which has very little tolerance). The solution I came up with was to comfortably (outside the cramped space of the concrete box) create a simple wooden template which would mark correct placement of the screws. Then the screws would be attached to the template, leaving as much as needed sticking out and the template would be placed in the concrete.

Still sounds like a good plan to me but they didn’t think so and I (through Andreea’s translation) was not demanding enough. So they did it “professional Romanian” style. They carried the pump out to the well and measured the distance between the screw holes and “copied” those measurements to the fresh concrete.

It was particularly disconcerting when, after rough measurement they placed the anchor bolts in place and jiggled them around a bit to get them to set well in the concrete.

When I came to install the pump I could just barely get two of the screw-holes onto the anchored screws. Of course it didn’t fit – why should it? Luck? By then the professionasl were already paid and too busy to come back and fix their work (hold on to your money in Romania until work is completed to your satisfaction) so I finally had to purchase a disc cutter (which has been an extremely useful tool, much more then I expected it to be) and cut the existing bolts, purchased bolts that could be drilled in (rather then set in the fresh concrete), drill holes for new ones and cut the new ones to size

Note: if you want to be able to get a nut onto the bolt you better cut it straight and level … not a trivial thing to do crouched in a confined space in the ground. I definitely paid for their stupidity – but as always I got a precious lesson in return.

Trenches

We hired a local excavator to dig an ~80 meter long and 110 cm deep (well below the freeze-depth of about 80 cm) trench then went from the pump-box to the back of the house where eventually a pipe entered the house. The dig started from behind the house.

Down towards the road

… and then across it

and across to the well-box

Not long after that a 32mm HDPE pipe and a protected electric cable were laid in the ditch which, for the most part, was quickly backfilled.

A protection measure can be taken for the pipe and cable  – and that is to place them over and cover them with a layer of builders sand which is better draining and also acts as a cushion against the heavy and expansive clay soil. We didn’t do this mostly due to costs – we would have needed another truck load of sand and would have to pay for more excavation time (for lining the trench with sand before laying the cable and pipe and then covering them with another layer before backfilling the trench).

 Junction Box

A second concrete box was excavated and built to house both a main filter and a junction point from which the water supply could be split to numerous destinations (including the house, a future connection to the summer kitchen, a future new house and an outside water supply in the area surrounding the house). This time, and in a matter of minutes, the tractor completed the excavation and the concrete construction process was repeated a second time.

Stay tuned for a closer look at the actual pump installation, plumbing and electricity.

 

 

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.