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.


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 ย relative stabilityย  for the under-layers.


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.


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.

It’s been three long days since I’ve gotten around to writing a short update.

They have been dominated by long days of work that culminated in completion of the last official wood-working project in preparation for winter. Two (rather large) open shelves with counter-tops are now assembled in the living room. The first one was assembled yesterday when the oil was almost completely dried on all its parts. The second took a short cut – it was assembled only half finished (oiled) and the remaining pieces (those I finished working on today) were oiled after assembly (this way they are drying in place instead of occupying a large space in the middle of the room – it should be dry by tomorrow.

Meanwhile Andreea has been mostly inside the house cleaning and organizing our stuff – all our clothes are in the new closet and tomorrow all the books and other stuff will go into the new shelves. Andreea also struggled with the old wood-stove. We haven’t used it in a few weeks (we spend all out times indoors in the bedroom) – so today she wanted to fire it up again – to get the room warm (helps the finish dry) and remove some of the moisture building up in it (moisture is a problem all year long and can cause much damage – so stoves need to be lit). Anyways, she lit up and again it began to smoke like crazy – it really bummed her out. I suggested she try using some heat-resistant silicon … and she worked on it for quite ย a while and got it all sealed off … fired it up again and this time heat without smoke! A big relieft.

It’s really starting to come together and it looks like we’ll be able to bring our Christmas tree indoors into a pleasant and clean house.

I’ll be spending most of tomorrow replenishing our fire-wood supply and if there will be time for it I will try to finish a few finishing pieces I want to add to the living room shelves. There are still a few projects but they are on the nice to have list – this includes a low-table for the living room, dressers and a headboard for the bed, another small creative cabinet in the hall kitchen for shoes, garbage and coats ๐Ÿ™‚ and on and on and on ๐Ÿ™‚

In the background of these 3 days has been a violent disturbance from the life we left behind in Israel. It is being resolved and hopefully will soon fade away from our consciousness.


Woodworking all day today. It actually started last night as I drew the two living room units in my head and made a cut-list. It’s a fairly simple project though lots of wood-surface is involved. Today I managed to get all the wood out of storage and cut to size. More then half of the materials have been planed. Some of the larger pieces that were later cut into smaller pieces were also sanded (with a few hours of help from Andreea who took to with a rough and medium grit (it’s easier to get large surfaces sanded before they are cut into smaller parts). So all the parts have been cut. I will probably be spending a few hours with the planer tomorrow and then the next two days with the sander in hand ๐Ÿ™‚ But I expect that in two or three days one of the two units may already be constructed … then our books can come out of storage ๐Ÿ™‚ The place is really becoming comfortable and pleasant to the eye ๐Ÿ™‚

Started the day in the workshop – finished the pieces for the couch. Then went off on a series of things that needed doing (humanure hacienda, breaking into the garage attic and storing it in the cardboard boxes that have been tied to the roof of the car for days, closing more of the water-supply pipe ditch to protect against freezing, dishes ..) and finally went inside to assemble the couch … assembly went like a charm this time ย – I am developing a system of wood-working: all straight & non-visible screws woodworking or ASNVSWW for short ๐Ÿ™‚

Long woodworking day. I started with raw wood and finished with an 80x180cm seat for the couch complete with hinges. I went further then I ever have with this one. I took a bit more care yesterday when I planed the boards – so that they were a fairly consistent thickness. Today I routed the edges of the boards to get them to overlap each other and they came together pretty well. After assembling them using vertical connecting boards on the bottom side I continued to sand them from rough to fine until I got a fairly nice surface … not perfectly even but closer then even before (it’ll be covered by a mattress so it isn’t too critical). I routed sockets for the hinges (which I’ve done before) and attached hinges (which I haven’t done until today – need to practice some more at this … the hinges are protruding more then I wanted them to) … and I had just enough light left to carry it indoors (heavy!) and lay it on top of the mockup model … looking good.

Tomorrow I want to prepare the back and two more pieces that need to be installed to support the box floor (I’ll do the box floor at a later time) and two additional internal support frames for the weight-bearing seat. Hopefully tomorrow evening the couch will be assembled ๐Ÿ™‚

Today started off a gray rainy day. With a little discipline I pulled myself out to work and as if responding to me the day began to clear until even a warm sun came shining through. Later it became a mixed day of clouds, sun and wind. By evening a chill had set in … undecided all around. It wasn’t a sunny day, but it was definitely a un-cold day.

Spent most of the day woodworking with woohooo results. We now have a large cabinet, shelves and all … even a large coat hanging space. It is “door ready” but there are not doors yet. I finished the parts early in the day and later in the evening, when there was no more light out, I came inside and assembled the shelf-hangers and then the shelves. Andreea is filling it with our things as I write these words.

I then moved to the first couch. I completed assembly of the two side panels and mid-leg support. I then continued to sand the rear and face panels and to cut and plane the seat pieces. Lots of wood-working-satisfaction tonight as there is now a mockup of our couch standing in the living room – looks like its going to be a great size. Still much work to do … but I think in a few days we may actually have a couch (at least the wood-part) to sit on. The couch will also have a large storage box … so that should come in useful too ๐Ÿ™‚

Already we are making plans for a simple living room unit that will hold lots of other stuff including our LCD screen, sewing machine and hopefully all of our books. Its feels like a bit of a race … but we want a pleasant and organized house and living room by Christmas ๐Ÿ™‚ Its time to leave the camp site and move into a house ๐Ÿ™‚

Yesterday we got back from a nice two rest in Targu Mures. The restfulness was replaced by restlessness from a long drive back home with a few stops in Cluj. But we made it back, made some mamaliga and slipped under the covers early.

Today was another typical un-cold day so we used it for work. We got all the cabinet shelves sanded and two layers of finish applied to them (thanks to a bit of un-cold fresh air with occasional sunlight). The living/finishing room floor is practically covered with shelves and shelf hangers. Tomorrow they all to through a little light sanding and then some polishing and then we can bring all home … and finally have cabinets (that one day will have doors too) to put all our stuff in.