comparing wofati to earthship

Hey everyone,

I recently got Paul's e-mail about his wofati presentation. You can see a visualization and lots of info on that concept here:

http://www.richsoil.com/wofati.jsp

It's definitely an interesting concept, especially for how cheap you can build one. Seeing the utilization of the thermal consistency of the earth to cool a building is exciting, as it's an idea that I feel has been overlooked/underutilized in the construction of ecological housing.

However, I'm curious if anyone is familiar with the Earthship concept, and if so, if we could possibly discuss the pros/cons of these two, and in the end, which is a more ecologically sustainable method of building. If you're unfamiliar, you can get pretty much all you need to know at:

http://www.earthship.com

Just from my superficial impression of the wofati, I would tend to think the earthship concept to be a much more permaculture guided house, simply because of how many different functions the earthship provides. Let's break it down. With the wofati, you get:

1.) The use of locally abundant materials.
2.) Passive cooling.
3.) Minimal ecological displacement, since the roof is green.

With the earthship, you get:

1.) The use of locally abundant AND recycled/otherwise waste materials.
2.) Passive cooling AND heating.
3.) Minimal ecological displacement, since the thermal swale can be planted.
4.) Electricity production.
5.) Water harvesting.
6.) Waste water treatment and reuse with the added benefit of...
7.) Indoor year round food production.

So just based on that basic analysis of functions, it seems to me that the earthship is a much more integrated and holistic system. Of course, you could integrate all of those things into a wofati, but they are not necessarily intrinsic in their design, as is the case with an earthship.

Anyone have any thoughts on this?

Hum... the first thought is that although interesting, comparing the two is like comparing apples to oranges. They really are two different ducks.

Have you seen the price difference between the two? This explains much of the difference in the features list.

And I believe you'll find that when you try to do a serious comparison (of almost anything) logic and science take second place
to what people like, what moves them and inspires them. People then find facts to support where their heart is leading them, and
who can blame them life is to short.

Both styles have their advantages and disadvantages, both are alternative, use available materials and resources, but I wouldn't
build either. Unless I really needed to hide, and then it would be the wofati as it's more hidden. However, I have all the Earthship
books I II & III, and plan on incorporating much of the science into a cob cottage (yes, I vote for the one you didn't mention )

Sorry I can't be more analytical, to me it's all relative.

Maybe someone else will have some another perspective on the two.

The Wofati style is an interesting concept. I like Paul's ideas, but I'm not aware if one has actually been built yet. It would be great to visit one and stay in it for a few days to see how it feels and functions.

Earthships are very nice, I've been in a number of them in New Mexico and Colorado. I even planned to build one in Colorado when we were living there, but ended up having to move.

They are a lot of work, but you get a lot of return for your investment. I agree with Jami in that any kind of house construction has to be based on individual choice. It is all about what you need and what you would like, vs what you can afford and are willing to do.

In my opinion, the earthship basic concept is simply a high mass passive solar construction technique. All the other bells and whistles are not required and have pretty much evolved as time has passed. I like the other elements of the infrastructure as it stands today (water catchment, treatment, power generation, etc...), but they can be designed in any house construction model, for the most part.

One aspect that I'm surprised at with the Earthship concept is the food-raising approach. There are a lot of mentions of raising food in the home along the greenhouse area by the windows, but very little has been published or studied in any kind of rigorous manner. how much of your food CAN you raise in an earthship? It is very cool to walk in to an earthship and see a papaya with ripe fruit, but it comes off as a novelty in the books to me. I'd like to see an experienced permaculturist take on the challenge of seeing (and recording) how much food can be grown in and AROUND an earthship over the course of a year. Taking full advantage of the captured water, gray water and water redirection off the back and sides of the buidling, I'm betting it would be quite effective even in a relatively dry climate.

One other aspect that I've learned, having dabbled with the earthship building method (rammed earth inside tires) is that packing the tires with both sidewalls intact is the most laborious part of the process. I've seen info stating that if one of the sidewalls is cut off (jigsaw?), the method works just as well and goes MUCH faster. I have yet to see any info from the general earthship community on this method, though.

Thanks for your responses.

So I guess the part I missed that is extremely different from the earthship is price, with the wofati coming in at $500 if you want to get fancy. That's definitely an important factor.

K.B., I also noticed that the food production was a sort of secondary aspect of the earthships that I've seen, and I agree that I would like to see that possibility taken to it's fullest realization. This, to me, is what really sets the earthship apart from the wofati, is that you can produce food indoors year around, and I think that if this aspect of the earthship is further explored, to the extent that you could grow all of the food you need to survive, that's what would make the earthship a better overall option in terms of self-sufficiency, which is (from my understanding of it) what permaculture is largely about.

More input is definitely welcome, so others please chime in!

Rob Meyer wrote:

With the wofati, you get:

1.) The use of locally abundant materials.
2.) Passive cooling.
3.) Minimal ecological displacement, since the roof is green.

With the earthship, you get:

1.) The use of locally abundant AND recycled/otherwise waste materials.
2.) Passive cooling AND heating.
3.) Minimal ecological displacement, since the thermal swale can be planted.
4.) Electricity production.
5.) Water harvesting.
6.) Waste water treatment and reuse with the added benefit of...
7.) Indoor year round food production.

Anyone have any thoughts on this?

One could incorporate all of the features listed in the Earthship into a wofati design.

1.) The use of locally abundant AND recycled/otherwise waste materials.

This can easily be applied to both.

2.) Passive cooling AND heating.

Proper orientation of the glazed surface should cover your heating needs. In very cold regions or areas without much sunlight a double green house could be used. Basically a greenhouse over the southern exposed glazed windows. This acts essentially like double paned glass, there was an Earthship built in Scotland using this technique.

3.) Minimal ecological displacement, since the thermal swale can be planted.

The roof and thermal wrap of the Wofati can also be planted, probably a similar % of surface area of the building.

4.) Electricity production.

Earthships don't produce electricity, PV panels produce electricity. Place a PV panel on a Wofati and now your Wofati produces electricity, well the PV still produces it but you get what I'm saying...

5.) Water harvesting.

Can be applied to both, slope leading to a buried cistern. Could even be the basement of the Wofati...

6.) Waste water treatment and reuse with the added benefit of...

Again can be applied to both by integrating the Earhship mechanical systems into a Wofati.

7.) Indoor year round food production.

Should be possible with either design with an attached green house. The only Earthship I have seen with a large enough green house to produce a substantial amount of food is the Phoenix model. Though at a 1.5M price tag one begs to ask the question how is 1.5M for a "sustainable" house sustainable?

I really like everything about Earthships, except for their cost and the amount of labor require to build them. In Michael Reynolds movie, "Garbage Warrior" he mentions that his new path is one for trying to make them cheaper to build perhaps a type of hybrid Wofati Ship is on the way, if not from him, from us.

Hey Brad,

Thanks for the reply, good points all around.

Something just came to mind that may be a detriment to the Eartship model. It uses recycled materials, i.e. bottles, cans, and mainly tires. By doing so, it removes these products from potential landfill, but it also removes them from recycling, which means more fresh materials will be required to continue to make those materials. On the other hand, if those materials were recycled into new tired, bottles, or cans, the mining of new minerals/extraction of new rubber could be avoided all together, so long as there is enough recycle-able material to provide these products.

So in the end, is it the earthship model that is less sustainable than the wofati? You're quite right that the earthship is a bit on the high side for eco houses (although compared to regular housing, it's a drop in the bucket), but perhaps a balance could be made between the totally renewable materials based wofati and the partially recycled material earthship, using only renewable materials found for free or cheap in the area, while still integrating these self-sufficient systems in the house's interior. The problem I guess is that the Earthship has been doing it for so long, and has the designs down to a science, so you may have to spend some money on at least their schematics to see what they've found to be the best way to approach things like energy and water treatment. On the other hand, I'm sure that if one looked, you could find a lot of that info out there for free or cheap.

So, if anyone has any resources on these systems, as well as resources on earthen building/solar passive heating and cooling, I'd like to try to develop a sort of evolved form of the wofati that integrates the systems of the earthship into the mix, giving an extremely cheap yet self-sufficient model of housing that can be build very easily. Anyone wanna help?

Good discussion and agree with most comments. On costs, if an earthship was kept to scale with Paul's wofati pics then I imagine the costs could be very similar. Likewise if the Wofati was done on a bigger scale closer to some of the Earthships then its price would dramatically increase. Not sure what kind of life time is expected out of the Wofatis but to me, buried softwood (of un-rot resistive species) protected by a thin and fragile layer of polyethelyne would have a very short life span on the east coast. Overall its a very permie approach but dirtwork is very invasive and with such a short lifespan...

As for significant food production inside living space, forget it. There is simply not enough room or space. I must be missing something on rainwater capturing off of living roofs because from what I understand, metal is the best material for this. Dirt and plants soak up too much water to go through trouble and expense of capturing whats left over.

For those interested in cost effective passive solar design, check out my new article on GreenBuildingAdvisor: http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/cost-effective-passive-solar-design

Great point S.H., I hadn't thought of that.

So to sum it up, if you want a small one or two person temporary shelter that will keep you pretty warm and dry for a few years, and eventually decompose back to the forest, the wofati is your design. If you want a long lasting inherently self-sufficient permanent dwelling, the earthship is where to look. Thus why I would still say that the earthship is the best PERMAculture designed house, since it's so permanent and holistic by nature.

I'm still a bit hazy on the cans/bottles/tires issue. I mean, they're not inherent in the design, and I would imagine you could make one with as much thermal mass using earthbags, cob, or strawbales instead of rammed earth tires. Or, perhaps you could use the brick maker from the global village construction set that was designed by open source ecology, and use those as your wall material. In any case, I am still curious if removing those materials from the (re)cycle would indeed have the negative effect I mentioned. Should we be advocating for recycling over reuse? Is there a certain point of reuse that is actually detrimental to the environment? I guess perhaps this is a topic to ask in a new thread...

Learn from both designs and create your own hybrid using your imagination.

Rob Meyer wrote: It uses recycled materials, i.e. bottles, cans, and mainly tires. By doing so, it removes these products from potential landfill, but it also removes them from recycling, which means more fresh materials will be required to continue to make those materials. On the other hand, if those materials were recycled into new tired, bottles, or cans, the mining of new minerals/extraction of new rubber could be avoided all together, so long as there is enough recycle-able material to provide these products.

I didn't know much about the process of tire recycling, so I did a little research - this site says

Annually, more than 250 million scrap tires are discarded in the United States.

and the wikipedia entry on tire recycling says

A report from 2003, cited by the EPA, says that markets ("both recycling and beneficial use") existed for 80.4% of scrap tires, about 233 million tires per year.

so that's >17 million tires per year that don't have a market. Unsure whether that's because not enough recycling facilities exist, or because the tires are in some way not worth recycling.

a post from "Matt Lew" in the comments of this ecogeek article on earthships says:

I have read that the average earthship takes about 2000 tires

assuming those numbers are correct, that would mean that there would be sufficient unrecycleable tires to make 8500 earthships per year.

Even if only half of the unrecycleable tires are still useable as bricks, that's still 4250 potential earthships.

Now, obviously that doesn't take into consideration the location of the tires, or whether it'd be easy to transport them to the building site. The point I was trying to make is that there's a lot of material out there.

Wow dave, great info! Good to know.

Not to rain on anyone's parade or anything..... but as I read this two things pop to mind.

(1) There is starting to be debate over the health of those living in houses made with tires - you can do a search here at permies, it's all been covered here before.
I only read about it, but apparently the tires do off-gas even when covered with soil. You can also google it.

(2) And it is not possible to raise even half your food in a 'house's greenhouse. Some of the points are covered in Paul's article on greenhouse suck factor. The biggest problem is the amount of constant carbon dioxide (fresh air for plants). A large volume of plants means air, moisture and light management - the more you grow the more you have to manage. People have asked 'how green is this' when one is spending lots of time and resources to grow plants in an artificial environment. Basically it boils down to, you can only realistically grow a small percent of your total food needs in a greenhouse attached to your house. And after saying all this I still plan on having a greenhouse on my house for passive solar gain but growing plants will be the least of what it will do for me.

I'm not saying Earthships are bad, or that people shouldn't consider them as a choice, just that a deeper look may be warranted.

There has been a lot of speculation regarding tire off-gassing when embedded in earth, but not much science/study that I have seen. Most of what I have read has been based on a general "icky" feeling that some folks have with the idea. Everyone has different comfort zones, as with all things.

I encourage folks to visit a functioning earthship. the feeling indoors is very comfortable and alive. well worth experiencing.

Regarding how much food production can occur in a greenhouse portion of a house, I'm not sure of the answer. I think it could potentially be quite a lot of volume, but maybe not so many calories. However, until someone trys it and documents it, I will remain curious. Root crops could be planted intensively with quick succession cycles and the several hundred square feet may be able to produce more than some think. perennials would me more my choice, but that's just my preferences.

When the grow beds are along the windows of a passive solar house, the volume of air inside the home would be quite large in comparison to the smaller growing space. I don't think the limitation of only so much carbon dioxide would hold true in these conditions. Ventilation is straightforward using vents under the windows and skylights to allow for air flow.

The other factor that some newer earthship designs take advantage of, that could be incorporated in to any high mass solar design, is additional greenhouse and/or raised bed space on the south side of the house to utilize the extra gray water from domestic use. these spaces are outside the envelope of the main house but sheltered and can be connected via windows or doors.

Jami McBride wrote:
I only read about it, but apparently the tires do off-gas even when covered with soil. You can also google it.

I was trying to find information about this - either saying "yes they do" or "no they don't". The Earthship website mentions a report - "Use of Scrap Tires in Civil and Environmental Construction" May 10, 1995. Environmental Geo-technics Report No. 95-2. Geo-technical Engineering Program Department of Civil & Environmental Engineering." but I've been unable to find the full text of the report online. Earthship Biotecture do have an excerpt posted to their site.

Additionally, they quote an email from Chris Kaiser, who is identified as an engineer in Colorado, and who says he's not affiliated with Earthship Biotecture:

to assess the risks to human health and environment posed by the use of recycled tires in Earthships, one must look at the pathways of exposure, and the state in which this potential contaminant exists. The letter states that, "A tire under proper conditions will break down into the above products." "The proper conditions" for rubber to degrade would be: high temperature, exposure to light, or the presence of strong oxidizing chemicals. None of these conditions exist when a tire is entombed in an Earthship wall surrounded by packed earth, vapor barrier, stucco, and paint. The argument has been made that tires must off-gas because "old tires smell." The reason "old tires smell" is due to the photo degradation of rubber. Essentially what happens is that photons from light bombard the rubber and knock atoms from the long rubber polymer molecules. This causes the rubber to degrade, and smaller molecules to vaporize. In the absence of light, this does not happen.

Tires are not exposed to light when used in an Earthship. In order for the tires to affect the indoor air quality of an Earthship, the tires must off-gas vapors which must travel from the tires, through the walls, into the living space of the Earthship. The production of such vapors will be proportional to the vapor pressure of the compounds producing the vapors. The NIOSH pocket guide lists the vapor pressure of carbon black as "0 mm (approx.)." This is an extremely low vapor pressure. In other words, this chemical produces almost no vapor. What this means is that the potential for tires to affect indoor air quality will be severely limited by the extremely low vapor pressure of the source chemical.

The letter also states, "We do not need these products leaching into our water systems." In order for a tire to affect water quality, it must come into contact with water, and release chemicals into the water. In a properly designed and constructed Earthship, there will be no flux of water through the wall. Therefore, no water will contact the tire. In the unlikely event that water should contact the tire, the water will not become contaminated because carbon black is insoluble in water (NIOSH Pocket Guide).

Just some things to think about. The "contact with water" bit made me think, well, maybe Earthships are a great design for the climate of NM, and perhaps other designs could be developed for other areas, where dampness is a much bigger concern, or for people who would feel better about no tire proximity.

Jami McBride wrote:(2) And it is not possible to raise even half your food in a 'house's greenhouse. Some of the points are covered in Paul's article on greenhouse suck factor. The biggest problem is the amount of constant carbon dioxide (fresh air for plants). A large volume of plants means air, moisture and light management - the more you grow the more you have to manage. People have asked 'how green is this' when one is spending lots of time and resources to grow plants in an artificial environment. Basically it boils down to, you can only realistically grow a small percent of your total food needs in a greenhouse attached to your house. And after saying all this I still plan on having a greenhouse on my house for passive solar gain but growing plants will be the least of what it will do for me.

I'm not saying Earthships are bad, or that people shouldn't consider them as a choice, just that a deeper look may be warranted.

Agreed on the amount of space needed for growing large percentages of one's food. It just doesn't seem feasible to plan on an indoor-only setup. I see Earthship gardens as a convenient greenhouse, but like you said, part of stacking functions.

First thing, Earthships are copyrighted and you need to pay the Earthship people for a design. This costs a good chunk of money. It's not free.
Then if you use their systems, an average house runs in the 300,000++ range. Not a great deal in my opinion.

You can have all the features and benefits of an earthship without the extreme expense of an earthship by building a wofati or Oehler underground home. You can add solar, water collection, even grow a garden on your roof. Using Oehlers methods you can build an underground greenhouse for next to nothing too.
You can incorporate water catchment, greywater use, incorporate recycled materials, whatever eco-features you want.
You don't need an overpriced architect to design it either. With the money you save you can afford more eco-features.

And yes, very large lived-in Oehler designs exist, one example is built by Glenn Kangiser who is on this forum.
http://www.countryplans.com/underground.html

I visited the earthship folks and own the earthship books. I liked the homes, but not the pricing structure. They are also not necessarily appropriate for all regions.
The only advantage I see is you can build a permitted Earthship in New Mexico, but outside of New Mexico, good luck. You are not going to get a permitted wofati/oehler structure. If you have remote land (like me) or building in an area with no permits required, do what you want.

I found both concepts excelent, and each one is adopted to different investor's needs and resources. I'm designing my own house as I did not find any of existing fits my own needs, for example I don't like Earthship's huge glazed surface compared to relatively small house volume. This house must be extremly dependent on the sun. When there is plenty of it, house must be quite warm during winter. But during a couple of days of cloudy weather house looses all captured heat and gets quite cold if you don't start a fire. It does not fits my needs so I went in direction of creating a much smaller windows and 2 story underground house, which fits my needs and resources perfectly.

Also, in my area I can not get tires for free, I have to buy it but only after I explane why I need so many of it, get special licence to use it as building material (so far impossible) and so on.

It is only an example why would someone prefer one or another concept, or why would one use some parts of each but build something different.

why would anyone want to pound 2,000 tires? That's a lot of work, and thank goodness they aren't paying for labor...

We use a modification of Oehler's PSP method. Earthbags could work, too.

As far as growing your food inside, we have a small area on our south wall. It is about 18 feet by 1.5 feet. We have 3 LARGE cherry tomato plants there, and we never have to buy tomatoes. We also grow greens, mint, basil, etc. It is not all the food we eat, but we can make a meal per day from it (usually a mixed salad for lunch) for the family.

velacreations Hatfield wrote:why would anyone want to pound 2,000 tires? That's a lot of work, and thank goodness they aren't paying for labor...

We use a modification of Oehler's PSP method. Earthbags could work, too.

I just read the new Earthship Global Model Operation One: Tire Work book and they say the 2 bedroom model uses 750 tires. I think the old models where they used several interlinking horseshoe shapes used much more tires. I agree that an earthship could be made from earthbags however I cannot visualize how to attach the bond beam. I think the Earthship could be made nearly as cheap as a wofati but will require different skills ( I say different because a wofati looks fairly equipment, woodwoorking skill intensive).

Tires: Free or may even get paid to take them
Dirt: Free (thermal mass, walls, floors)
Roof: Maybe less expensive than wofati (doesnt need to support living roof) but does require a metal roofing system which is expensive.
Insulation/Waterproofing/Thermal Mass: Same as wofati
Windows: Same as wofati? Maybe more unless you do some creative sourcing.
Offgrid power: wofati requires a well pump and probably water softening which have large power requirements ( a well pump cant be DC due to the head needed on the pump) while Earthship systems have very low power requirements (they recommend a 2kw solar setup - about 8000$ if you do the install and before any rebates) and run completely DC- AC is only for convenience and the rooftop rainwater catch uses gravity instead of fighting it. Rainwater needs no softening.
Sewage: Water softeners make septic tanks not work well due to the high salt content not to mention engineered wetlands.
Labor: Earthship more but possibly made up for in longevity? Wood underground just seems problematic. A wofati seems to require more digging while an earthship is built on the surface and bermed.

I don't know why you suggest that an earthship would have a lower power requirement than a wofati or any other bermed or buried building. Water doesn't have to come from a well. You could catch water from the wofati, too (or a barn, shed, or other outbuilding). There is no reason you can't put a roof material on a wofati to catch rainwater. But catching rainwater doesn't get water to your shower heads. You will still require power to pressurize it.

I have a buried home (ferrocement, CEB, PSP) that we built ourselves. We have a 600 watt solar system. We have rain catchment (6500 gallon cistern). We have indoor greywater gardens and passive+active solar components. So far, we have about $8,000 into this home, including labor, windows, doors, floors, etc. It is currently 1300 square feet. This is the second off-grid home my wife and I have built in the last decade, and we rarely have more than $2,000 on hand.

When I looked into building an earthship, a great disadvantage became apparent - you have to haul all those tires to the home site. Tires are bulky and dirty. You add a significant cost and trouble by having to haul them. They are not as easy to get as some people have you think. I was going to have to pay $2 a piece to get 1,000 within a reasonable distance from the building site (100 miles). Instead, I bought a metal roof for $3,000 and made a pole barn. We then made an adobe home under the roof.

Earthships require stucco/plaster on the walls, adding significantly to the cost and to the labor. There is no comparison on labor, wofati wins hands down. PSP is even better. And my system of PSP is even better than Oehler's.

Bottom line is, I don't like pounding tires, and I would not do it 1,000 times or more. I would rather backfill a PSP wall or tamp an earthbag (significantly faster, cheaper, easy to haul, and doesn't offgas). Earthbags require a fraction of the soil required for a tire, and perform as well or better, if designed properly (passive solar, etc).

Earthship technology was a great start, but in my opinion, there is nothing you can do with tires that you can't do with better materials, like CEBs, earthbags, PSP, logs, or whatever.

Separate the building technology from the supporting technology. Dirt can be used in a lot of ways to make a house. Offgrid power can work with any system (my solar setup is considerably smaller than the Earthship recommended size). Rainwater catchment can be made done on a variety of roofing materials (I prefer long-lasting concrete). Greywater reuse is easy on just about any home.

Once you realize that these systems don't require an earthship to function properly, you can integrate them into a better building method.