best doc i know on this topic, I would love to build and own one of these earthships, there is also a nice looking one in BC Canada and I would love to go see it in person.
http://www.youtube.com/watch?v=G7h1eRiJwow

I'll stay inside the box for some very basic reasons.

1 - Wood is the cheapest (*free for any landowner) building resource we have.
2 - Wood is the most abundant building resource we have.
3 - Unprocessed wood has the highest natural insulation value at the lowest carbon footprint
4 - Wood is the easiest building resource to shape, treat and strengthen
5 - Proper, climate-specific wood dwellings last longer than their steel and synthetic counterparts
6 - Wood dwellings fit & finish is superior to patchwork recycled-goods dwellings, providing better shelter and higher heating/cooling efficiency.

😀

Its all about $$$. If you have money, I'd steer right away from wood construction and go noncombustible. Block masonry, steel studs, etc. The cost is a lot more, but you negate a lot of fire concern, and your structure is more secure against inclement weather, crime and violence, etc.. Very secure. But again...a lot more expensive.

To build, you will need to get a professional designer to prepare the submissions to the building dept. and make sure your building meets all the codes. You can pick up kits already premade at most home depots or home hardwares, but if you want to do something custom and depending what jurisdiction your in, the size, etc. you'll need an Architect or designer (in ontario at least) with a BCIN certification.

We build with wood in Canada as its very cost economical. But I can't say its the safest material. Talk to a local builder to get an idea of price. They can give you a rough budget if you give them a rough idea of what you want (non combustible, square footage, etc.)

My personal choice:
I would build with poured concrete and insulated concrete molded walls, steel stud construction for any interior walls, and steel joists for a roof. No combustible material, and a building that could withstand a torando, a riot, or most any exterior element. Because of the cost of concrete, I would probably elect to go with Block masonry in lieu of concrete above grade...still expensive but at least a bit more realistic.

Of interest, back in the early 80's and late 70's concrete was a lot less expensive. There were some town houses, and homes built with Concrete walls and floors. Then to finish off the interior they simply laminated drywall to them to give it a home look. The exterior could be siding, brick, whatever. I have a friend who lives in one and he said the only down side is that to hang anything on the wall...you pretty much need a drill and a tap con. 🙂

The Olympic Village in Montreal is another example. Though they were "pods" and more condo style than a house or townhouse.

I installed windows in an all concrete/steel residence a few years ago. A very impressive structure for sure. Lots of positives, however one big negative is that it was essentially a sealed environment.

If it's HVAC system wasn't running at 85%+ efficiency, air quality dropped like a stone, the house couldn't "breathe" properly, mold growth exploded and if left long enough, the increased moisture would actually weaken the concrete in areas.

In a prolonged power outage, the place could become a death trap like any other, just not a flammable one.

We haven't learned to properly build concrete structures in humid climate environments yet. Contact with wet earth will bring the structure close enough to the dew point to cause lots of moisture trouble.
For the last year I've been working with an architect and engineer to develop plans that incorporate all my design requirements and still pass code. Unfortunately, code writers are stuck in the stick built world, mostly keeping inept builders from passing off shoddy structures as housing.
It's a long way off yet but I'll try to document the design and process.

I am heavily involved in commercial and institutional construction. Concrete and hardened structures are not common, but definitely doable. It's more of an economical issue than anything.

Have done significant work for correctional facilities, LE, and secured areas for institutional buildings.

Would be very interested in seeing your designs! I've been tinkering with my own, but maybe your design team is farther ahead. Can I ask who you are using?

My choice if I was able would be to convert one of those big old barns
I would use Geothermal heat and a combination of wind and solar power
Ideally would include some type of steel or cement shelter as well

I like that idea Muleskinner. I doubt realistically I would start completely from scratch myself but some attempt at partially double enveloping an existing structure with an earth bermed or somehow insulated concrete block or earthbag cold room on the north side of an existing structure and a greenhouse type extension on the south side would not be beyond my realistic capabilities . I already use a lot of repurposed free materials off craigslist , today I am using a heavy clear plexiglass mat that was manufactured for use under office chairs , will be repurposed as a safe barn window for a horse stall. Repurposing free resources of all types that put them to further use appeals to me .
Restructuring how we live too seems appropriate, for instance I have been noticing when not in use I have ceramic bowls, crocks, roasters, casserole dishes , jars, platters that do not require heated storage space and I am contemplating how to design outdoor storage space like an unheated butler pantry cupboard ? for them rather than build bigger houses or use pantry space for things that can be kept elsewhere and keep my kitchen and heated living space better insulated and smaller.
I am sure some clever thoughtful design and renovation could see climate appropriate housing that seems to be absolutely lost common sense to part of our society.

I've thought about building a cordword structure, but you need a long lead time to get all the logs cut and properly dried.

What is conventional depends where you live.

100 years ago the norm around here was timber frames with timber cladding, but now the norm is steel or treated pine frame with a brick veneer.
So I guess we have followed the norm from 100 years ago which is no longer conventional.

I saw Tiny Texas Houses online and loved them and even better we already owned the perfect building to demolish and re-build in that style.
We kept the inside conventional with gyprock and acoustic insulation for the sake of sound and speed. We built an all timber cabin previously on our old property and the acoustics were incredible which was not a good thing. Privacy and three musicians makes acoustic insulation in the walls and ceiling a must...single skin timber walls just don't cut it, you could hear a pin drop!
So on modern standards ours is not a conventional house...and I love it, even though we still need to do a lot of work to finish it off 😀

I know a very old school Greek immigrant lady whom literally glues styrofoam egg cartons to her walls and the science behind that unconventional sound proofing holds up, it might even be a better insulator ?

I'm intending to have a tiny house, as in tumbleweed type. It may be fairly soon, as an unfinished model has become available.
It's what i had been planning to build anyway, with different preferences/features.
It is certainly unconventional , as it is made of SIPS, with an R rating of around 30, all around, steel roof, and i may use exterior steel wall panels as it will be in the bush.
I'll have to finesse the convection currents/circulation with operable vents, incorporating a mini rocket stove/cooker.
Since it is on wheels, it is a mobile investment in the event that plans or circumstances change .
However the intent is to have a ready, 4-season structure/home-base which will sooner enable the building of other cabins and infrastructure.
Sure, i know its main feature is not a "natural" material, but as with many things in transition, i have no qualms about utilizing some of the "developed world technology" if it is a means to expedite a transition to greater natural relevance.

I still like an earthberm structure, with a geothermal mantle, auxillary passive solar collectors,.. and this will likely be my direction on-the-ground.
A colleague of mine makes adobe bricks and has also used them together with strawbale construction/double wall, increasing thermal sink mass greatly, and acoustic barrier excellence.

The issue with moisture connection to the ground , using cementitious products, is generally avoided by using vapour barrier and sufficient draining, aggregate base, or did i miss something about that? Was it more about lack of breathe-ability in the walls too?

I also love domes, having been involved in some of the first ones in can ada. The current refinements are impressive. especially for use as a growing house/aquaculture in any environment, but especially in hi-wind scene.

I know a very old school Greek immigrant lady whom literally glues styrofoam egg cartons to her walls and the science behind that unconventional sound proofing holds up, it might even be a better insulator ?

We thought about using styrofoam boxes but couldn't get enough of them in a short time and we could get the acoustic insulation at a wholesale price. Funny that almost all of the Tiny Texas Houses have an air conditioner installed, maybe they don't get a good breeze through them with the small windows?!?
Our internal space is 62m sq or 660 sq feet and has two adults and two adult size kids living in it, and we are still building the front porch which will add another 35m sq or 376 sq feet. I guess house sizes can also be non conventional, my good friend and neighbour pities me living in such a small house, they just extended theirs from 100m sq out to 200m sq internal space and then more for back patio and front porch...she just doesn't understand that this is what we are happy living in 😉
We have used as much recycled material or collected new material at wholesale prices and will pull the cost in at around $15k where as the neighbour spent over $150k just on the extension. I think this is a damn good reason to look at no conventional or small homes just for the cost savings alone.

The issue with moisture connection to the ground , using cementitious products, is generally avoided by using vapour barrier and sufficient draining, aggregate base, or did i miss something about that? Was it more about lack of breathe-ability in the walls too?

It isn't the moisture in the ground leaching through. Moist soil touching the thermally conductive walls transfers heat away and brings them down to the dewpoint, then condensation forms on the inside. You need a thermal (and moisture) break away from the foundation. The farther away, the more mass you have without packing tires or pouring concrete. Dry soil equals heat storage, moist soil is a heat sink, sucking it away and into the earth, gone forever.

In a dry climate this is not a problem. Earthships built in the desert don't have any issues - dry soil around the foundation. Move them to a humid climate and all the moisture/mold problems surface.