When it comes to eco building, there appears to be a lot of enthusiasm for straw bale homes and for cob homes. Let's just note that if you were to pay someone to have a conventional house built for you, it'd be around $100,000. Say you want an eco home built for you, straw bale would be $130,000 and cob would be $200,000. In either case, this is usually nothing more than replacing the exterior walls. Cob could also be used for interior walls, but for the moment, I would just like to examine the simpler case of replacing the exterior walls.

With straw bale, the cost of the materials for the exterior walls is higher than a conventional home. The cost of labor is significantly higher, although some of the work can often be replaced by workshop labor. Unless you live on land that produces straw and you have a baler, you will have to buy straw and have it moved to you. The beauty of straw bale is the insulation. Straw itself is not a particularly good insulator, but a really thick wall of it is. Of course, to stay warm on a really cold day, it helps if you're sealed up inside like being in a ziplock bag.

With cob, you will need a source for clay and good sand. Sometimes you are on land that has clay, so then you just need a few dumptruck loads of sand. And the amount of time to build a cob wall is far greater than conventional. The beauty of cob is that you can shape it to anything! And it is soooooo easy to do. If you can supply lots of time, you can build a fantasticly lovely home from cob.

In the fall of 1970, Mike Oehler (pronounced "Ay-ler") lived in a crappy shack and struggled to stay warm. He decided that the following spring he would build a better place to live. He spent the winter drawing all sorts of designs to calculate heat efficiency. He also wanted to keep his materials costs low. He came up with a design that was unlike anything he had ever seen anywhere else. The result is a home built in 1971 with a total cost of $50.

Later, Mike added on to that house and then wrote a book about it. His choice of title was so bad, that I avoided the book for more than a decade. Even the pictures on the cover bothered me. It was only after seeing so many other authors refer to the book that got me to look at a library copy.

Mike's design eliminates many of the complexities of conventional construction. Further, if you live on wooded land, most of the materials consist of what you cut from your land when doing sustainable forestry thinning. No importing straw bales or dump truck loads of sand. In fact, everything you import could fit into one pickup load: some doors, some glass, some plumbing and electrical stuff - all of which you would bring in for any type of house.

Mike then enhances his original designs to come up with a variety of ways to get sun into his structure from all directions, while keeping the costs low. After teaching dozens of workshops on his techniques, he puts the workshop on video. I have seen these videos. They are excellent.

In a nutshell, Mike's design is a pole structure with a green roof. A green roof is usally more expensive than a conventional roof, but, if you can follow one simple design principle, you can dramatically cut the costs of the whole structure!

The one simple design principle is this:



Every drop of rain has a complete downhill soil path and never encounters a roof edge.

I contact Mike and visit with him a bit. Now, his excellent design is easily confused with .... lessor designs. Designs which he thoroughly bashes in his book, but you will never find out about that if you cannot get past the title of the book (which is what happened to me). During our conversation, he told me that he wishes to now call his structures "Earth Integrated Structures". For the rest of this document, I am going to disrespect his wish and instead refer to these as "Oehler Structures".

Next, I found a copy of John Hait's book "Passive Annual Heat Storage". In that book, John appears to extend Mike's ideas to include a cheap means to eliminate the need to heat. Basically, surround the structure with 20 feet of dry dirt to produce an enormous thermal mass. It's mostly laying down some extra plastic sheeting and insulation during construction.