Let us suppose that the cost to build a conventional home is $100,000. To build the same home, but as a straw bale home, it would cost about $130,000. For cob, provided that you paid for the labor (as you did with the conventional home) about $170,000. And an earthship would ring in at about $180,000.
This always struck me as a bit frustrating. I wish there was a way to build a natural home that would cost less than building a conventional home. It seems that if you use materials from the land where the home is being built, you should be able to dramatically cut building costs.
I was exploring an opportunity near Kalispell many years ago and would need to build something cheap and quick. I started merging a lot of ideas together and came up with something I later called “wofati.”
Imagine living in something that looks like a log cabin from the inside, but with more light. It doesn’t need heat in the winter or A/C in the summer. And the cost, including labor, works out to about half.
This is mostly a combination of the designs of Mike Oehler and John Hait. Mike lives in Bonners Ferry and he has a home he built for $50 that is still standing strong 40 years later. John’s designs were invented in Missoula. So, this is a local product!
Here is a picture of our finished wofati 0.7 at Wheaton Laboratories:
The Wofati structure is the ultimate “eco” building, with up to 90% of materials coming from one’s own woodland property by using what can be cut when doing sustainable forestry thinning. No importing straw bales or dump truck loads of sand. In fact, most everything imported could fit into one pickup load: some doors, some glass, and some plumbing and electrical stuff – all of which you would bring in for any type of house.
In a nutshell, Mike’s design is a pole structure with a green roof. A green roof is usually 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: every drop of rain must always have a complete downhill soil path. Encountering the edge of the roof is not okay. And John basically extends Mike’s ideas to include a cheap means to eliminate the need to heat. Essentially by surrounding the structure with 20 feet of dry dirt to produce an enormous thermal mass. It’s mostly laying down some extra plastic sheeting during construction.
The basic wofati design principles are:
- Every drop of rain must always have a complete downhill soil path. Encountering the edge of the roof is not okay.
- There are two layers of polyethylene. The lower layer, which hugs the structure, and the upper layer, which defines the thermal mass that surrounds the structure. The upper layer must cover at least twice as much square feet as the available square feet in the structure.
- The uphill side has at least three open trenches to move water around the structure.
- The uphill side has a roof that extends at least three feet beyond the exterior wall.
- There is at least four inches of dirt between the two layers of polyethylene. There is at least sixteen inches of dirt on the top layer of polyethylene.
- The inner pole structure is made of logs.
- No treated wood is used in any of the structure.
- All polyethylene is surrounded on both sides by at least 10 sheets of newspaper. If the wood shell is unmilled logs or poles, much more newspaper must be used.
This is what the term “Wofati” means to me:
Woodland. The word “forest” suggests “forestry” which embraces a lot of things I don’t care for. A forest is …. used. A woodland is …. something that you are part of. Well, the key to making this word the highest priority is that this whole design would be silly if not built on, or very near, a woodland.
Mike Oehler. 80% of my design is standing on the rather brilliant shoulders of Mike Oehler.
Freaky-cheap. There are lots of easy ways to design a house that is even more costly than Oehler’s original design. In fact, Oehler is moving in that direction. He has been called on to design several houses and his designs have evolved into replacing some polyethylene with the more expensive EPDM (pond liner). He has also introduced the use of some commercial insulation. I, on the other hand, have come up with things that meet the same concerns that end up costing even less. I’ve run these ideas by Mike and he agrees that they are sound! (Yeah baby!)
Inertia. John Hait’s book is called “Passive Annual Heat Storage” – but what the title leaves out is that this design also brings a great deal of cooling in the summer. I think the phrase “Annualized Thermal Inertia” is more accurate.
Basically, if you live in a woodland, I cannot imagine any building technique that would be more eco than a wofati. This has more than 90% of the building materials coming right off the land it is built on. A tipi made of skins could be more eco I suppose. A log cabin could be almost as eco – if you build it Proenneke style. But not only is a wofati the ultimate eco building, it is a powerful way to truly connect to your land.
Here is the link to the original article I wrote 6 years ago:Wofati Eco Building