I recently got a query from one of the editors of Mother Earth News regarding a news story she had read in the New York Times. The writer, David Pogue, had been a judge in a contest sponsored by by the History Channel and the National Inventors Hall of Fame titled "Modern Marvels/Invent Now." A $25,000 prize was awarded to one amoung 25,000 contestants, and the winner was the Enertia House, which was invented by engineer and former log-home architect, Michael Sykes.

The Mother Earth News editor said that these homes had been featured in their magazine before. They essentially provide two wooden shells for the home, one inside the other. She said that there was no mention in the article about the cost per square foot. She was wondering what I thought about the concept from the standpoint of sustainable architecture.

Here is my response:

Double envelope house designs have been around for several decades and they definitely offer some benefits, as well as raise some questions. Any house that takes advantage of the geothermal properties of the ground will be doing its inhabitants and the earth a good turn. This can take the form of earth-sheltering in general, or some clever system of circulating air like the Enertia concept; coupled with sensible passive solar design, it is possible to approach a "zero energy" home.

The concerns about their system that I have are: The use of wood as the primary building material is not generally sustainable in this day of lost forests. With the double envelope design, you are practically building two houses to end up with one. Relying on wood as a thermal mass material compromises the potential thermal performance because wood does not serve this function nearly as well as traditional masonry thermal mass materials. So, I guess what I am saying is that a more sustainable and less costly design can be accomplished in more traditional ways.

Answering the same question, Paul Scheckel wrote, "At first glance, this looks a lot like sunspace design from the 70s (without the stone-filled basement to store heat) which overheated in the daytime and lost lots of heat at night. Consider also that this giant convection oven requires a temperature difference, which in this case is driven by the sun and the cool basement. A New England winter has precious little sun, so my heating system will drive the convective loop, increasing heat loss (in addition to the insulation-free envelope). I haven't heard too many people (ie: none) say that wood is bad for houses and better for biodiesel, but there are good arguments for not using so much material in a home. Does it work? I'd like to see one built in the northeast and see the resulting energy data, wherein the proof will lie."

Clark Snell of www.thinkgreenbuilding.com wrote, "I spent five minutes looking over the web site, so these comments are only based at looking at marketing materials, i.e. they may be inaccurate. Ditto what has been said so far. A couple more “red flags:”

1. Solid wood envelope. They seem to be using the old “mass enhanced R-value” argument for why solid wood walls perform well thermally. I think it’s well established that this is true only in very specific climatic situations. Touting solid southern yellow pine walls in comparison to solid white pine walls is like saying a Chevy Suburban gets better gas mileage than a Hummer…that’s not really a useful statistic.
2. Energy without oil. The presentation intimates that this is a completely passive design. For example, no heating system is mentioned. That simply isn’t credible for most climates using the technology they are describing.
3. Passive means local. You simply can’t create a design that relies heavily on passive techniques and generalize it across climates. In my area where we have high humidity, I’d wonder about this convective loop through the attic and basement, for example.

I could go on. I’m a passive design freak, so I’m all for the basic concepts they are dealing with. However, I don’t see anything really new here, but see marketing claims touting what they are doing as a major breakthrough and “the answer”. That always makes me nervous."

David Eisenberg, of www.dcat.net wrote, "After a skimming around their website, I see that they sell kits and their base prices don't include a lot of things - some of which are enumerated:

The idea of making walls by stacking bags of sand or earth has been around for at least a century. Originally sand bags were used for flood control and military bunkers because they are easy to transport to where they need to be used, fast to assemble, inexpensive, and effective at their task of warding off both water and bullets.

At first natural materials such as burlap were used to manufacture the bags; more recently woven polypropylene has become the preferred material because of its superior strength. The burlap will actually last a bit longer if subjected to sunlight, but it will eventually rot if left damp, whereas polypropylene is unaffected by moisture.

Because of this history of military and flood control, the use of sandbags has generally been associated with the construction of temporary structures or barriers. Using sandbags to actually build houses or permanent structures has been a relatively recent innovation.

It was an Iranian-born architect named Nader Khalili who has popularized the notion of building permanent structures with bags filled with earthen materials. Actually his first concept was to fill the bags with moon dust! Attending a 1984 NASA symposium for brainstorming ways to build shelters on the moon, Khalili coupled the old sandbag idea with the ancient adobe dome and arch construction methods from his homeland in the Middle East. He realized that bags filled with lunar “dirt” could be stacked into domes or vaults to provide shelter.

Khalili came up with a further refinement on this building concept on Earth: for a more permanent, shock-resistant structure, why not place strands of barbed wire between the courses of bags, thus unifying the shell into a more monolithic structure?

At first Khalili was filling his experimental bags with desert sand, but then he evolved his idea of “superadobe,” where bags or long tubes of polypropylene bag material would be filled with a moistened adobe soil that would dry into large adobe blocks. In this case the original bag material was merely the initial form and would not necessarily be an integral part of the eventual structure.

Soon after these first experiments, Khalili began publicizing his work through newspaper and magazine articles and conducting workshops and seminars on the techniques that he was perfecting. Many people who read about his work, visited his compound in Hesperia, California, or studied with him there, decided to go ahead with their own experiments with his ideas.

Among these “early adopters” were Joe Kennedy, Paulina Wojciechowska, Kaki Hunter and Doni Kiffmeyer, Akio Inoue, and Kelly Hart. I believe that it was Joe Kennedy who coined the more general term “earthbag” to suggest that the bag could contain a variety of earthen materials.

Paulina Wojciechowska was the first to write an entire book on the topic of earthbag building: Building with Earth: A Guide to Flexible-Form Earthbag Construction was published in 2001. This featured some of her early experiments done at Khalili’s CalEarth, along with several other case histories.

Akio Inoue, from Tenri University in Japan, has done extensive experimentation with earthbag construction, both on the campus of the University and in India and Africa where many other domes have been built for assistance programs.

Kaki Hunter and Doni Kiffmeyer (a couple) became enamored with earthbag construction after studying with Khalili, and worked on a variety of projects, both for themselves and for clients. In 2004 they wrote and got published another book, Earthbag Building: the Tools, Tricks and Techniques, based on their particular experience.

Kelly Hart (the author of this article) first began experimenting with earthbag building in 1997, after being exposed to the concept while producing his video program, A Sampler of Alternative Homes: Approaching Sustainable Architecture. He later documented his experience in actually building his own home in another program titled Building with Bags: How We Made Our Experimental Earthbag/Papercrete Home. Both of these programs are now available as DVD’s.

In the meantime, Nader Khalili was continuing the promotion of his “Superadobe” technique and eventually decided to patent the idea, which he obtained in the U. S. in 1999, using very general terms that cover using bags made of any material being filled with virtually any material, and combining these with barbed wired between the courses. While having made many public statements that this concept was his gift to humanity, he obviously wanted to capitalize on the potential economic reward.

Many of us who had been engaged in promoting earthbag building on our own were contacted by Khalili and asked to enter into contracts with him in order to continue our work. It didn’t take much research to discover that his patent could easily be disqualified because he had been publicizing his techniques through various media for at least four years before he even applied for his patent. Patent law clearly states that such publicity occurring prior to one year before the patent application would disqualify it for consideration.

So now the door is wide open for anyone to take this concept and run with it, and more people are doing so all the time, all over the world. While Khalili (and most of his students) have focused primarily on using the bags to form large adobe blocks, others have tried filling the bags with a variety of other materials, such as crushed volcanic rock, crushed coral, non-adobe soils, gravel, and rice hulls.

Earthbag building is unique among all other building technologies in that it can be either insulation or thermal mass, depending on what the bags are filled with. This is a very important distinction, because these characteristics of a wall greatly influence how comfortable, economical, and ecological any given system will be.

Safety is of prime concern with all building technologies, and much experimentation and testing has been done to establish guidelines for many ways of building. Khalili has established a relationship with the building department in Hesperia, California where CalEarth is located, an area where earthquakes are naturally a great danger. In 1993 live-load tests to simulate seismic, snow and wind loads were performed on a number of domed earthbag structures at CalEarth and these exceeded code requirements by 200%.

In 1995 dynamic and static load tests were performed on several prototypes for a planned Hesperia Museum and Nature Center to be constructed using Khalili’s Superadobe concepts with both dome and vault shapes. All of these tests exceeded ICBO and City of Hesperia requirements.

In 2006, at the request of Dr. Owen Geiger of the Geiger Research Institute of Sustainable Building, the Department of Civil and Mechanical Engineering of the U.S. Military Academy at West Point conducted several controlled and computer-monitored tests to determine the ability of polypropylene earthbags filled with sand, local soil, and rubble to withstand vertical loads. Their written report concluded that “overall, the earthbags show promise as a low cost building alternative. Very cheap, and easy to construct, they have proven durable under loads that will be seen in a single story residential home. More testing should prove the reliability and usefulness of earthbags.”

Despite the success of these tests, earthbag building concepts have yet to be incorporated into the International Residential Building Code. Obviously more enlightened acceptance of the demonstrated viability of earthbag building needs to occur!

It is difficult to know how many residences and other earthbag structures have been made at this point, probably hundreds if not thousands. Many of us have been promoting the technique for use as emergency shelters, and certainly some have been built for this reason. It is easy for folks to accept this way of building temporary shelters because it fits the historical model of sandbag use.

But many of us have also built substantial homes using earthbags, and in the process realized how truly versatile and sustainable the technique is. I wouldn’t be surprised if many of these earthbag homes are still standing long after their conventional counterparts built contemporaneously have disintegrated.

Chile is exporting a lot more than a mean pisco these days. The XVI Chilean Architecture Biennial, a celebration of great Chilean architecture, recently wrapped this week in Santiago where the main theme was an exploration of architecture that cares for the earth. Hosted at the Contemporary Art Museum of Forestal Park, there was literally too much talent for the conventional structure to contain and the Biennial exploded out into the public eye in form of a completely sustainable, modern temporary pavilion designed by Assadi + Pulido, a young Santiago-based design studio with a modern, edgy and recognizable style.

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Outside of Rio de Janeiro, on a beautiful little beach with amazing blue water, sits a little house with a flowering roof that shades and protects like a big tropical banana leaf. Designed by Mareines + Patalano, the open air abode is meant to encourage interaction and connection between man and nature. With verandas and open spaces in between rooms and no corridors, the tropical beach house is an ideal place for social gatherings and parties. The open layout also takes advantage of trade winds that blow in from the sea, providing natural ventilation and passive cooling.

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I recently received two emailed questions about the seeming lack of attention to green building in urban settings:

"I happened to notice that very little, if not at all, mention of urban dwellings and how small urban homes are practically the greenest you can get when you factor in transportation. Green homes spread out in the country, unless you're living off the earth and have no use for a car, may counteract your carbon footprint savings if you have to drive on a continuous basis. A vast majority of Americans live in a metropolitan area, it would be nice if your information can include an aspect to the benefits of small homes in urban dwellings."

"I am curious about building an earth covered or underground home in the future. Can these houses be built on a small lot within a city? I think being close to your neighbors etc., is one way to help achieve sustainable living, however, the green homes I have seen always appear to be on a large parcel of land."

I think these folks are absolutely right about this. It is unfortunate that most of the natural building movement has been more of a rural activity...but there is no reason why it has to be. Virtually all of the principles of sustainable architecture that I outline at http://greenhomebuilding.com/sustainable_architecture.htm would equally apply in an urban setting.

In districts where housing goes above 2 or 3 stories, it is difficult to use some of the more natural techniques. One problem is that many of these methods of building result in rather thick walls, especially when the walls must go quite high, so that interior space is compromised by this. This is where some hybrid concepts might be useful, such as building with a steel framework to allow multiple stories, and then fill in the walls with less industrial materials, such as strawbales, cordwood, or earthbags.

As for going underground in a city, it certainly can be done. It would be a great way to create dwelling space and reserve most of the land above for gardening or parks, creating much needed green space in the city.

Also much of the movement towards "sharing facilities," such as co-housing, can be done in cities. This is another way to create both denser housing and reserve open space for parks and gardening.

I think that all proponents of green architecture need to put more creative thought into urban design!

I received an email from Professor Sunny Cai, who teaches architectural design at a college in Beijing , China. He mentioned his interest in ancient Chinese architecture, especially the earthen buildings called “tulou,” and he sent me some pictures of these rammed earth buildings.

I had never seen anything quite like them, so I queried him further about how they were made and used. He replied, “The foundation was built with rocks, 2 feet high all around. The juice of glutinous rice and some lime is mixed into the earth for strength, and then sliced bamboo, reeds, and sometimes pieces of wood are also used.”

This picture was taken in front of a rammed earth building with Sunny Cai and his students.

I did some further internet research and found out more about these interesting structures. Tulou are traditional communal residences in the Fujian province of Southern China, often of a circular configuration surrounding a central shrine. Some of these vernacular structures were constructed of cut granite or had substantial walls of fired brick. The end result is a well lit, well-ventilated, windproof, earthquake resistant building that is warm in winter and cool in summer.

There are more than 20,000 tulou in southern Fujian, and these were designated as a UNESCO World Heritage site in 2008 as “exceptional examples of a building tradition and function exemplifying a particular type of communal living and defensive organization, and, in terms of their harmonious relationship with their environment".

Actually the Tulou were built by a minority called the Hakka, who were originally Han who fled south to escape war and famine during the Qin Dynasty (221-206 BC). As they gradually moved they changed the local architecture by incorporating Han styles and that produced the tulou. Not only were the high walls built for defense but they were also the result of traditional Han architecture. Tulou were mostly built between the 12th to the 20th centuries. The oldest one was constructed over 1,200 years ago and is regarded as a “living fossil” of the construction style of central China.

There are three types of Tulou. The Wufeng has three halls and two side rooms and are said to be the result of a redesign of the Han courtyard. The oldest tulou are the rectangle ones, and the most emblematic ones are round. They are typically designed for defensive purposes and consist of one entrance and no windows at ground level. The biggest round one can have up to five stories with three interior rings. The largest houses cover over 40,000 m² and it is not unusual to find surviving houses of over 10,000 m². Most round tulous are three or four stories, with family kitchens and livestock on the ground floor. The next floor becomes a storage room for food and furniture (with no windows), and above that are the bedrooms.

These structures are exemplary of sustainable architecture in that they are built of local, natural materials with simple techniques. They have good thermal attributes, with the massive earthen walls to help buffer temperatures. They are obviously built to last, and house many of the necessities for life. And they embody a communal life style that conserves energy and resources; these represent a form of ancient co-housing.

I attended the Natural Building Colloquium held this year at the Orella Ranch overlooking the Pacific Ocean near Santa Barbara, California, at the end of October. What a magnificent setting this was to spend a fine week of connecting with fellow enthusiasts of the natural building movement. About 70 attendees shared our insights, stories, passions, songs, poetry, cooking, concerns, and labor. I came away with gratitude for the opportunity to interact with such caring people, and with a renewed sense of confidence that we will manage to help forge a sustainable future.

This year’s Colloquium was organized by the Natural Building Network (www.naturalbuildingnetwork.org) and was hosted by Gunner Tautrim, who represents the sixth generation of this family living on this land since 1866. The accommodations were primitive, with only a small kitchen as enclosed space; the rest of the facilities were rustic pit privies, temporary solar shower stalls, temporary bamboo and tarp meeting spaces, and a nice lawn area. We brought tents for sleeping. All of this was happening with the grandeur of the Pacific coast as a backdrop, and the elemental simplicity and beauty combined to create an appropriate mood for contemplating the benefits of building naturally. After breakfast each morning we would gather in a big circle on the lawn to review the various options for the rest of the day and share other thoughts. Typically the mornings were devoted to work on a sturdy, permanent, multi-stalled toilet facility that was already framed with wood. Gunner wanted the walls and a surrounding fence to be finished with natural materials, and there were many volunteers who formed teams to accomplish this. Mostly, split bamboo or recycled fencing was used for a framework, over which cob and clay finishes were applied.

Lunchtime often featured tables where specific discussions would occur, having spontaneously been announced at the morning circle. The afternoons were reserved for many concurrent presentations or discussions, so there were always hard choices to make about what to attend. During the course of the week, over forty different topics were explored, in a variety of meeting places. These ranged from the use of materials (such as bamboo, cob, adobe, and lime) to more theoretical discussions about engineering, thermal properties, efficiency, and design. One of the most popular forums was about codes and ways of improving the acceptance of natural building techniques by building officials. I will be writing about this topic in more detail in a future blog post.

I shared one two-hour presentation about earthbag building around the world with a woman architect from Israel, who had brought plans for an earthbag residence that she was designing for a client there. First I talked about the history and development of this technique, and then profiled a number of projects that have been completed (see www.earthbagbuilding.com). After this introduction, the architect laid her plans on a table and we all discussed specific questions that she had about them. This was a great way to learn some of the basics of earthbag building, and then apply these concepts to a specific situation.
I was very pleased that a discussion was convened to explore the role that natural building can play in what was described as the “long emergency,” or the compounded effects of climate change, peak oil and other resource depletion, population pressures, and financial crises. Without this discussion I would have felt that we were negligent in addressing these most pressing issues. I plan to write another entire blog post about this.

After dinner (which was always delicious and usually vegetarian), we were treated to a variety of programs or entertainment that emanated from our group. Mostly these were slide or Power Point presentations, but one night was devoted to a talent show with lots of music and some stand-up comedy…great fun. I showed lots of pictures I took when in Jeddah, Saudi Arabia a couple of years ago where I had been invited to discuss sustainable architecture with the faculty and students at the King’s University (see www.greenhomebuilding.com/weblog for my essay about the situation there) .

One morning, about half of us opted to attend a tour of historic adobe buildings in the heart of Santa Barbara. The earliest remnants date to the 1780’s when Spain authorized the construction of a presidio and the Santa Barbara Mission. Much of this early adobe construction was toppled during subsequent earthquakes, but recent reconstruction, using stabilized adobes, has returned the area to its original presence. I chatted (in Spanish) with the Guatemalan and Mexican crew who were making new adobe blocks for further repair work. On the return trip to the Orella Ranch, several of us made a detour to the nearby beach to dip our feet in the ocean.

One of the delights of this event was the participation of James from Zimbabwe, Africa. This very engaging fellow brought with him pictures of a lovely little thatched cob circular building that he and some friends had made. He also brought his large thumb piano to serenade us with African ballads. This was a reminder of the deep roots that natural building has from all corners of the world.

All together this week of camping out in this spectacular place and connecting with these dedicated and compassionate souls has left me feeling heartened that we will find ways to overcome the enormous obstacles that lay ahead.

On a very foggy night before we were to disperse the next morning, during our closing ceremony, we arranged ourselves in two large circles that faced each other. We (on the outer circle) were asked to assume the role of addressing our ancestors (on the inner circle) from some indefinite time in the future. When I did this I felt strangely like I was really speaking from the future. I told the young woman who was sitting across from me that I did not blame her for the difficulties that she and subsequent generations had endured. I said that the pattern was innocently established well before she was born. Industrialization was fashioned to improve life, not deteriorate it, and the consequences were not foreseen. And then I told her how much I appreciated the hard work she was doing to address and correct the mistakes of our ancestors. I said that because of the actions of her generation, we in the future were enjoying a simple and healthy life based on ecological balance, and that we owe her and many of her generation our gratitude for all that they did to make this possible. We then stood and embraced, the Future and the Present, for a moment of true compassion.

To see more of my pictures taken at this event go to flickr.com/photos/kellyhart.