With a long list of benefits, compressed earth blocks make an ideal natural building material.
Approximately one-quarter of the world’s population live in homes made of earth, mostly in the developing world. It makes sense, after all. The dirt’s either cheap or free and the homes have plenty of benefits, including:
being locally sourced
having high thermal mass
having low embodied energy
being highly breathable
being non-toxic, and
being fire-, hurricane-, earthquake-, and tornado-resistant.
However, builders in the West have not embraced earthen construction the way that the developing world has and for one main reason — cost. The dirt may be cheap, but the labor’s not, which is why mechanization makes so much sense to the homebuilder interested in practical sustainability. Compressed earth block (CEB) is a proven technology that makes earthen construction competitive with conventional building.
According to The Art of Natural Building, cob houses were being built in England in the 13th century and cob was a prominent building form, until industrialization and cheap transportation in the late 1800s ushered in modern building techniques. Cob is generally made of a clay-based subsoil mixed with straw, sand, and water. This mixture is then shoveled onto a stone foundation and trodden into place to create a course, or lift, of cob, which would then be left to dry before the wall was added onto, allowing builders great flexibility in design and architecture.
Although earth was the original green building material (or, rather, brown building material), it has never gained popularity in a U.S. building market accustomed to speed and cost-efficiency. Concrete or bricks are human-engineered for building purposes – earth isn’t. Most forms of earthen construction, such as adobe and cob building, are labor-intensive, an approach that can work well for the developing world due to low labor costs but not for a country such as the United States. Considering the relatively low cost and ease of transportation of other available building products, earth generally fails to prove its financial feasibility.
Compressed earth blocks
Compressed earth block construction, however, is one economically viable option that can compete with conventional homebuilding methods. Using the latest mechanical compression technologies, homes can be constructed at an even lower cost than with bricks and wood because the earth blocks can be produced at the rate of 500 or more per hour.
One company making earth building affordable is Advanced Earthen Construction Technologies (AECT), a CEB-machine manufacturer in San Antonio, Texas. They say that, by using their technology to produce bricks, you can build a small rectangular home for about 90% of what it costs to build a brick-and-stick home. “We’ve done homes that were $76 a square foot all the way up to $300 a square foot, depending on the amenities that were put into the homes,” says Lawrence Jetter, president of AECT. Accounting for the great variation in cost, he explains, “What happens with adobe [CEB] is that people start thinking about arches and all that kind of stuff. In those cases, suddenly their plain little home becomes a custom home.” One of earthen construction’s benefits — its design flexibility — can prove to be a major pitfall for the homeowner who possesses a creative urge but lacks financial restraint.
Benefits of building with earth
Jetter admits that it is possible to build a conventional home cheaper than one constructed with earth block, but the question then becomes about quality. “You can go out and use particle board and siding and build one cheaper than the earth block, but in 10 years it’s going to be a piece of junk,” Jetter says. “The cost of owning an earth block home is so much less. One homeowner here had a 3,000 square foot house with an electrical bill of $320 to $340 a month in the summertime. His new [earth] home is 5,700 square feet and it’s $100 to $145 in the summertime because earth blocks are so much more efficient.”
Considering that the earth block house was double the size, that example illustrates the significant cost-savings possible with earthen construction. However, it also suggests another potential pitfall. Like the tendency to overeat when consuming low-fat or sugar-free foods, yielding to the temptation to super-size a home when building with earth sometimes defeats the purpose of building sustainably.
For Dan Powell of Earth Tek Inc., a CEB-machine manufacturer in New Mexico, sustainability is the number one benefit of compressed earth blocks. “They [earth homes] are cooler in the summer and warmer in the winter,” Powell says. “In my experience, in the summertime when it’s 100 degrees outside, you’re walking into a house that’s 65 or 70 degrees.” That kind of cooling efficiency comes from an earth home with a wall thickness of 12" or more, assuming that the doors and windows are closed, making for a home that’s not just energy-efficient but comfortable, since the cooling comes naturally rather than from air conditioning.
Because compressed earth blocks are made from soil, the main building material is locally sourced, a point Powell says is highly empowering for people since they can mine it themselves. Another big benefit for him is the flexibility of working with CEBs. “They're extremely adaptable to nice, complex designs. They’re load-bearing so you can do whatever you want to the walls, with some limitations,” Powell says. In other words, they are a creative builder’s dream.
Auroville Earth Institute researches, develops, and trains people on earth-based technologies. They operate out of India, a country that gets hit hard by all sorts of natural disasters, from earthquakes to tsunamis to cyclones. Their research has found that, although a building’s quality of construction is the major determining factor in whether it will stand after an earthquake, adobe buildings have survived major earthquakes quite well while nearby stone buildings were reduced to rubble. This research has led governments, both inside and outside India, to approve the Auroville Earth Institute’s earthen construction technology for rebuilding efforts in disaster-prone areas.
Earth homes are not just disaster-resistant but durable. According to the Auroville Earth Institute, the Ramesseum in Thebes, Egypt is the oldest standing earthen building at 3,300 years old. And it isn’t alone. All around the world, it’s common to see old earthen buildings still standing when their newer counterparts have long since crumbled to the ground. A long-lasting home is a sustainable home because it needs fewer repairs and less incentive to demolish it and build anew.
So why isn’t everyone building with compressed earth blocks?
“Because no one knows how to do it,” Jetter says. “The architects and engineers don’t know a damn thing about this. They don’t. And it’s not their fault; they weren’t taught.” Earth block construction is still a relatively new thing in modern home building, so the education system has been slow to respond. Jetter is hopeful, though, since a few universities, such as the University of Colorado, Texas A&M University, and the University of Oklahoma are now teaching earth block construction.
Powell points to broken coding and advertising systems in the United States. “Our coding and advertising systems have been geared specifically for lumber and concrete,” he says. “And the lumber and concrete industries are so big that they’ve done their best to make earth block a non-player in the deal.”
With the list of challenges almost as long as the list of benefits, it's no wonder that earthen construction has had a hard time taking off in the developed world. With compressed earth block technology, the main challenge — price — ceases to be an issue, making CEB a viable option for the homebuilder interested in working with a highly sustainable material and for the homeowner wanting an all-around sustainable, comfortable, durable home at an affordable price.