What do you mean, made of earth?

It is estimated that between a third and a half of the world's population - approximately three billion people on six continents - lives in buildings constructed of earth. The typologies of earthen architecture, however, extend beyond buildings for living, and include structures for working and worshiping, as well as the countless forms of earthen architecture that are not inhabited by humans, such as agricultural buildings, city walls, and monuments. In India there are estimated to be as many as 80 million dwellings made of earth, and in China the number of people living in earthen homes is estimated to be 100 million. In France 15% of rural buildings are made of rammed earth, and the United States is the leading consumer of mud bricks in the industrialized world.' This makes the ground we walk on and cultivate our crops in the most widely used building material on the planet—that's right, dirt. This does not include, nor should be confused with, other materials that come from the ground, such as stone, cement, or metals derived from ore. Earth, by this definition, is simply clay, gravel, sand, silt, or other friable soils, in which organic materials sometimes exist. Because of the ubiquitous availability of appropriate soil, buildings constructed of earth can also be found just about everywhere in almost every terrestrial biome on the planet.

How can a building be made of earth?

There are perhaps twenty different methods of employing earth to construct walls, floors, and roofs of varying dimension and form. The adaptability of the material has allowed it to respond to a wide range of contexts, cultures, and epochs, including the spectrum of architectural history from antiquity to the modern era. Among those methods are mud brick, which are bricks made of sun-dried mud; rammed earth, which is earth compacted between a formwork until rock hard; cob, which is a mud and straw mixture that is stacked by hand; wattle and daub, which is mud plastered on a lathe; and now, 3D printing, which extrudes a mud mixture through a tube that is guided by a robot until it dries to produce beautiful, sustainable, termite resistant, thermally responsive walls. The walls are structural and can hold a variety of finishes, from natural clay to plasters and stuccos to create clean, elegant surfaces.

Are earthen buildings long lasting?

Earthen buildings are not fragile or temporary. Earth buildings represent the oldest extant buildings on the planet. Using approximately 7,000,000 mud bricks, the Ziggurat at Ur was constructed 6,000 years ago. Taos Pueblo in New Mexico, constructed between 1000 and 1450 C.E., is the oldest continuously occupied dwelling in North America — constructed entirely from raw earth. As with any building, keeping moisture away from the walls is key, and protecting them with a good roof with overhanging eves, as well as a good foundation are all that is necessary. Depending on the exterior finish, even a raw earth finish can list for decades, and the only maintenance required is to simply re-apply earthen plaster, which would be substantially less expensive and less toxic than paints.

Who lives in earthen buildings?

Earth buildings are commonly perceived to be used only by the poor or found only in "developing" countries, but there are earth buildings of almost every architectural type in use by every economic and social class in both the industrialized and non-industrialized worlds. Airports, embassies, hospitals, museums, and factories are just a few examples of the variety of earth building types found throughout the world. For example, the Nk’Mip Desert Cultural Centre in British Columbia has the largest rammed earth wall in North America. Many middle-class and wealthy residents inhabit the vast mud brick suburbs of Santa Fe, New Mexico. Ronald Reagan's Rancho del Cielo, also known as "The Western White House," in California; Saddam Hussein's childhood home in Iraq; the historic home of Paul Revere, also the oldest house in Boston; and Chairman Mao's childhood home in China were all constructed of earth. Several of the buildings housing the minimalist artist Donald Judd's vast and priceless collection at the Judd Foundation in Marfa, Texas, are made of mud brick. Such diversity speaks to the wide spectrum of philosophies, social strata, and cultures represented by this universal material. Today we can find so many beautiful examples of earthen buildings around the world that respond to contemporary ways of life.

Why build with earth?

Earth is an inherently ecological material. The built environment generates 40% of annual global CO2 emissions. Of those total emissions, building operations are responsible for 27% annually, while building and infrastructure materials and construction (typically referred to as embodied carbon) are responsible for an additional 13% annually. Earth produces ZERO carbon dioxide emissions. Earth has excellent thermal mass properties, which can maintain comfortable interior temperatures without the need for mechanical heating and cooling lessening the production of CO2 via the architecture. The utilization of earth requires little embodied energy and structures made of it are highly recyclable. When abandoned, earthen buildings simply melt back into the ground, and their ruins can be used to grow vegetation or be reused again as a building material. The fusion of earth with advanced design and construction is not only a strategy to build sustainably and ecologically — it is also a solution to our global climate challenges.