Are Adobe Houses Sustainable?

The adobe-building process uses compressed earth to build low-energy, fireproof, biodegradable structures that last many years if constructed correctly. It is an ancient construction method, with its earliest uses dating back to 8300 BC.

Adobe became very popular in arid and semiarid communities where wood was and still is scarce. Just under a third of the global population still uses earthen structures today, especially in developing countries. The resulting houses are not only sustainable because the materials are locally abundant; they are also very energy-efficient buildings.

Adobe House Materials

Adobe houses are traditionally built on a solid foundation, constructed from stone, cement, or even seashells. Builders then erect adobe walls by stacking earthen bricks on top of each other. 

An adobe brick is composed of compacted soil with a small clay consistency. The ideal soil is usually found just below the ground’s top layer and becomes molded together with a little water.

A small amount of dry material, such as straw or grass, is used as a binding agent; too much or too little can reduce the strength of the adobe structure. The dry materials counteract the cracking that occurs in the brick as it dries and shrinks. The amount of water in the brick should be precise, as well. Too much can make the adobe unstable.

The mixture, usually hand-blended, is then placed in a wooden form and leveled off. Taking the shape of the form’s mold, the bricks are removed and placed on a level surface to dry for several days, followed by several weeks of air-curing. The resulting adobe bricks never get fired in a kiln and thus never become waterproof. But the essential moisture in the adobe bricks gives them enough plasticity to join together. 

Building the Walls and Floor

To support the roof’s weight, the adobe walls must be thick. Walls are built by stacking the adobe bricks, similar to conventional masonic bricks, using earth-based or lime mortars to bind together and decrease shrinkage. One study confirmed the thermal stability in adobe walls 50-cm thick, which is considered the standard width of earthen homes in Cyprus where adobe dates back to the Neolithic era. 

The flooring of an adobe house is similar to a modern home. Hardwood, flagstone, and tile are options, as well as adobe or fired brick.

Historically, in dry environments where wood was scarce and adobe popular, vaulted or domed brick roofs were used. In southwestern North America in the 17th century, slightly sloped flat roofs with parapet walls were customary, built using logs covered with twigs or fabric and then adobe mud. In the 19th and 20th centuries, gable and hipped roofs became popular and, later, terra cotta and sheet metal. 

Adobe House Maintenance

Mud plaster is applied to the exterior of the adobe house for additional protection from the elements. This consists of a mix of clay, sand, water, and a dry material. As unfired earthen bricks are not waterproof, an enduring adobe home requires periodic maintenance.

Adobe roofs and walls are prone to damage over time, usually due to water-related problems. More structural damage can occur if the adobe house was built incorrectly. Deterioration or damages can be repaired by patching or replacing the compromised adobe with new brick of as similar an adobe mixture as possible. 

Environmental Benefits

Due to its earthen makeup, adobe walls have a high thermal mass and are able to absorb heat throughout the day to keep the house cool while the sun is up, releasing the heat slowly at night to warm the interior. This process keeps energy consumption low in hot, dry environments.

One study described the thermal inertia of adobe walls as the main contributor to the delay of heat transmission. The thermal mass of adobe ensures that the interior of the home remains relatively stable, slowing the changes during extremely cold or hot exterior temperatures. However, research has shown adobe blocks do not insulate well in colder climates.

The natural material used in adobe significantly lowers the net energy consumption and waste production of the structure. Compared to modern building materials, adobe bricks produce minimal total waste and zero hazardous waste. In the entire cycle of an adobe house’s life, the footprint on the environment is small. When materials are harvested from the local environment, transportation energy decreases significantly.

Other benefits to adobe include low sound transmission and the ability for homeowners to have an integral role in building their home due to the method’s simplicity. Moreover, an adobe house is very customizable in terms of design, and expensive construction equipment is minimized.

While adobe has regained popularity in recent years as a conservation method for and sustainable alternative to traditional homes, it also presents obstacles. Location should be taken into account when considering this building method, as well as the upkeep required to ensure the adobe home remains in stable condition for the future.

Its environmental efficiencies, however, make adobe a good building option for those living in dry climates.