Common construction materials such as concrete, steel, wood, masonry, and stone are carbon extensive. Each of the processes of material sourcing, manufacturing, transportation, and end of life, emits GHG emissions.
Generally, locally sourced building materials are more sustainable as they avoid long-haul transportation and thus reduce emissions.
Wood is believed to be one of the most eco friendly materials because it absorbs CO2 and is renewable as long as new trees are planted in place of the harvested trees. Reclaimed wood that is salvaged, treated, and reused has even less negative environmental impact. It reduces construction waste and avoids the use of a new sourced and manufactured building material.
Mud or soil is potentially the most sustainable building material, as it is easily available, can be obtained locally, and reduces waste.
In recent years, Earth-made structures and earth homes builders have gained traction as interest in sustainable building materials has grown. Techniques that use mud/soil as building materials, especially for residential purposes, are adobe, rammed earth, clay bricks, cob, and more.
These techniques claim to provide energy-saving and comfort in different climatic circumstances.
Earth buildings are considered ecological thanks to the thermal inertia properties of clay. Thermal mass absorbs or slows down the passage of heat through a material and then releases that heat when the surrounding ambient temperature decreases. This attribute works best when there is a significant temperature decrease at night and the heat can be released without causing discomfort to occupants.
Earth Architecture is an organization that shares information on the different earth-building techniques and provides a list of books to further delve into each.
The Auroville Earth Institute (AVEI) is a non-profit organization working in 38 countries to promote and disseminate knowledge in the construction of sustainable habitats, specializing in the research, development, promotion, and transfer of earth-based building technologies.
We looked into several earth-construction techniques to explore their climate resilience.
Adobe is mostly a handmade type of construction.
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. A study showed that minimization of transportation needs and the utilization of locally available resources can significantly affect the environmental footprint of an adobe production system.
Adobe is used primarily in dry, mostly warm climates such as in the Southwest U.S, Latin America, the Middle East, and arid parts of Africa and India. Yet, it is believed that adobe homes can be constructed to adapt to cold climates with proper insulation, air barriers, and other techniques. Adobe Homes for All Climates, a book by Lisa Schroder and Vince Ogletree, holds extensive information on the types, benefits, and construction of adobe homes. BuildingGreen Organization provided their insights on the book’s resolution, determining that some information is missing to properly build an adobe home in a cold climate.
Although adobe is believed to be earthquake-resistant, additional measures can help avoid damage from earthquakes. Adobe walls should work jointly with the compatible reinforcements embedded within. This can be obtained by an application of mesh-type reinforcement either internally or externally. Earth Builders in specific seismic zones should adopt thicker walls, better bond beam attachments to the walls, and consistent rational standards for adobe, rammed earth and pressed block.
Adobe's strength and resilience vary with its water content. Too much water weakens the brick. Added asphalt emulsion can help enhance waterproofing properties. A mixture of Portland cement and lime may be added. In parts of Latin America, fermented cactus juice is used for waterproofing.
Generally, adobe buildings deteriorate due to moisture, either excessive rainwater or groundwater. Adobe is resilient if it is well-maintained. Successful stabilization, restoration, and the ultimate survival of an adobe building depend upon how effectively a structure sheds water. The importance of keeping an adobe building free from excessive moisture cannot be overstated.
SuperAdobe is a form of earthbag architecture using sandbags, barbed wire, on-site earth, and a few tools.
This technology has been published by NASA and endorsed by the United Nations.
The sandbags are filled with moistened earth and arranged in layers or long coils. Strands of barbed wire are placed between each layer of sandbag to act as both mortar and reinforcement. Stabilizers such as cement, lime, or asphalt emulsion may be added.
Articles by TKSST and homedit provide further information, including basic instructions for building a superadobe home.
California Institute of Earth Art and Architecture, Cal-Earth, is a nonprofit, which engages in research, development, and education of earth architecture. Located in Hesperia, California, the organization provides resources, hands-on workshops, tours, and open houses.
The sandbags are polypropylene which is waterproof and fireproof. They can also endure heat, wind, and cold.
Note that earthbag housing isn’t suitable for all climates.
The best climate for it is warm and dry with mild temperature swings.
In cold and wet climates, the materials inside the bags will may not dry out, which can cause swelling and heaving. In addition, cold and wet climates promote mildew and mold, which can damage the bags.
3D Printed homes are a growing residential building trend. Large 3D printers print the walls of structures from mostly concrete and similar materials.
An Italian architecture studio and 3D printing company WASP, have collaborated to create the first 3D-printed house made from dirt. Only 200 hours took to complete a 60 square meters (~ 645 square feet) prototype house. Local soil was used in a zero-waste construction process. No building materials had to be transported to the site, avoiding the environmental impact of transportation.
Measuring the environmental impact of 3D printing, we need to consider the transportation of heavy machinery and any materials added to the mix.
While adding concrete has some advantages for durability, earth/dirt can be resilient if treated properly as with the adobe technique.
Research on the climate resilience of 3D printing with dirt is still lacking because it is a new technique. Generally, in 3D printing construction, it’s critical to connect the elements of the house on-site to increase the structure’s resilience, We should expect and explore further research and testing going forward.
Rammed earth walls are constructed by ramming a mix of gravel, sand, silt, and a small amount of clay, into flat panels called formwork and then compressed by a mechanical ram.
Stabilized rammed earth is traditional rammed earth that adds a small amount of cement (typically 5–10%) to increase strength and durability. Stabilized rammed earth walls are usually coated with an air-permeable sealer to extend the life of the material.
Research in New Zealand indicates that earth walls perform better under earthquake conditions than walls made of separate bricks or blocks. Rammed earth is generally very durable. Evidently, many rammed earth buildings have been standing for centuries.
In general, rammed earth has moderate to good moisture resistance. Yet, since rammed earth walls are porous by nature, they have limited insulation properties and need protection from rain and long-term exposure to moisture.
Used correctly, and in the right climate, the thermal mass of rammed earth can delay heat flow through the building envelope by as much as 10-12 hours and moderate daily temperature variations. The thermal mass of rammed earth becomes effective when the difference between day and night outdoor temperatures is at least 6°C.
Rammed earth is not recommended for tropical climates where high-mass construction can hold too much heat and cause thermal discomfort.
Rammed earth is not flammable and has a near 4-hour fire-resistance rating. In addition, the resistance to pests is very high.
Earthships are designed to be able to function independently without the power grid. Earthships are built with natural and repurposed materials ( at least 40 percent recycled material), use thermal or solar heating and cooling, solar and wind energy, harvest and reuse rainwater, have their own contained sewage treatment, and enable owners to grow or produce their food on-site.
The primary Earthship building material is recycled automobile tires filled with compacted earth or compressed soil. Other materials used are recycled aluminum cans, plastic bottles, and cardboard.
The materials are stacked into towers and embedded in cement to create a structure’s foundation.
Earthships originated in the early 1970s by Architect Michael Reynolds but the demand has only started to grow in recent years: about 3,000 structures have been built in 35 states and internationally. Interest is growing partly because people realize they need protection from the changing climate and extreme weather events. In 2022, a beautiful Earthship was listed in New Mexico for close to $3.5M.
In the winter, Earthships utilize the sun rays that enter through the large angled windows and heat the thermal mass in the floors and walls. The heat is naturally released at night when it is needed. In the summer, natural ventilation through buried cooling tubes and vent boxes helps the home stay cool.
Earthships have eco friendly roofing. An Earthship generates its renewable energy using photovoltaic panels, batteries, a charge controller, and an inverter. As a result, an Earthship's electrical needs are about 25% of a conventional home. Earthship homes were also created with water conservation in mind. Each home collects water from rain and snowmelt on the roof, storing it in cisterns which feed a pump and filter system which, in turn, cleans the water and sends it to a solar water heater and pressure tank. From there, water is used for bathing, washing dishes, and laundry. Every drop of water collected from an Earthship roof is used four times.
The structures are designed to be more climate-resilient. The combination of rubber, soil, and concrete makes the Earthship more resistant to storms, earthquakes, and extreme temperatures. Design with fewer corners can help with resistance to strong winds and wildfires. The independence from the energy grid increases the structure's resilience in case of power outages.
The densely earth-packed tires work well in arid, warm climates, such as in Taos, New Mexico, but are likely to fail in humid, rainy climates.
Mold and algae growth may be an issue for Earthship as some dwellers have reported. These issues can cause health concerns and can be costly to repair.
Floods also pose a risk for Earthships as the structures are usually not elevated. To protect Earthships from flooding, choose an elevated location. In addition, the vegetation and landscape around the Earthship should be able to absorb water.
There are two basic types of earth-sheltered house designs: underground and bermed. These homes are not constructed of mud or soil but are surrounded, sometimes almost hidden, by mud, soil, and vegetation.
An earth-sheltered home is less susceptible to the impact of extreme outdoor air temperatures than a conventional house and can maintain a stable indoor temperature.
Studies show that earth-sheltered houses are more cost-effective in climates with significant temperature extremes and low humidity, such as the Rocky Mountains and northern Great Plains. Earth temperatures vary significantly less than air temperatures in these areas, which means the earth can absorb extra heat from the house in hot weather or insulate the house to maintain warmth in cold weather.
Concrete is the most common choice for constructing earth-sheltered buildings because it is strong, durable, and fire-resistant. Concrete masonry units (also called concrete blocks) reinforced with steel bars placed in the core of the masonry can also be used, and generally cost less than cast-in-place concrete.
Earth-sheltered houses can cost less to insure because they offer extra protection against high winds, hailstorms, and natural disasters such as tornadoes and hurricanes.
There is an increased level of care required to avoid moisture issues, during construction and throughout the life of the house.
Similar to regular construction, earth construction methods should fit the climate type and conditions of their location. All techniques work well in certain climates but tend to fail in others.
Constructing earth homes in a climate that doesn’t fit the type of structure is feasible but would need extra insulation, air, and water barriers, and possibly additional materials to the mix. All the mentioned additions complicate the design and increase environmental impact.
Earth or soil is inherently considered an environmentally friendly building material because the emissions in the process of sourcing and manufacturing are minimal. Yet, the environmental impact also constitutes the transportation and disposal of all included building materials and machinery.
A big attribute of earth homes is the thermal mass that can store heat during the day and release it at night when temperatures decrease. This can contribute to the home’s energy efficiency and reduce the need for heating and cooling. Yet, this trait works best in climates with large fluctuations of temperatures between day and night. Note that in some techniques the energy efficiency can also be lacking due to the porous properties of the building materials, which reduce the quality of insulation.
We conclude that proper home construction, including constructing earth homes should be done according to the specific climate of the location, with the help of knowledgeable professionals. Here are some considerations if you desire an earth home:
- What is the climate zone of the property’s location?
- What are the high climate risks in this location? Floods? Wildfires? Extreme heat? Strong winds?
- What natural building materials can be sourced locally?
- Choose an earth home method that fits the climate zone, can withstand the relevant climate risks, and is constructed with local natural building materials.
- Choose knowledgeable professionals to help you with the design and implementation of climate-resilient solutions.
Check out our climate zones blog series to discover key considerations for construction in different U.S climate zones.
To better understand the climate you live in, use our tool to discover the climate zone in your zip code.