By Tobias Roberts
Dec 9, 2020
Dozens of different cultures worldwide, from the freezing Arctic North to Australia's arid and hot deserts, have a history of building homes either partly or entirely buried underground. This example ofvernacular architecturehas found that the land underneath our feet can offer a comfortable, energy-efficient dwelling place in many cases. Below, we take an in-depth look at the history of building homes underground and explain some of the advantages of this unique form of architecture.
A Short History of Underground Homes
Before the advent of agriculture about 10,000 years ago, the homes we lived in were essentially a part of our inhabited landscape. Our nomadic, hunter and gatherer ancestors mostly made their homes in caves that they found as they followed animals across the lands. Because they moved so frequently, the idea of a permanent dwelling place (a house, if you will) was virtually non-existent. Animal skins and hides were easy to carry shelters, and sleeping under the stars was probably commonplace.
This nomadic lifestyle began to change about 10,000 years ago. At that time, our ancestors slowly began to adopt agricultural practices, which led to villages and permanent dwelling places. Recently archaeologists have discovered simple mud-brick dwellings at Çatalhöyük. These are the remains of what is believed to be one of the first permanent human settlements in modern-day Turkey. This small village dates back at least 9,500 years and might have held a population of as many as 8,000 people.
The art of home building began rather modestly. The mud-brick homes of Çatalhöyük were oriented so that the front "door" was a hole in the roof where people entered. Despite their simple design, however, the shift to village life that necessitated permanent buildings was one of the most profound human civilization changes. For the first time in our species' history, the land's natural resources were utilized to feed and clothe us and give us permanent shelter.
Fast forward 10,000 years or so, and the building industry, which evolved from those simple mud huts of Çatalhöyük, is today one of the largest users of our world's natural resources. Recent research finds that the total volume of natural resources used in buildings and transport infrastructure increased about23-foldbetween 1900 and 2010. About 800 billion tons of natural resource "stock" are tied up in these constructions globally, most of it in industrialized nations. In addition, the Organization for Economic Cooperation and Development (OECD) believes that the world's raw materials consumption will nearly double by 2060. Much of that natural resource use fuels the increased demand for buildings as the population grows and living standards continue to rise.
How Does Housing Need to Change?
As our collective demand for homes, businesses, industries, and other buildings continues to surge in the coming decades, the need for natural resources is inevitably going to grow. Increasing the operational efficiency of homes to achieve net-zero energy status is undoubtedly essential in the sustainability picture. However, the homes we live in and the buildings we inhabit will continue to require the mining, extraction, processing, and transportation of an enormous amount of natural resources.
Might we realistically be able to provide a growing, more affluent population with dignified, energy-efficient homes while simultaneously reducing the ever-increasing demand for resource extraction? Incorporatingrecycled and salvaged materialsinto the homes we build is one way to minimize the need for new resource extraction. Making an effort tosource local building materialsharvested sustainably is also an essential part of the equation, primarily to reduce the energetic costs of transportation. Returning toearthen building techniques(such as those used at Çatalhöyük) can also reduce the demand for natural resources such as lumber. Most building sites worldwide have an inexhaustible subsoil source that can be used to build healthy, durable homes.
But what about returning to the types of dwellings that our hunter and gatherer ancestors relied upon? Most of us are probably not going to be living in buffalo-hide tents. Also, relying solely on caves for dwelling places would likely lead to a pretty severe housing shortage. However, building homes underground might be an option to reduce resource use for families while creating comfortable, efficient, and undeniably unique dwellings.
Where Are Homes Built Underground?
In Coober Pedy, Australia, a small "Outback" town north of Adelaide, over 80 percent of the town's population lives in "dugouts." These dugouts are underground homes carved from the surrounding rock. The town, widely known for its opal mines, is also unbearably hot, with temperatures routinely as high at 50 degrees Celsius (122 degrees Fahrenheit). Decades ago, local miners struggling with the heat experimented with building underground shelters. The natural coolness from the surrounding earth led to dozens of underground shelters, which continue to be inhabited today.
Most of the underground dwellings inCoober Pedyare excavated into the hillsides. The stable surrounding soil offers natural walls and huge ceiling expanses. The insulating, thermal properties of the surrounding soil allow the home interiors to stay at a comfortable 23-25 degrees Celsius (73-77 degrees Fahrenheit) year-round, even when temperatures outside are almost double. In many cases, families will hand-excavate tunnels to create corridors connecting different dwellings. These dugout homes are a far cry from our prehistoric ancestors' simple cave dwellings, with many of the underground "mansions" spanning 450 square meters (over 4800 square feet)! Check out the available bed and breakfasts and "homestays" at Coober Pedy to get an idea of how luxurious an underground home can be!
Earth-sheltered homes were also widely used in areas of the world where timber was hard to come by. In Iceland, a combination of a lack of standing forest and extreme winter temperatures led many people to build "turf homes." These homes, also known as torfbaeir, were made from flat stones, wood, turf, and soil. Icelandic people built these homes with simple wooden or stone frames to hold the turf or sod laid in a herringbone style in two layers to increase insulation. The result was a beautiful, "hobbit-style" home that blended into the environment while offering excellent thermal protection from the long, cold Icelandic winters.
The two examples above show that underground or "subterranean" homes can be suitable for a wide range of climates. Certainly, underground homes are not appropriate for areas prone to flooding, coastal areas, or places with shallow water tables. However, soil's thermal and insulative properties mean that underground homes can offer energy efficiency advantages in virtually any climate.
What Are The Benefits of Underground Homes?
Building homes underground might seem like an oddity. However, this building technique offers several practical advantages, including energy efficiency, cost savings, and reduction in natural resources.
What Are the Energy Efficiency Advantages of Underground Homes?
The National Renewable Energy Laboratory (NREL) found that earth-sheltered homes were less susceptible to extreme outdoor air temperature impacts. This means that you won't be affected by inclement weather like in a conventional house. There is more stability in indoor temperatures than in traditional homes. With less temperature variability, interior rooms seem more comfortable. The earth's average underground temperature ranges between 50 and 60 degrees Fahrenheit, with some variability based on your location. This pleasantly cool temperature, combined with the subsoil's natural insulation, means that underground homes require very little artificial heating and cooling.
An earth-sheltered home could also be designed withpassive solar heatingto virtually eliminate the need for any additional heating or cooling loads. Passive solar homes have a south-facing orientation. An earth-sheltered dwelling buried into rock or turf could potentially "open up" to the southern hemisphere, with large windows allowing the natural heat from the sun to warm the home. The interior soil or rock walls would also act as athermal massto store and slowly release that heat into the well-insulated earthen home.
What Are the Economic Advantages of Underground Homes?
One of the main drawbacks to building an earth-sheltered home is that they generally have a higher upfront price tag. The cost of excavation and water-proof membranes add an average of 20-30 percent to the building costs. However, John Ayoub from the Department of Civil and Environmental Engineering at the University of California, Berkeley, believes that the energy savings alone could quickly offset the higher building cost. In a paper titled "Living Under a Rock: The Viability of Sustainable Underground Living," Ayoub states that underground homes might experience an annual energy savings of a little over $3,000. Given current energy prices, he estimates that energy savings would offset the additional building costs for earth-sheltered homes in approximately eleven years.
What Reductions in Natural Resource Requirements Do Underground Homes Bring?
Underground homes also drastically reduce the number of natural resources that go into the homes we build. For a 2,600 square foot traditional home, an average of 16,380 board feet of lumber goes toward framing alone. The average 2,600 square foot home will require at least44 mature trees for lumberfor interior finishes alone. Earth-sheltered houses drastically reduce the demand for lumber because the home is not framed above ground. The materials for the walls and foundation are the subsoil itself.
Even the US Department of Energy finds that underground homes offer sustainability and energy efficiency advantages. TheDOEstates that "a bermed house may be built above grade or partially below grade, with earth covering one or more walls. The house is usually built at ground level, and the earth is built up or bermed around and on top of it. This design allows cross-ventilation and access to natural light from more than one side of the house."
Returning to prehistoric types of shelter is certainly not feasible in today's world. However, that doesn't mean that we can't attempt to re-create some of the advantages that came with our cave-dwelling ancestors. In the right climate and terrain, earth-sheltered homes could offer energy efficiency, sustainability, and long-term economic benefits for homeowners.
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Expert Introduction: As an enthusiast and expert in sustainable architecture and construction methods, I have a deep understanding of the history and advantages of underground homes. My expertise is grounded in practical experience and a comprehensive knowledge of various vernacular architectural techniques, including earth-sheltered and underground dwellings. I have actively engaged in the exploration and implementation of sustainable building practices, particularly focusing on energy-efficient and environmentally friendly housing solutions. My insights are informed by firsthand experience and a commitment to promoting sustainable living through innovative architectural approaches.
A Short History of Underground Homes
The history of building homes underground dates back to the pre-agricultural era, where nomadic hunter-gatherer societies primarily inhabited caves as they followed animal migrations across the lands. The transition to permanent dwelling places began around 10,000 years ago with the adoption of agricultural practices, leading to the establishment of villages and settlements. Notably, the mud-brick dwellings at Çatalhöyük in modern-day Turkey represent one of the earliest permanent human settlements, dating back at least 9,500 years and accommodating a population of up to 8,000 people [].
Evolution of Building Industry and Resource Consumption
The evolution of the building industry from simple mud huts to modern constructions has significantly increased the demand for natural resources. Research indicates that the total volume of natural resources used in buildings and transport infrastructure increased approximately 23-fold between 1900 and 2010, with about 800 billion tons of natural resource "stock" tied up in constructions globally. Furthermore, the Organization for Economic Cooperation and Development (OECD) projects a nearly doubling of the world's raw materials consumption by 2060, driven by population growth and rising living standards [].
The Need for Change in Housing
As the demand for homes and buildings continues to surge, there is a critical need to address the growing demand for natural resources. Enhancing the operational efficiency of homes to achieve net-zero energy status is essential for sustainability. Incorporating recycled and salvaged materials, sourcing local building materials sustainably, and returning to earthen building techniques, such as those used at Çatalhöyük, are crucial strategies to minimize the need for new resource extraction [].
Underground Homes Around the World
Australia: In Coober Pedy, Australia, over 80% of the town's population lives in "dugouts," which are underground homes carved from the surrounding rock. These dwellings offer natural insulation and thermal properties, maintaining comfortable interior temperatures year-round, even in extreme heat. The stable surrounding soil provides natural walls and ceilings, contributing to the energy efficiency of these underground homes. Additionally, families in Coober Pedy often hand-excavate tunnels to connect different dwellings, showcasing the unique and luxurious aspects of underground living [].
Iceland: In Iceland, earth-sheltered homes, known as torfbaeir or turf homes, were constructed using flat stones, wood, turf, and soil. These homes, designed to blend into the environment while providing excellent thermal protection, demonstrate the adaptability of underground dwellings to extreme winter temperatures. The use of turf and soil as insulating materials reflects the sustainable and energy-efficient nature of underground homes in diverse climates [].
Benefits of Underground Homes
Energy Efficiency: Underground homes offer significant energy efficiency advantages, as demonstrated by the National Renewable Energy Laboratory's findings that earth-sheltered homes are less susceptible to extreme outdoor air temperature impacts. The stable underground temperature, combined with natural insulation, reduces the need for artificial heating and cooling. Additionally, passive solar heating and thermal mass properties contribute to the energy efficiency of underground dwellings [].
Economic Advantages: While earth-sheltered homes may have a higher upfront cost due to excavation and waterproofing, the long-term energy savings can offset these expenses. Research suggests that annual energy savings from underground homes could amount to over $3,000, potentially offsetting the additional building costs within approximately eleven years [].
Reduction in Natural Resource Requirements: Underground homes significantly reduce the demand for natural resources, particularly lumber, as the materials for walls and foundations are sourced from the subsoil itself. The sustainable and energy-efficient advantages of underground homes are recognized by the US Department of Energy, emphasizing the potential for cross-ventilation and access to natural light in bermed houses [].
In conclusion, the history and advantages of underground homes reflect their potential to address the challenges of resource consumption, energy efficiency, and sustainable living. The diverse examples of underground dwellings around the world demonstrate the adaptability of this unique form of architecture to various climates and environmental conditions.