Earth sheltering - AbsoluteAstronomy.com

Earth sheltering is the architectural practice of using earth

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

against building walls for external thermal mass

Thermal mass

Thermal mass is a concept in building design which describes how the mass of the building provides "inertia" against temperature fluctuations, sometimes known as the thermal flywheel effect...

, to reduce heat loss, and to easily maintain a steady indoor air temperature. Earth sheltering is popular in modern times among advocates of passive solar and sustainable architecture

Sustainable architecture

Sustainable architecture is a general term that describes environmentally conscious design techniques in the field of architecture. Sustainable architecture is framed by the larger discussion of sustainability and the pressing economic and political issues of our world...

, but has been around for nearly as long as humans have been constructing their own shelter.

Background

Living within earth shelters has been a large part of human history.
The connection to earth shelter dwellings began with the utilization of caves, and over time evolving technologies led to the construction of customized earth dwellings. Today, earth shelter construction is a rare practice, especially in the U.S.A. During the energy crisis and the 1973 Oil Crisis

1973 oil crisis

The 1973 oil crisis started in October 1973, when the members of Organization of Arab Petroleum Exporting Countries or the OAPEC proclaimed an oil embargo. This was "in response to the U.S. decision to re-supply the Israeli military" during the Yom Kippur war. It lasted until March 1974. With the...

, along with the back-to-the-land movement, there was a surge of interest in earth shelter/underground home construction in an effort toward self-sufficient living. However, progress has been slow, and earth shelter construction is often viewed by architects, engineers, and the public alike as an unconventional method of building. Techniques of earth sheltering have not yet become common knowledge, and much of society still remains unaware of the process or benefits of this type of building construction.

Types of construction

Earth berming: Earth is piled up against exterior walls and packed, sloping down away from the house. The roof may, or may not be, fully earth covered, and windows/openings may occur on one or more sides of the shelter. Due to the building being above ground, fewer moisture problems are associated with earth berming in comparison to underground/fully recessed construction.
In-hill construction: The house is set into a slope or hillside. The most practical application is using a hill facing towards the equator (south in the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

and north in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

). There is only one exposed wall in this type of earth sheltering, the wall facing out of the hill, all other walls are embedded within the earth/hill.
Underground/fully recessed construction: The ground is excavated, and the house is set in below grade. It can also be referred to as an Atrium
Atrium (architecture)
In modern architecture, an atrium is a large open space, often several stories high and having a glazed roof and/or large windows, often situated within a larger multistory building and often located immediately beyond the main entrance doors...

style due to the common atrium/courtyard constructed in the middle of the shelter to provide adequate light and ventilation.

Benefits

The benefits of earth sheltering are numerous. They include: taking advantage of the earth as a thermal mass, offering extra protection from the natural elements, energy savings, providing substantial privacy, efficient use of land in urban settings, shelters have low maintenance requirements, and earth sheltering commonly takes advantage of passive solar building design

Passive solar building design

In passive solar building design, windows, walls, and floors are made to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer...

.

The Earth's mass absorbs and retains heat. Over time, this heat is released to surrounding areas, such as an earth shelter. Because of the high density of the earth, change in the earth’s temperature occurs slowly. This is known as ‘thermal lag.’ Because of this principle, the earth provides a fairly constant temperature for the underground shelters, even when the outdoor temperature undergoes great fluctuation. In most of the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, the average temperature of the earth once below the frost line

Frost line

The frost line—also known as frost depth or freezing depth—is most commonly the depth to which the groundwater in soil is expected to freeze. The frost depth depends on the climatic conditions of an area, the heat transfer properties of the soil and adjacent materials, and on nearby heat sources...

is between 55 and 57 degrees Fahrenheit (13 to 14 degrees Celsius). Frost line depths vary from region to region. In the USA frost lines can range from roughly 20 inches to more than 40 inches. Thus, at the base of a deep earth berm

Berm

A berm is a level space, shelf, or raised barrier separating two areas. Berm originates in the Middle Dutch and German berme and came into usage in English via French.- History :...

, the house is heated against an exterior temperature gradient of perhaps ten to fifteen degrees, instead of against a steeper temperature grade where air is on the outside of the wall instead of earth. During the summer, the temperature gradient helps to cool the house.

The reduction of air infiltration within an earth shelter can be highly profitable. Because three walls of the structure are mainly surrounded by earth, very little surface area is exposed to the outside air. This alleviates the problem of warm air escaping the house through gaps around windows and door. Furthermore, the earth walls protect against cold winter winds which might otherwise penetrate these gaps. However, this can also become a potential indoor air quality problem. Healthy air circulation is key.

As a result of the increased thermal mass

Thermal mass

Thermal mass is a concept in building design which describes how the mass of the building provides "inertia" against temperature fluctuations, sometimes known as the thermal flywheel effect...

of the structure, the thermal lag

Thermal lag

"'Thermal lag'" describes a material's thermal mass with respect to time. A material with high thermal mass will have a large thermal lag....

of the earth, the protection against unwanted air infiltration and the combined use of passive solar techniques, the need for extra heating and cooling is minimal. Therefore, there is a drastic reduction in energy consumption required for the home compared to homes of typical construction.

Earth shelters also provide privacy from neighbours, as well as soundproofing. The ground provides acoustic protection against outside noise. This can be a major benefit in urban areas or near highways. In urban areas, another benefit of underground sheltering is the efficient use of land. Many houses can sit below grade without spoiling the habitat above ground. Each site can contain both a house and a lawn/garden.

Potential problems

Problems of water seepage, internal condensation

Condensation

Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

, bad acoustics, and poor indoor air quality can occur if an earth shelter has not been properly designed.

Issues also include the sustainability of building materials. Earth sheltering often requires heavier construction than conventional building techniques, and many construction companies have limited or no experience with earth sheltered construction, potentially compromising the physical construction of even the best designs.

The threat of water seepage occurs around areas where the waterproofing layers have been penetrated. Vents and ducts emerging from the roof can cause specific problems due to the possibility of movement. Precast concrete slabs can have a deflection of 1/2 inch or more when the earth/soil is layered on top of it. If the vents or ducts are held rigidly in place during this deflection, the result is usually the failure of the waterproofing layer. To avoid this difficulty, vents can be placed on other sides of the building (besides the roof), or separate segments of pipes can be installed. A narrower pipe in the roof that fits snugly into a larger segment within the building can also be used. The threat of water seepage, condensation, and poor indoor air quality can all be overcome with proper waterproofing and ventilation.

The building materials for earth sheltered construction tend to be of non-biodegradable substances. Because the materials must keep water out, they are often made of plastics. Concrete is another material that is used in great quantity. More sustainable products are being tested to replace the cement

Cement

In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

within concrete (such as fly ash

Fly ash

Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal...

), as well as alternatives to reinforced concrete (see more under Materials: Structural). The excavation of a site is also drastically time- and labor-consuming. Overall, the construction is comparable to conventional construction, because the building requires minimal finishing and significantly less maintenance.

Condensation and poor quality indoor air problems can be solved by using earthtubes, or what is known as a geothermal heat pump - a concept different from earth sheltering. With modification, the idea of earthtubes can be used for underground buildings: instead of looping the earthtubes, leave one end open downslope to draw in fresh air using the chimney effect by having exhaust vents placed high in the underground building.

Landscape and site planning

The site planning

Site planning

Site planning in landscape architecture and architecture refers to the organizational stage of the landscape design process. It involves the organization of land use zoning, access, circulation, privacy, security, shelter, land drainage, and other factors...

for an earth sheltered building is an integral part of the overall design; investigating the landscape of a potential building site is crucial. There are many factors to assess when surveying a site for underground construction. The topography, regional climate, vegetation, water table and soil type

Soil type

In terms of soil texture, soil type usually refers to the different sizes of mineral particles in a particular sample. Soil is made up in part of finely ground rock particles, grouped according to size as sand, silt and clay...

of varying landscapes all play dynamic roles in the design and application of earth shelters.

Topography

On land that is relatively flat, a fully recessed house with an open courtyard is the most appropriate design. On a sloping site, the house is set right into the hill. The slope will determine the location of the window wall; a south facing exposed wall is the most practical in the Northern hemisphere (and north facing in the southern hemisphere) due to solar benefits.

Regional climate

Depending on the region and site selected for earth sheltered construction, the benefits and objectives of the earth shelter construction vary. For cool and temperate climates, objectives consist of retaining winter heat, avoiding infiltration, receiving winter sun, using thermal mass, shading and ventilating during the summer, and avoiding winter winds and cold pockets. For hot, arid climates objectives include maximizing humidity, providing summer shade, maximizing summer air movement, and retaining winter heat. For hot, humid climates objective include avoiding summer humidity, providing summer ventilation, and retaining winter heat.

Regions with extreme daily and seasonal temperatures emphasize the value of earth as a thermal mass. In this way, earth sheltering is most effective in regions with high cooling and heating needs, and high temperature differentials. In regions such as the south eastern United States, earth sheltering may need additional care in maintenance and construction due to condensation problems in regard to the high humidity. The ground temperature of the region may be too high to permit earth cooling if temperatures fluctuate only slightly from day to night. Preferably, there should be adequate winter solar radiation, and sufficient means for natural ventilation. Wind is a critical aspect to evaluate during site planning, for reasons regarding wind chill and heat loss, as well as ventilation of the shelter. In the Northern Hemisphere, south facing slopes tend to avoid cold winter winds typically blown in from the north. Fully recessed shelters also offer adequate protection against these harsh winds. However, atria within the structure have the ability to cause minor turbulence depending on the size. In the summer, it is helpful to take advantage of the prevailing winds. Because of the limited window arrangement in most earth shelters, and the resistance to air infiltration, the air within a structure can become stagnant if proper ventilation is not provided. By making use of the wind, natural ventilation can occur without the use of fans or other active systems. Knowing the direction, and intensity, of seasonal winds is vital in promoting cross ventilation. Vents are commonly placed in the roof of bermed or fully recessed shelters to achieve this effect.

Vegetation

The plant cover of the landscape is another important factor. Adding plants can be both positive and negative. Nearby trees may be valuable in wet climates because their roots remove water. However a prospective builder should know what types of trees are in the area and how large and rapidly they tend to grow, due to possible solar-potential compromise with their growth. Vegetation can provide a windbreak for houses exposed to winter winds. The growth of small vegetation, especially those with deep roots, also helps in the prevention of erosion, on the house and in the surrounding site.

Soil and drainage

The soil type is one of the most essential factors during site planning. The soil needs to provide adequate bearing capacity

Bearing capacity

In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil...

and drainage

Drainage

Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...

, and help to retain heat. With respects to drainage, the most suitable type of soil for earth sheltering is a mixture of sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

and gravel

Gravel

Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

. Well graded gravels have a large bearing capacity (about 8,000 pounds per square foot), excellent drainage and a low frost heave

Frost heaving

Frost heaving results from ice forming beneath the surface of soil during freezing conditions in the atmosphere. The ice grows in the direction of heat loss , starting at the freezing front or boundary in the soil...

potential. Sand and clay

Clay

Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

can be susceptible to erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

. Clay soils, while least susceptible to erosion, often do not allow for proper drainage, and have a higher potential for frost heaves. Clay soils are more susceptible to thermal shrinking and expanding. Being aware of the moisture content of the soil and the fluctuation of that content throughout the year will help prevent potential heating problems. Frost heaves can also be problematic in some soil. Fine grain soils retain moisture the best and are most susceptible to heaving. A few ways to protect against capillary action

Capillary action

Capillary action, or capilarity, is the ability of a liquid to flow against gravity where liquid spontanously rise in a narrow space such as between the hair of a paint-brush, in a thin tube, or in porous material such as paper or in some non-porous material such as liquified carbon fiber, or in a...

responsible for frost heaves are placing foundations below the freezing zone or insulating ground surface around shallow footings, replacement of frost sensitive soils with granular material, and interrupting capillary draw of moisture by putting a drainage layer of coarser material in the existing soil.

Water can cause potential damage to earth shelters if it ponds around the shelter. Avoiding sites with a high water table

Water table

The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...

is crucial. Drainage, both surface and subsurface, must be properly dealt with. Waterproofing applied to the building is essential.

Atrium designs have an increased risk of flooding, so the surrounding land should slope away from the structure on all sides. A drain pipe at the perimeter of the roof edge can help collect and remove additional water. For bermed homes, an interceptor drain at the crest of the berm along the edge of the roof top is recommended. An interceptor drainage swale

Swale (geographical feature)

A swale is a low tract of land, especially one that is moist or marshy. The term can refer to a natural landscape feature or a human-created one...

in the middle of the berm is also helpful or the back of the berm can be terraced with retaining walls. On sloping sites runoff may cause problems. A drainage swale or gully can be built to divert water around the house, or a gravel filled trench with a drain tile can be installed along with footing drains.

Soil stability should also be considered, especially when evaluating a sloping site. These slopes may be inherently stable when left alone, but cutting into them can greatly compromise their structural stability. Retaining walls and backfills may have to be constructed to hold up the slope prior to shelter construction.

Current methods

In earth sheltered construction there is often extensive excavation done on the building site. An excavation several feet larger than the walls' planned perimeter is made to allow for access to the outside of the wall for waterproofing and insulation. Once the site is prepared and the utility lines installed, a foundation of reinforced concrete is poured. The walls are then installed. Usually they are either poured in place or formed either on or off site and then moved into place. Reinforced concrete is the most common choice. The process is repeated for the roof structure. If the walls, floor and roof are all to be poured in place, it is possible to make them with a single pour. This can reduce the likelihood of there being cracks or leaks at the joints where the concrete has cured at different times.

On the outside of the concrete a waterproofing system is applied. The most frequently used waterproofing system includes a layer of liquid asphalt onto which a heavy grade waterproof membrane is affixed, followed by a final liquid water sealant which may be sprayed on. It is very important to make sure that all of the seams are carefully sealed. It is very difficult to locate and repair leaks in the waterproofing system after the building is completed.

One or more layers of insulation board or foam are added on the outside of the waterproofing. If the insulation chosen is porous, a top layer of waterproofing is added. After everything is complete, earth is backfilled into the remaining space at the exterior of the wall and sometimes over the roof to accommodate a green roof. Any exposed walls and the interior are finished according to the owners' preferences.

Structural

Reinforced concrete is the most commonly used structural material in earth shelter construction. It is strong and readily available. Untreated wood rots within five years of use in earth shelter construction. Steel can be used, but needs to be encased by concrete to keep it from direct contact with the soil which corrodes the metal. Bricks and CMUs (concrete masonry units) are also possible options in earth shelter construction but must be reinforced to keep them from shifting under vertical pressure unless the building is constructed with arches and vaults.

Unfortunately, reinforced concrete is not the most environmentally sustainable material. The concrete industry is working to develop products that are more earth-friendly in response to consumer demands. Products like Grancrete and Hycrete

Hycrete

Hycrete is a concrete addition based on water that is used to counter rust and corrosion. It was developed by the eponymous American company Hycrete and is certified as a Cradle to Cradle nutrient...

are becoming more readily available. They claim to be environmentally friendly and either reduce or eliminate the need for additional waterproofing. However, these are new products and have not been extensively used in earth shelter construction yet.

Some unconventional approaches are also proposed. One such method is a PSP method proposed by Mike Oehler. The PSP method uses wooden posts, plastic sheeting and non-conventional ideas that allow more windows and ventilation. This design also reduces some runoff problems associated with conventional designs. The method uses wood posts, a frame that acts like a rib to distribute settling forces, specific construction methods which rely on fewer pieces of heavy equipment, plastic sheeting, and earth floors with plastic and carpeting.

Waterproofing

Several layers are used for waterproofing in earth shelter construction. The first layer is meant to seal any cracks or pores in the structural materials, also working as an adhesive for the waterproof membrane. The membrane layer is often a thick flexible polyethylene sheeting called EPDM

EPDM rubber

EPDM rubber , a type of synthetic rubber, is an elastomer which is characterized by a wide range of applications. The E refers to ethylene, P to propylene, D to diene and M refers to its classification in ASTM standard D-1418. The M class includes rubbers having a saturated chain of the...

. EPDM is the material usually used in water garden, pond and swimming pool construction. This material also prevents roots from burrowing through the waterproofing. EPDM is very heavy to work with, and can be chewed through by some common insects like fire ants. It is also made from petrochemicals, making it less than perfect environmentally.

There are various cementitious coatings that can be used as waterproofing. The product is sprayed directly onto the unprotected surface. It dries and acts like a huge ceramic layer between the wall and earth. The challenge with this method is, if the wall or foundation shifts in any way, it cracks and water is able to penetrate through it easily.

Bituthene (Registered name) is very similar to the three coat layering process only in one step. It comes already layered in sheets and has a self adhesive backing. The challenge with this is the same as with the manual layering method, in addition it is sun sensitive and must be covered very soon after application.

Eco-Flex is an environmentally friendly waterproofing membrane that seems to work very well on foundations, but not much is known about its effectiveness in earth sheltering. It is among a group of liquid paint-on waterproofing products. The main challenges with these are they must be carefully applied, making sure that every area is covered to the right thickness, and that every crack or gap is tightly sealed.

Bentonite

Bentonite

Bentonite is an absorbent aluminium phyllosilicate, essentially impure clay consisting mostly of montmorillonite. There are different types of bentonite, each named after the respective dominant element, such as potassium , sodium , calcium , and aluminum . Experts debate a number of nomenclatorial...

clay is the alternative that is closest to optimum on the environmental scale. It is naturally occurring and self-healing. The drawback to this system is that it is very heavy and difficult for the owner/builder to install.

Insulation

Unlike conventional building, earth shelters require the insulation on the exterior of the building rather than inside the wall. One reason for this is that it provides protection for the waterproof membrane against freeze damage, another is that the earth shelter is able to better retain its desired temperature. There are two types of insulation used in earth shelter construction. The first is close-celled extruded polystyrene sheets. Two to three inches glued to the outside of the waterproofing is generally sufficient. The second type of insulation is a spray on foam. This works very well where the shape of the structure is unconventional, rounded or difficult to get to. Foam insulation requires an additional protective top coat such as foil to help it resist water penetration.

In some low budget earth shelters, insulation may not be applied to the walls. These methods rely on the U factor or thermal heat storage capacity of the earth itself below the frost layer. These designs are the exception however and risk frost heave damage in colder climates. The theory behind no insulation designs relies on using the thermal mass of the earth to store heat, rather than relying on a heavy masonry or cement inner structures that exist in a typical passive solar house. This is the exception to the rule and cold temperatures may extend down into the earth above the frost line making insulation necessary for higher efficiencies.

Design for energy conservation

Earth sheltered homes are often constructed with energy conservation and savings in mind. Specific designs of earth shelters allow for maximum savings. For bermed or in-hill construction, a common plan is to place all the living spaces on the side of the house facing the equator. This provides maximum solar radiation to bedrooms, living rooms, and kitchen spaces. Rooms that do not require natural daylight and extensive heating such as the bathroom, storage and utility room are typically located on the opposite (or in hill) side of the shelter. This type of layout can also be transposed to a double level house design with both levels completely underground. This plan has the highest energy efficiency of earth sheltered homes because of the compact configuration as well as the structure being submerged deeper in the earth. This provides it with a greater ratio of earth cover to exposed wall than a one story shelter would.

With an atrium earth shelter the living spaces are concentrated around the atrium. The atrium arrangement provides a much less compact plan than that of the one or two story bermed/inhill design; therefore it is commonly less energy efficient, in terms of heating needs. This is one of the reasons why atrium designs are classically applied to warmer climates. However, the atrium does tend to trap air within it which is then heated by the sun and helps reduce heat loss.

Earth sheltering with solar heating

Earth sheltering is often combined with solar heating systems. Most commonly, the utilization of passive solar design techniques is used in earth shelters. A south facing structure with the north, east, and west sides covered with earth, is the most effective application for passive solar systems. A large double glazed window, triple glazed or Zomeworks beadwall (vacuum/blower pumps that filled your double pane solar windows with styrofoam balls at night for extra insulation and vacuumed the beads out in the morning, patent now expired), spanning most of the length of the south wall is critical for solar heat gain. It is helpful to accompany the window with insulated drapes to protect against heat loss at night. Also, during the summer months, providing an overhang, or some sort of shading device, is useful to block out excess solar gain. Combining solar heating with earth sheltering is referred to as "annualized geo solar

Annualized geo solar

Annualized Geo-Solar enables passive solar heating in even cold, foggy north temperate areas. It uses the ground under or around a building as thermal mass to heat and cool the building. After a designed, conductive thermal lag of 6 months the heat is returned to, or removed from, the inhabited...

design", "Passive annual heat storage", or sometimes as an "Umbrella house." (See Nick Pine's posting on usenet alt.homepower and alt.solar.thermal groups about this type of house.) In the umbrella house, Polystyrene insulation extends around 23 feet (7 m) radius from underground walls. A plastic film covers the insulation (for waterproofing), and soil is layer on top. The materials slope downward, like an umbrella. It sheds excess water while keeping the soil temperature warm and dry.

Passive cooling

Passive cooling

Passive cooling refers to technologies or design features used to cool buildings without power consumption, such as those technologies discussed in the Passive house project.-Passive cooling:...

which pulls air with a fan or convection from a near constant temperature air into buried Earth cooling tubes

Earth cooling tubes

A ground-coupled heat exchanger is an underground heat exchanger loop that can capture or dissipate heat to or from the ground. They use the Earth's near constant subterranean temperature to warm or cool air or other fluids for residential, agricultural or industrial uses...

and then into the house living space. This also provides fresh air to occupants and the air exchange required by ASHRAE.

Berming

Historically, earth berming was a common building practice that combined heavy timber framing and rough stone work with stacking thick layers of sod or peat against the walls and on the roof. This served as excellent protection from the elements. In a relatively short period of time the earth layers grow together leaving the structure with an appearance of a hill with a door.

In these early structures, the heavy timber framing acted as structural support and added comfort and warmth to the interior. Rough stone was often stacked along the outer walls with a simple lime mortar for structural support and often serves as an exterior facing wall and foundation. There is a greater use of stone work in earth shelter structures in areas where timber is scarce. These are the most sustainable of the earth shelters as far as materials go because they are able to decompose and return to earth. This is why there are few remaining example like Hvalsey Church in Greenland where only the stacked stones remain. One of the oldest examples of berming, dating back some 5,000 years, can be found at Skara Brae

Skara Brae

Skara Brae is a large stone-built Neolithic settlement, located on the Bay of Skaill on the west coast of Mainland, Orkney, Scotland. It consists of ten clustered houses, and was occupied from roughly 3180 BCE–2500 BCE...

in the Orkney Islands

Orkney Islands

Orkney also known as the Orkney Islands , is an archipelago in northern Scotland, situated north of the coast of Caithness...

off northern Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

.

Today’s bermed earth structures are built quite differently from those of the past. Common construction employs large amounts of steel reinforced concrete acting as structural support and building shell. Bulldozers or bobcats are used to pile earth around the building and on the roof instead of stacking earth in place. A community of 5 bermed earth structures can be found in Hockerton

Hockerton

Hockerton is a village in Nottinghamshire. It is 2 miles from the town of Southwell on the A617 between Newark and Mansfield. Fewer than 60 houses are situated around the church, the Spread Eagle pub and village hall...

in Nottinghamshire

Nottinghamshire

Nottinghamshire is a county in the East Midlands of England, bordering South Yorkshire to the north-west, Lincolnshire to the east, Leicestershire to the south, and Derbyshire to the west...

,UK.

In-hill

One historical example of in-hill earth shelters would be Mesa Verde, in the southwest United States. These building are constructed directly onto the ledges and caves on the face of the cliffs. The front wall is built up with local stone and earth to enclose the structure. Similarly today, in-hill earth shelter construction utilizes the natural formation of a hillside for two to three of the exterior walls and sometimes the roof of a structure. Alternative builders craft a type of in-hill structure known as an Earthship

Earthship

An earthship is a type of passive solar house made of natural and recycled materials. Designed and marketed by Earthship Biotecture of Taos, New Mexico, the homes are primarily constructed to work as autonomous buildings and are generally made of earth-filled tires, using thermal mass...

. In Earthship construction, tires rammed with earth are used as structural materials for three of the walls and generally have a front façade of windows to capture passive solar energy.

The most famous and probably the largest earth-sheltered home is the residence of Bill Gates

Bill Gates' house

Bill Gates' house is a large mansion in the side of a hill overlooking Lake Washington in Medina, Washington. The house is noted for its design and the technology it incorporates...

, who had it built over a period of several years on a heavily wooded site on the shore of Lake Washington

Lake Washington

Lake Washington is a large freshwater lake adjacent to the city of Seattle. It is the largest lake in King County and the second largest in the state of Washington, after Lake Chelan. It is bordered by the cities of Seattle on the west, Bellevue and Kirkland on the east, Renton on the south and...

. It is an excellent example of the lack of obtrusiveness of this kind of home, since it appears much smaller than it actually is, when seen from the lake.

Underground

Though underground construction is relatively uncommon in the US, successful examples can be found in Australia where the ground is so hard that there is little to no need for structural supports and a pick ax and shovel are the tools of the builder/remodeler. See Coober Pedy and Lightning Ridge. The Forestiere Underground Gardens

Forestiere Underground Gardens

Forestiere Underground Gardens Located at 5021 West Shaw Avenue in Fresno, California are an unusual manmade creation built by Baldasare Forestiere, an immigrant from Sicily, over a period of 40 years from 1906 to until his death in 1946. The gardens, while subterranean, have many skylights and...

in Fresno, California is a North American example.

In the early 1970s, China undertook the construction of Dixia Cheng

Underground City (Beijing)

The Underground City , also known as Dixia Cheng, is a bomb shelter comprising a network of tunnels located beneath Beijing, China, which has since been transformed into a tourist attraction. It has been called the Underground Great Wall because it was built for the purpose of military defense...

, a city underneath Beijing

Beijing

Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...

. It was primarily a complex of bomb shelters that could house 40% of the population at that time. It was a response to the fear of Soviet attack. Parts of it are now used in more commercial ventures.

External links

British Earth Sheltering Association
Earth Sheltered Structures: A Pathfinder and Annotated Bibliography
Eco-Flex Rubber - Eco-Flex is a water based, solvent free, non flammable, liquid waterproofing membrane.
Formworks Building Inc. - Designer of contemporary earth-sheltered homes.
Grancrete - Grancrete claims to be a green product that is stronger than concrete, is water and fire resistant and sets up quickly.
Hockerton Housing Project - Community of 5 earth sheltered homes near Nottingham, UK
Hycrete Technologies - Hycrete admixture has the highest “cradle to cradle” rating for sustainability.
StocktonUnderground : An Owner-Builder Approach
Home Sweet Earth Home - Designers and builders of earth sheltered homes

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