As its name suggests, earth sheltering is a means of using earth to effectively shelter an architectural structure, reducing its heat loss and helping to maintain a steady indoor temperature. While it’s seeing a resurgence in popularity as sustainable architecture and passive solar design are being promoted, the practice of earth sheltering has been around for centuries, extending as far back as cave dwellings.
Particularly in regions of extreme temperature and weather conditions, earth sheltered homes are a sustainable housing solution that reduce the need for energy-intensive heating and cooling systems, as well as the detrimental impacts natural disasters can have on conventional housing structures.
History of Earth Sheltering
Throughout history, earth sheltering has been a common building practice across many regions, particularly in the far reaches of the northern hemisphere. Timber framed structures and stone work were often stacked with thick layers of peat against both the walls and roof, insulating and protecting it agains the elements. Over time, these layers of earth grew together and encapsulated the design, blending in with the natural environment. In regions where timber was scarce, stone provided the main means of structural support and in examples like Greenland’s Hvalsey Church you can see where the timber has decomposed, leaving only the stones. Other examples of early earth shelters can be seen in Scotland’s Orkney Islands, with the structures at Skara Brae dating back some 5,000 years.
Today earth shelters generally use large amounts of steel reinforced concrete as a structural support, reducing the sustainability of the building significantly but increasing its longevity. Exceptions do exist however, as seen in Australia’s town of Coober Pedy where the ground is so hard that there is little need for structural support in underground dwellings built to escape the heat.
Types of Earth Shelters
There are basically two different types of earth-sheltered house designs: ‘underground’ which means the entire house is built below grade and ‘bermed’ which is built either above ground or partially below and with earth covering one or more walls.
While an underground earth-sheltered home may sound dark and dingy, an atrium can create an open feeling and light from above, with a central courtyard around which the living spaces are designed. Windows and doors facing the atrium receive sunlight and solar heat, while its below grade design creates significant privacy and protection from wind. For houses being built in noisy areas or built up environments without scenic views, this method of building provides a great alternative.
In bermed earth-sheltered homes, the exposed side of the house should face the sun (south in the northern hemisphere and north in the southern hemisphere), allowing for as much natural light and solar heat as possible. Skylights can increase the daylight that filters into the house and provide much-needed ventilation.
Benefits of Earth Sheltering
Earth sheltering takes advantage of the natural resource of soil as a thermal mass, insulating the structure against the elements and providing energy saving properties. The earth’s mass naturally absorbs heat and retains it, gradually releasing it into its surrounds and (in the case of an earth shelter) the adjacent dwelling. Because of the high density of earth, its change in temperature occurs slowly in what is known as ‘thermal lag’, resulting in a fairly constant temperature compared to the fluctuations experienced in the outside air. As such, earth sheltering takes advantage of passive solar building design, reducing the need for energy-intensive heating and cooling systems. The earthen walls also protect against cold winter winds and limit the escape of warm air through gaps around windows and doors.
Earth shelters are also naturally soundproofed, which can be beneficial in noisy urban areas, and provide greater privacy from neighbors. Earth shelters which sit below the surface also make efficient use of land, with the possibility for lawns or gardens above. In regions prone to high windows and natural disasters such as tornadoes and hurricanes, earth shelters may also cost less to insure as they are less susceptible to catastrophic damage.
Challenges of Earth Sheltering
While there are lots of advantages of building earth sheltered homes, there are also a few challenges involved, with the solid earthen walls of earth shelters often resulting in reduced air circulation and issues with indoor air quality. Creating a healthy air circulation into the design is vital, and what are known as Earthtubes can be used to draw in fresh air, with exhaust vents placed high in the building.
Water seepage can also be an issue in earth sheltered housing, and proper waterproofing needs to be implemented into the design. Non-biodegradable materials are often used in earth sheltering construction to keep water out, including both plastics and energy-intensive concrete, one of the least environmentally sustainable buildings materials available. If earth sheltering is to be implemented as a green building practice in the modern world, more sustainable products will need to be implemented and testing is ongoing in this area.
It’s essential that before constructing an earth sheltered building that the site is carefully surveyed, with aspects such as climate, soil type and water table all impacting significantly on the design and application. The excavation of the site itself is time-consuming and labor intensive, and although it requires less finishing and maintenance than conventional construction methods, the initial costs can be more.
Finding a building company with adequate experience in earth sheltered construction may also be challenging, and taking into account all the dynamic factors involved, this is essential to avoid compromising the end result. Because of the unconventional methods involved, those looking to build an earth shelter can sometimes face challenges during the mortgage application process, and it may take significantly more perseverance to secure the necessary means to build.
Earth Sheltering in Developing Countries
While the use of energy intensive and non-biodegradable materials in its modern application may not make it the most sustainable building option, the historic practice of earth sheltering illustrates that it could be a viable solution throughout the developing world. In areas of extreme temperatures which lack modern heating and cooling appliances, building below the surface and utilizing the thermal mass of the earth could be an affordable alternative.
The low impact design of earth sheltering can work in harmony with the surrounding natural environment and provide a sustainable building method as our green spaces are ever-diminishing. Further research into environmentally friendly structural support is necessary, however, to ensure the energy required to build dwellings is kept at a minimum. As we look towards the future of building and meeting stricter regulations for green homes, it may just be our cave and underground-dwelling ancestors who will provide us with the answers.