Underground Construction

Underground construction has been around for thousands of years, mostly developed through mining and more recently through transport, housing and commercial industries. The Channel Tunnel, London Underground, British Library, and various shopping centres are all examples of underground construction.

Underground housing (sometimes called earth sheltered housing) refers specifically to homes that have been built underground, either partially or completely. These subterranean homes have grown increasingly popular over the last thirty years and are an important sector in the green building movement.

Thousands of people in Europe and America live in underground homes. In Russia there is more development below the ground than above it. Countries like Japan and China, where development space is at a premium, are particularly keen to build underground living places. In the UK, the movement is much slower, with less than a hundred underground homes in existence. This is partly due to a misinformed belief that underground homes are dirty, damp, dark, claustrophobic and unstable places to live. But it is also due to a lack of guidance and information about building regulations and specifications, and a lack of knowledge about their potential as a sustainable building practice.

Underground Dwelling Design

To a certain extent the design of an underground home is determined by the conditions of the site. Soil type, topography, precipitation, ground water levels, load-bearing properties, and slope stability all need to be carefully considered. Construction materials need to be waterproof, durable and strong enough to withstand underground pressure (concrete is frequently used). Water is a particular consideration in underground building, and special drainage techniques may need to be implemented around the site, particularly along the roof areas.

There are several methods of building for subterranean living:

• Constructed Caves - made by tunnelling into the earth. Although popular around the world, this can be an expensive and dangerous procedure.
• Cut and Cover - also called culvert homes, these are made by assembling precast concrete pipes and containers into the required design of the living space, and then burying them in the ground.
• Earth Berm - house is first built on flat land or a small hill, and then buried, leaving a wall or roof open for light.
• Elevational - house is built into the side of a hill with the front of the home left open.
• Atrium - also called courtyard homes, the rooms are built below the ground around a sunken garden or courtyard that lets light in.
• PSP - stands for post, shoring and polyethylene. House is built by excavating the ground, sinking in posts, placing shoring (boards) between the posts and the earth, and placing polyethylene plastic sheets (for waterproofing) behind the shoring.
• Shaft - an ambitious project in Japan called Alice City plans the construction of a wide and deep cylindrical shaft sunk into the earth with a domed skylight covering, and different levels for business and domestic use built around the shaft.

All underground homes need well-designed ventilation systems to control indoor air quality and humidity. Natural daylight design using light atriums, shafts and wells can also be used to improve the quality of underground living.

Advantages of Building Underground

Underground houses have many advantages over conventional housing. Unlike conventional homes, they can be built on steep surfaces and can maximise space in small areas by going below the ground. In addition the materials excavated in construction can be used in the building process.

Underground houses have less surface area so fewer building materials are used, and maintenance costs are lower. They are also wind, fire and earthquake resistant, providing a secure and safe environment in extreme weather.

One of the greatest benefits of underground living is energy efficiency. The earth's subsurface temperature remains stable, so underground dwellings benefit from geothermal mass and heat exchange, staying cool in the summer and warm in the winter. This saves around 80% in energy costs. By incorporating solar design this energy bill can be reduced to zero, providing hot water and heat to the home all year round. An additional benefit of the surrounding earth is noise insulation. Underground homes are exceptionally quiet places to live.

Finally, underground houses blend with the natural landscape, and have minimum impact on the local ecology. This is not only aesthetically pleasing but ensures that the maximum habitat is left alone for wildlife.

Designing Down for a Sustainable Future

Underground construction is not a new industry, but it is often overlooked as a design strategy for sustainable building. A well-designed underground home can be a stylish, comfortable, secure, bright and inspiring place to live. More than that it is an excellent example of the eco-home ideal, demonstrating energy efficiency, low-impact design and harmony with its natural surroundings. With the increasing demand for more development sites and ever-diminishing green spaces, along with the enforcement of stricter regulations for greener homes, building underground seems the obvious way down.