18. Look through some information about underground construction and answer the following questions:

1. Is it possible to build underground wherever you like?

2. In what way is underground construction connected to green building approach?

3. Do you think it is a widespread construction technique? If so, give some examples of it.

4. What are the main advantages of subterranean homes

5. Can you think of any disadvantages of building such houses?

6. Would you like to live in such a house or would you prefer a conventional one?

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.

Factors determining the design of an underground home:

1. soil type

2. topography

3. precipitation

4. ground water levels

5. load-bearing properties

6. slope stability.

7. availability of waterproof, durable construction materials strong enough to withstand underground pressure (concrete is frequently used).

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.

Advantages of building underground

Houses can be built on steep surfaces and can maximize 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.