Energy Efficient Building Designs and Materials  Printable view

Hong Kong is a city of many high-rise, large-scale development projects and extravagant light displays. To maintain all these requires a huge amount of energy. It is estimated that over 30% of Hong Kong's electricity is consumed by air conditioning systems alone [1]. Any measures that can be implemented to save energy are thus very important.

Fig. 1   Mineral wool is used behind the glass curtain walls of the Central Plaza for heat insulation.

Mineral wool is used behind the glass curtain walls of the Central Plaza for heat insulation. The government has helped facilitate the implementation of energy efficient designs and features into our buildings. Various government departments have put forth different codes and regulations for building construction. For example, reducing heat transfer into a building helps to save the energy consumed by air conditioning. The Building (Energy Efficiency) Regulation gives a statutory requirement that the overall thermal transfer value (OTTV) through the surface of a building should not exceed 35 watts per square metre [2]. In addition, the government has launched an Energy Efficiency Registration Scheme for buildings. Registration certificates will be issued to owners or designers who manage or design buildings that satisfy the minimum standards of the scheme.

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Building orientation and environment

Fig. 2   Some buildings have the long axis running east-west. Smaller surface areas facing east and west receive less sunlight in the early morning and late afternoon of summer months, while a larger surface facing south receives more sunlight at noon over the winter months.

To lower the OTTV of a building, building orientation has to be considered. Many buildings in Hong Kong have the long axis running east-west (Fig. 2). Since the sun is at a low angle in early morning and late afternoon, buildings with smaller surface areas facing east and west receive less solar radiation during the summer months. Heating by direct sunlight is thus reduced and the energy required for air conditioning is also reduced. In winter, the sun's path is more southerly. Buildings with a larger surface area facing south receive more sunlight reducing the energy consumption required for heating. Traditionally, Chinese people prefer south facing homes and avoid windows facing west. There is a certain amount of scientific basis for this.

Fig. 3   Vegetation and water provide a pleasing environment for buildings.

Besides the orientation, the amount of vegetation, especially trees, surrounding the building is also important. Trees provide shading and a pleasing environment. The evaporation of water from their leaves helps to cool the surroundings.