Rapid urbanisation, with its resulting addition of asphalt, concrete and glass, increase of heat emission from transportation and air-conditioning units, as well as high-density high-rise buildings, has greatly intensified the urban heat island effect.

The synergistic interaction between low airflow and the humid environment results in the accumulation of pollutants and fine particles, causing serious air pollution in the city. Urban greening, however, can help improve the air quality, regulate temperature and reduce carbon emissions.

The green building industry is growing in recent years because green buildings can reduce the energy used for indoor air-conditioning, alleviate urban heat island directly, extend the life of the building's surface, block sounds, improve air quality, increase biodiversity by helping sustain and provide habitat and nesting places for various species as well as beautify our environment. Taking into account Hong Kong's space constraints, some new greening concepts such as vertical greening, also known as green wall, have been proposed to solve the problems associated with rapid urbanisation. In fact, compared with a green roof, a green wall can cover more wall surface of a building and ameliorate air pollution.

Vertical greening refers to vegetation that grows directly onto a building's facade or vegetation that is grown on a separate structural system that can be freestanding and adjacent or attached to the wall so that the plant does not need to take root on the ground. In addition to introducing different horizontal greening initiatives, the Government is also examining other ways to increase the green area of a building. Since 2001, the Government has been applying vertical greening elements in various building projects including schools, crematoria, hospitals, offices and community centres. After that, the Government introduced more green facilities into existing government buildings and from 2008, vertical greening designs have been incorporated into appropriate new government building projects.

There are many successful greening projects in Hong Kong, for example:

1. Kai Tak Cruise Terminal

This major tourism infrastructure project boasts a landscaped deck of about 23,000 square metres, one of the largest public roof gardens in Hong Kong. A rain water and air-conditioning condensate recycling system has been adopted for irrigation purposes.

2. North Lantau Hospital

The public hospital features extensive application of skyrise greening including roof greening and vertical greening at various levels of the podium as far as practicable. The overall greening provides environmental benefits as well as an enhanced aesthetic quality to the hospital environment.

3. Hong Kong Science Park

The Park incorporates the concept of sustainability into building design by introducing 39 eco-friendly features including solar wall, ice storage air-conditioning system, solar/wind power lighting system, daylighting, and natural ventilation podium so as to save energy and protect the environment, thus achieving sustainability.

4. Hong Kong Baptist University

HKBU has a number of green spaces around campus, including Sculpture Garden at Communication and Visual Arts Building, Herbs Corner at The Wing Lung Bank Building for Business Studies (4/F) and Floral Garden at David C Lam Building (5/F). Green roofs are also situated in Sir Run Run Shaw Building, Student Halls, Communication and Visual Arts Building and Sing Tao Building, enabling everyone to enjoy the benefit of greening and enhance public awareness of environmental protection.