| |
Hong Kong has an exceptionally compact development mode with a population of seven million largely concentrated in about 200 square kilometres or 20% of the territory’s land. Urban areas are pervasively dominated by tall buildings and roads. Most building lots have high site coverage, often at 100%, leaving meagre ground-level spaces for open spaces or amenity vegetation. Land dedicated to urban greening is very limited in comparison with most cities. The provision of public open spaces, at merely 3 square metres per person, is exceptionally low. Meanwhile, due to excessive urbanization, the city is suffering from the ill impacts of chronic air pollution and progressive intensification of the urban heat island effect. Like many compact cities around the world, it is difficult to increase significantly green spaces in core city areas. Alternative and innovative ideas could be explored to enhance the usable green covers.
“Green roofs are widely considered a means for partial compensation of the loss of natural cover due to construction of buildings…”
Greening in a compact city could extend to the rather neglected vertical dimension, and usher more natural ingredients into built-up areas. The city has numerous high-rise building rooftops devoid of plant cover, and most sites hardly serve any useful purpose. Many cities in Europe, North America and Japan have buildings covered by well designed and vegetated roofs. Some cities have instituted enabling policies and regulations that require new buildings to install green roofs. Some countries, such as Germany and Japan, have enacted statutory requirements that a certain percentage of building roofs have to be covered by living vegetation. Green roofs are widely considered a means for partial compensation of the loss of natural cover due to construction of buildings. It is increasingly enlisted for carbon offset and stormwater management in terms of quantity and quality.
“Making use of the numerous vacant flat rooftops in Hong Kong will add significantly to the green space stock of the city, thus reaping its environmental benefits especially in ameliorating the harsh urban climate...”
Green roofs could bring many environmental benefits which are often neglected or misunderstood. Making use of the numerous vacant flat rooftops in Hong Kong will add significantly to the green space stock of the city, thus reaping its environmental benefits especially in ameliorating the harsh urban climate. The methods of green roof construction and maintenance are not too well grasped by local developers and professionals. An extensive research green roof has been established in 2006 in the University of Hong Kong to study a range of environmental benefits, including evaporative cooling, thermal insulation, heat flux reduction, and energy conservation. It serves as a demonstration site to promote and popularize the green roof idea. The study has aroused much interest in the community, resulting in the adoption of green roof as an official stance in the 2006 policy address.
“Other major Asian cities such as Tokyo, Beijing and Shanghai are actively promoting green roofs. Hong Kong could catch up by adopting a proactive approach to encourage installation...”
The idea of modern green roofs, hitherto largely established in western countries and Japan, is beginning to take root in other Asian and tropical cities. Singapore recently has developed an assiduous program to raise the quality and quantity of green roofs. Other major Asian cities such as Tokyo, Beijing and Shanghai are actively promoting green roofs. Hong Kong could catch up by adopting a proactive approach to encourage installation. New buildings could include green roofs as an integral part of their design, and existing roofs could be retrofitted. The concepts, technology and materials for green roofs are rather mature and advanced in developed nations. They could be modified and localized, especially concerning the choice and husbandry of plants, for application to cities in the Asian subtropical region.
“Green roofs on low-rise buildings are the most effective in terms of environmental benefits and visual-landscape contribution to surrounding high-rise residents...”
The government and some developers are beginning to plan for and establish green roofs mainly on new buildings. Some retrofitting of existing buildings is being contemplated by property companies and home owners. Green roofs on low-rise buildings are the most effective in terms of environmental benefits and visual-landscape contribution to surrounding high-rise residents. Most school buildings in Hong Kong are short, usually no more than eight storeys, and high-rise residential blocks tend to be located nearby. Many schools in Hong Kong lack green spaces and amenity vegetation, and some are deficient in ground-level open spaces. All schools have flat rooftops which are invariably covered by hard surfaces, some of which are used as playgrounds. Herein lies ample opportunities to green their barren roofs, and provide green spaces to improve their environmental quality. Moreover, a simple turf roof could offer a wonderful living carpet for passive recreational activities. Few students and teachers in Hong Kong could enjoy the luxury of sitting and lying on a soft and verdant turf in their schools. Hongkong Bank Foundation has recently provided a grant to the author to donate green roofs to ten local schools under the HSBC Green Roof for Schools Project. On average, each school could be given a roof lawn of about 400 m2. The pioneering project will allow the apparent pipe dream to come true in five schools in 2008, and the remainder to follow soon afterwards.
lie Hoffman, and William McDonough
Synopsis
Citywide networks of green roofs can result in cooler summer temperatures, reduced energy demand, controlled stormwater runoff, protected wildlife habitat, and an enhanced sense of urban well-being. Highlighting these benefits, Green Roofs informs and inspires communities, designers, building owners, and government and business leaders by showcasing the environmental and aesthetic potential of green roofs around the world.
"Imagine the effect of community kitchen gardens on the rooftops of New York City," writes visionary green architect William McDonough in his forward. "The gardens would make visible the vital connections between water, soil, food, and human culture, and create a network of living landscapes across the ancient archipelago that is New York City."
Hundreds of photographs, forty case studies of exemplary green roof projects – from Mexico City to Malmo, Sweden to Fukuoka, Japan to Dearborn, Michigan – provide inspiration and guidance for green roof development, as well as design details. The book includes seven essays on green roof development in Berlin, Tokyo, London, Portland, Chicago, Toronto, and New York City. Additional essays detail the technical requirements, architectural history, and design possibilities of vegetated rooftops.
(Source: Amazon.com)
|
|
|
 |
|
|
