Applications of extensive green-roof systems in contributing to sustainable development in densely populated cities: A Hong Kong study

Developed cities such as Hong Kong are usually densely populated. Since the land is limited, high-rise buildings are constructed. When buildings become higher, air flow is reduced and heat is trapped among high-rise buildings. The air temperature will be greatly increased and air pollution becomes a serious problem. To reduce air temperature caused by the wall-effects, various methods have been developed. One typical method is the use of green roof systems. The application of extensive green roofs on existing buildings has been recommended in Hong Kong since 2001. The advantage of this practice is that no additional floor area is required and it can also improve urban greenery. Although a green roof system has been introduced and adopted in Hong Kong since 2001, the emphasis is mainly given to the application of intensive green roofs for podium gardens instead of extensive green roofs. This paper investigates the current practice of using extensive green roofs in Hong Kong. The constraints in applying extensive green roofs are investigated, which leads to studying the solutions for mitigating these constraints and improving the future development of the implementation.