Development of modular green roofs for high-density urban cities

Abstract

Many cities are facing problems of urban heat island and lack of greenery space. Green roofs can help mitigate the adverse effects and bring the nature back to the urban area. To apply them effectively, it is important to evaluate the constraints and identify critical factors for planning and designing the green roofs. Modular green roofs have a good potential to suit high-density urban conditions because they can offer better flexibility, convenience and cost optimisation. This paper presents the research findings to develop modular green roof systems for high-density urban cities. Three different types of modular green roofs, including mat, tray and sack systems, were studied by assessing their designs and characteristics. The urban environment and typical buildings for green roof applications in Hong Kong were evaluated. Useful information was obtained to help design and select modular green roofs that can fit into high-density urban environment. In Hong Kong, the high-rise buildings have very limited roof spaces. It is usually more effective to apply green roofs to the top of medium- or low-rise buildings/structures or the intermediate podium roofs. For existing buildings, as they often have constraints on roof structural loading, it is necessary to select extremely lightweight systems. Modular green roofs can be designed to achieve this by adopting suitable vegetation and components. They can also provide greater flexibility for instant greening, future modification and maintenance. By optimising the manufacturing, nursery and installation processes, it is possible to reduce the unit cost of green roofs and allow wider spread.