Rooftop “greening” as an option for microclimatic amelioration in a high-density building complex

The University of New South Wales (UNSW) is a major teaching and research institution located in an inner suburb of Sydney, Australia. Growth and intensification of the University’s activities within a spatially constrained site have placed pressure on existing open space within the campus, and limit the development of new vegetated areas on the ground plane. The urban geometry of the site and proliferation of hard surfaces have a marked effect on the local microclimate, outdoor thermal comfort (particularly during Sydney’s hot humid summers) and the energy performance of University buildings.

At the same time, UNSW has developed a strong sustainability profile in its teaching, research and campus operations, including the promotion of synergies between environmental learning and the learning environment as represented by the campus itself. For example, there is growing interest within the UNSW Faculty of the Built Environment in the topic of roof gardens, with the University’s own predominantly flat rooftops seen as potential case studies for teaching and learning.

This research utilises a high-resolution (0.5-10 metre) computer model to simulate the microclimatic effects of a proposed major redevelopment affecting a 30,000 square metre section of campus, with and without the introduction of vegetation (where structurally feasible) on the rooftops of planned and existing buildings and infrastructure.

The site includes the University’s main pedestrian “plaza”, several current and proposed multi-storey buildings, outdoor eating and grassed passive recreation areas, and paved car parking space. The simulation models the climatic conditions of a typical Sydney summer day.

The findings are evaluated in relation to both outdoor thermal comfort and building performance. Additional environmental aspects of roof greening are discussed, and the implications considered from the perspective of connecting teaching and research with the physical fabric and operation of the campus, to address both academic and corporate environmental management goals.