Urban densification and climate change are creating a multitude of issues for cities around the globe. Contributing factors include increased impervious surfaces that result in poor stormwater management, rising urban temperatures, poor air quality, and a lack of available green space. In the context of volatile weather, there are growing concerns regarding the effects of increased intense rainfalls and how they affect highly populated areas. Green roofs are becoming a stormwater management tool, occupying a growing area of urban roof space in many developed cities. In addition to the water-centric approach to the implementation of green roofs, these systems offer a multitude of benefits across the urban water–energy–food nexus. This paper provides insight to green roof systems available that can be utilized as tools to mitigate the effects of climate change in urbanized areas. A new array of green roof testing modules is presented along with research methods employed to address current issues related to food, energy and water performance optimization. Rainwater runoff after three rain events was observed to be reduced commensurate with the presence of a blue roof retention membrane in the testbed, the growing media depth and type, as well as the productive nature of the plants in the testbed. Preliminary observations indicate that more productive green roof systems may have increasingly positive benefits across the water–energy–food nexus in dense urban areas that are vulnerable to climate disruption.
The installation of a green roof on residential buildings affords the opportunity to sequester carbon from the atmosphere. The cost of incorporating green roofs in the construction of a family home or modifying an existing home is significant and the private benefits are rather small. Carbon reduction does have a value recognized by all levels of government in Canada. In this paper we calculate the cost of installing a green roof on a two vehicle garage in the Province of Ontario using current building costs. Utilizing data on the private costs and private benefits, the estimated NPV of a green roof over a 35 year period is negative. Once the value of carbon sequestering is introduced in the model, the NPV is positive, suggesting that subsidizing green roof construction is an efficient method in any government’s question to encourage a reduction in GHG emission.
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