Quantifying the Fundamental Behavior of Green Roofs in an Urban Environment

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).One emerging alternative to improving the state of inadequate, or decaying, infrastructure in urban environments, which does not involve a perpetuation of large scale, costly systems, is an approach known as low impact development (LID). LID interventions are small-scale interventions that be used at the building, lot or even neighborhood scale to conserve or reuse water, mange storm-water, and/or reduce energy demands. Because LID interventions are a distributed, rather than centralized, form of infrastructure, they also have the potential to build resilience into existing infrastructure systems. Furthermore, as less costly and more ?nimble? infrastructures, LID interventions hold promise as urban adaptation strategies in the face of uncertain of climate change impacts A current LID intervention that is increasingly being adopted in urban environments to manage storm-water impacts, improve environmental conditions and reduce energy consumption, is green roof technology. A green roof is an environmental system that incorporates layers of specialized waterproofing and root-resistant materials, drainage or water storage layers, and a growing medium to support vegetation on a structure?s roof. Although green roofs have been in use for over thirty years in Germany, they are relatively new to North America. Nonetheless, green roofs are rapidly gaining popular attention in the U.S. and have recently become a high-profile component of sustainable building construction: They are lauded for provision of multiple benefits in the urban environment, including stormwater management, building energy savings, mitigation of the urban heat island effect and urban air pollution, and provision of habitat and aesthetic amenity. Numerous groups in the U.S. have initiated research programs to investigate green roof behaviors. These groups are using instrumented model roofs, green roof platforms and larger-scale green roofs on buildings in rural and peri-urban environments to further understanding of green roof performance under a variety of different conditions. The unique contribution of this project to this body of ongoing effort is the quantification of extensive green roof behavior in a dense urban environment, where the complexities of local eco- and climatic conditions, coupled with building density, are likely to significantly impact green roof performance. Over the course of three years, the project will develop a monitored Urban Green Roof Network to quantify: (i) the impact of different plant species and growing medium thickness on green roof behavior, (ii) the contribution of evapotranspiration to stormwater retention and reduction of urban heat island effects, (iii) the quality of green roof water run-off, and (iv) the ability of green roofs to trap air-borne particulates and take up other contaminants such as CO2.Results from the project will be used to improve scientific understanding of green roof performance in an urban environment and help identify green roof configurations that can maximize desired environmental performance objectives. The project will also determine whether data collected from small, instrumented ?green roof test boxes? located on urban roof-tops are useful indicators of urban green roof behavior, and examine the applicability of available groundwater/ geo-environmental modeling software for predicting green roof water balance. The project will enhance infrastructure for research and education by establishing an Urban Green Roof Network in New York City that can be used as a living laboratory for research and educational activities alike. In order to widely distribute project results to a broad audience, a green roof consortium, termed The Columbia University Green Roof Consortium, will be formed to provide a unique forum for urban stakeholders to interact and expand their knowledge of urban green roof behavior. Student research participation and educational/ teaching activities will also be used to expose students at all levels to extensive green roof technology and its potential role in urban sustainable development.