Session 14 // Emerging Green Roof Research

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No Prerequisite Required
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1) Current and Potential Uses of Hospital Greenroofs
Plants and planted landscapes are recognized for their therapeutic benefits. Hospitals are increasingly adopting therapeutic landscapes like healing gardens, horticultural therapy gardens, and memory gardens. Research on the therapeutic benefits of greenroofs in hospital settings is limited. The primary objective of this project is to understand the current and potential uses of hospital greenroofs and associated motivations for their installation. We have documented 97 hospitals nationwide which have greenroofs. Of the 97 hospitals, 73 were general care. We found that 56 hospitals had accessible greenroofs. Phone interviews were conducted with key stakeholders who played a major role in the planning and maintenance of these hospital greenroofs. The questions focused on greenroof installation motive, accessibility, and therapeutic benefits. Thirteen interviews have been coded and analyzed using Dedoose software. Preliminary themes emerging from the interviews suggest that stormwater management, building energy, and therapeutic benefits were primary motivations for installation. Ongoing site use mapping and staff surveys will build on these interview findings. This information will be useful for determining how future greenroofs can be designed for hospital settings to promote horticultural therapy.

2) Biochar improves runoff water quality from green roof plots
Green roofs have the potential to act as pollutant sources, mostly due to the nutrients nitrogen (N) and phosphorus (P) leaching from the substrate. Designing substrate to reduce this effect, while continuing to provide nutrients for plants, is essential to minimize this ecosystem disservice. Over two growing seasons, our study evaluated plant cover, nutrient retention and water retention in extensive green roof plots after the addition of biochar to the substrate. Biochar is a water-retaining soil additive with the potential to aid in storm water retention and to bind nutrients, making them plant available whilst improving water runoff quality. Replicated plots of biochar-amended substrate treatments were established, both vegetated (Sedum mixture) and unvegetated. Although neither plant cover nor water retention significantly improved, biochar addition improved water quality by decreasing phosphorus, organic carbon and organic nitrogen export, all of which were high in runoff from the standard green roof substrate. Biochar was found to be a source of nitrate, but this was counteracted by plant presence, with plants sequestering N. Biochar-amended substrate appeared to bind P, while N retention occurred due to a biochar-plant interaction. These results suggest that biochar could be a useful amendment for the green roof industry.

3) Trials and tribulations of plant diversity - new plants appropriate for green roof use and benefits of mixed communities
In 2016, 55 species were seeded on green roofs set up in central Pennsylvania at the Russell E. Larson Agricultural Research Center at Rock Springs, irrigated for establishment, and monitored through 2017 (with 2018 recording included by conference time). 42 of these species survived and prospered within their square foot plots (5 replications of each). With no additional irrigation, the level of success could not have been predicted. When tested for water use, two trials with 5 species each - the first trial used wild type seed for transplants grown in house and the second trial used cultivars of native analogs grown by professional green houses. The evapotranspiration
New York City, NY
Distance Learning
Course Equivalency
Energy Conservation / Renewable Energy
Health, Safety and Welfare
Learning Outcomes
1) • Recognize how building type and use can have different implications for design and use
• Understand the unique strengths and challenges presented by greenroofs on hospitals
• Consider different design features that promote horticultural therapy on hospital greenroofs

2) • Understand the importance of manipulating greenroof substrate to reduce negative environmental impacts and why biochar is a possible solution
• Understand the possible mechanisms by which biochar can improve greenroof substrate nutrient retention, water retention, and plant performance
• Be able to analyze the overall effect of biochar amended greenroofs on the provision of key ecosystem services

3) • Expanding species use on green roofs
• Understanding water dynamics in complex extensive systems
• Shifting focus on engineering green roofs towards building landscapes
1) Arjun Viray - Portland State University2) Alicia Goldschmidt - University of Cincinnati Biological Services3) Julie Razryadov - Pennsylvania State University
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Course Codes
Green Roofs for Healthy Cities

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