Sustainable Gardens in Urban Spaces

Research Question

How can we make green roofs and vertical gardens more sustainable and widely adopted into existing buildings?

Importance of Research

In our quest for sustainable and eco-friendly city living, rooftop and vertical gardens could be potential game changers. These green spaces, often overlooked, have the potential to make our cities more sustainable and combat many environmental issues such as Urban Island Effect (UIF), stormwater management, and boost biodiversity. Additionally, they can offer recreational benefits, the aesthetics of nature, and the cultivation of fresh, locally sourced food.

Benefits of Green Roof and Vertical Gardens

Urban Island Effect

The Urban Heat Island (UHI) effect refers to the phenomenon where urban areas experience significantly higher temperatures than their surrounding rural areas (Feitosa et al., 2018). This heat disparity is primarily caused by human activities such as the construction of buildings, roads, and other infrastructure, which absorb and retain heat, as well as the reduction of vegetation and green spaces, which would otherwise provide cooling through shade and evapotranspiration. The UHI effect can exacerbate heat-related health issues, increase energy consumption for cooling, and contribute to environmental degradation. Green roofs and vertical gardens offer a sustainable solution to mitigate the UHI effect by providing natural cooling through evapotranspiration, shading, and insulation, thereby enhancing urban comfort and reducing energy demands for air conditioning.

City Hall, Chicago (Before)

Built in 1911, Chicago City Hall housed government offices and chambers for officials. Designed by architects Holabird & Roche, it had a neoclassical style with a notable domed roof and grand façade. Before the green roof, the roof was covered in standard materials like asphalt or tar.

City Hall, Chicago (After)

City Hall's green roof not only keeps it cooler than neighboring buildings in downtown Chicago during hot summers but also saves the city almost $10,000 annually in energy costs. This is due to the greenery reflecting sunlight, making City Hall more comfortable and reducing overall urban heat.

For more information regarding the City Hall in Chicago, visit the project profile document: https://usa.sika.com/dam/dms/us01/8/chicago-city-hall.pdf

Storm Water Management

Stormwater management is a critical issue in urban areas, where impervious surfaces such as roads, parking lots, and buildings prevent rainwater from infiltrating the soil, leading to increased runoff and flooding risks. Green roofs and vertical gardens play a crucial role in mitigating these challenges by absorbing and storing rainwater, reducing runoff, and alleviating pressure on drainage systems (Barnhart et al., 2021). Through the use of vegetation and permeable substrates, green roofs can effectively capture rainwater and release it slowly, mimicking natural hydrological processes. This not only helps to manage stormwater but also improves water quality by filtering pollutants and reducing the risk of combined sewer overflows. Additionally, vertical gardens can contribute to stormwater management by intercepting rainfall and promoting infiltration, further enhancing the resilience of urban areas to flooding and water-related hazards.

Drainage

Green spaces facilitate the even dispersion of water through layered planted systems, enabling efficient water absorption. This helps prevent water from immediately running off impervious surfaces such as non-planted roofs, concrete, and asphalt.

Toxins and Waste

Preventing urban flooding mitigates the entry of plastic waste into bodies of water. Additionally, green spaces facilitate natural water filtration through phytoremediation.

Phytoremediation: a process in which plants absorb toxins and pollutants through their roots.

Biodiversity

Green roofs and vertical gardens contribute significantly to urban biodiversity by providing habitats for native plant species and supporting diverse ecosystems within city environments (Ksiazek-Mikenas et al., 2021). These green spaces offer opportunities for plant colonization, insect pollination, and bird nesting, thereby enhancing local biodiversity and promoting ecological resilience in urban areas. By incorporating native vegetation and habitat analog approaches, green roofs can attract a wide range of wildlife, including insects, birds, and small mammals, creating interconnected green corridors within the urban landscape (Wang, 2022). This not only helps to conserve biodiversity but also enhances ecosystem services such as pollination, pest control, and seed dispersal, contributing to the overall health and sustainability of urban ecosystems. Additionally, green roofs and vertical gardens can serve as educational tools for raising awareness about the importance of biodiversity conservation and fostering a sense of stewardship among urban residents.

Migratory Birds

Green spaces and green roofs play a vital role in supporting migratory birds such as the American Robin within urban environments. These areas not only offer nesting sites and food sources but also help replace the natural habitats lost due to urbanization. By incorporating native plant species and habitat analog approaches, green roofs provide familiar environments for birds, resembling the ecosystems they would encounter in their natural habitats. This encourages birds to utilize these spaces for resting, foraging, and nesting during their migrations, contributing to the preservation of biodiversity and the well-being of migratory bird populations in cities.

Image: The American Robin

Insects

Green spaces and green roofs are crucial for supporting the habitat needs of insects like the common eastern bumblebee within urban areas. These areas offer essential foraging and nesting sites for native insects- replacing thier natural habitats lost due to urbanization. Installing artificial bee hives on green roofs provides additional nesting opportunities for bumblebees. These hives can also collect honey, supporting local ecosystems and promoting pollinator conservation efforts. These initiatives contribute to biodiversity and help reestablish natice species their ecological niche, which may have been degraded by the introduction of other invasive species.

Image: Eastern Common Bumblebee

Recreational and Asthetics

Green roofs offer urban residents natural spaces that mimic what once existed in the area before urbanization. These elevated green areas provide a glimpse into the natural landscapes that once graced the cityscape, offering a refreshing contrast to the concrete jungle. By recreating elements of the pre-urban environment, such as native vegetation and greenery, green roofs serve as reminders of the natural beauty that once flourished in the area. Residents can experience a sense of connection to the land's history and heritage as they enjoy the tranquil ambiance and biodiversity of these rooftop havens. Additionally, green roofs contribute to urban biodiversity by providing habitats for native plants and wildlife, further enriching the ecological diversity of the area. Overall, green roofs not only offer recreational opportunities but also serve as living reminders of the natural landscapes that once thrived in urban areas, fostering a deeper appreciation for the environment and its preservation.

San Francisco Station

The Salesforce park, located atop of San Francisco Station, is a serene escape in the heart of the city. With its lush gardens, winding pathways, and panoramic views of the urban landscape, it attracts thousands of visitors each year, providing a tranquil retreat amidst the bustling cityscape.

Image from roof

The picture shows the view from Salesforce Park's rooftop in San Francisco, with the city skyline in the background. The greenery of the park's gardens stands out against the cityscape, adding natural beauty to the urban scene.

Local Food Sources

Growing locally sourced fruits and vegetables on green roofs offers numerous benefits. Firstly, it promotes sustainability by reducing the carbon footprint associated with transporting produce from distant locations. By cultivating food directly in urban areas, green roofs minimize the need for long-distance transportation, thus lowering greenhouse gas emissions and reliance on fossil fuels. Additionally, locally grown fruits and vegetables are fresher and more nutritious since they can be harvested at peak ripeness and consumed soon after, retaining their flavor and nutritional value. Moreover, green roofs contribute to food security by providing access to fresh produce within densely populated urban areas, particularly in neighborhoods lacking access to grocery stores or farmers' markets. By integrating agriculture into urban spaces, green roofs not only enhance the aesthetic appeal of buildings but also promote healthier and more sustainable food systems for cities.

Restaurant Gardens

Riverpark restaurant in New York city utilizes unused roof space to grow its own produce. This innovative approach allows the chefs to grow various vegetables and herbs, including 11 types of basil, six varieties of tomatoes, and the unique ice plant.

Community Gardens

The rooftop community garden at 550 Vanderbilt Avenue in Prospect Heights, Brooklyn, lets residents enjoy farm-fresh produce right where they live. Growing fruits and vegetables on-site means residents have easy access to healthy, locally sourced food. They can pick ingredients straight from the garden, making their meals tastier and more nutritious.

Theroretical Framework

This proposal applies the Triple Bottom Line framework to the implementation of green roofs and vertical gardens. These systems aim to achieve a balance between social, environmental, and economic factors, aligning with the goals of urban agriculture. By introducing green roofs and vertical gardens, we can address social issues like food insecurity, environmental concerns related to industrial agriculture's impact, and economic challenges such as limited access to nutritious food. These goals align with the Triple Bottom Line's aim to enhance sustainability across social, environmental, and economic domains, ultimately improving the well-being of individuals and the planet.

Methods

To comprehensively investigate the sustainability and widespread adoption of green roofs and vertical gardens in existing buildings, a potential multiple-methods study could be employed. This approach integrates various research methods, including qualitative and quantitative techniques, to provide a comprehensive analysis of the topic. Qualitative methods, such as semi-structured interviews and discussions, delved into stakeholders' perspectives, attitudes, and experiences regarding green roof implementation (Feitosa et al., 2018; Ksiazek-Mikenas et al., 2021). These insights offered valuable qualitative data on the social and practical aspects of green roof adoption. Additionally, quantitative methods, such as surveys and data analysis, were utilized to quantify adoption rates, preferences, and perceived benefits (Barnhart et al., 2021; Shaniqua et al., 2018). Environmental impact assessments and financial analyses also contributed quantitative data on the benefits and challenges of green roofs and vertical gardens (Viecco et al., 2021; Wang, 2022). By employing multiple research methods, this study aimed to capture a holistic understanding of the factors influencing the adoption and sustainability of green roofs and vertical gardens in urban environments.

In addition to the multiple-methods approach, conducting comparative case studies offered further insights into the sustainability and adoption of green roofs and vertical gardens. These case studies involved analyzing buildings that had successfully implemented green roofs alongside those that had not (Radwan, 2017; Ragab & Abdelrady, 2020). By comparing factors such as building characteristics, environmental conditions, financial investments, and community engagement, researchers could identify key determinants of successful implementation. Furthermore, longitudinal studies tracking the performance of green roof installations over time provided valuable data on their long-term benefits and challenges (He & Jim, 2010; Karachaliou et al., 2016). Incorporating comparative case studies into the multiple-methods approach enhanced the study's depth and breadth, offering a nuanced understanding of the contextual factors shaping the adoption and sustainability of green roofs and vertical gardens.

Importance of Interviewing Stakeholders

Provides insights into stakeholders' perspectives and attitudes
Helps understand stakeholders' experiences related to green roof implementation
Allows for the identification of potential barriers and challenges from stakeholders' viewpoints
Facilitates gathering qualitative data on the social aspects of green roof adoption
Enables stakeholders to express their preferences and concerns directly

Importance of Comparing Case Studies

Offers insights into factors contributing to successful green roof implementation
Identifies key determinants influencing adoption and sustainability
Allows for comparison between successful and unsuccessful implementation scenarios
Helps understand the contextual factors shaping green roof adoption
Provides a nuanced understanding of the challenges and benefits associated with green roofs in different contexts

References

Barnhart, B., Pettus, P., Halama, J., McKane, R., Mayer, P., Djang, K., Brookes, A., & Moskal, L. M. (2021). Modeling the hydrologic effects of watershed-scale green roof implementation in the Pacific Northwest, United States. Journal of Environmental Management, 277, 111418. https://doi.org/10.1016/j.jenvman.2020.111418

Castiglia Feitosa, R., & Wilkinson, S. J. (2018). Attenuating heat stress through green roof and green wall retrofit. Building and Environment, 140, 11–22. https://doi.org/10.1016/j.buildenv.2018.05.034

Goda, Z. M. A., Foda, M. A. M., & Elsayyad, N. A. E. (2023). Using Green Roofs for Social Housing to Improve Energy Consumption in New Cities. (An Applied Study of Social Housing in Egypt’s New Cairo City). Future Cities and Environment, 9(1), 2. https://doi.org/10.5334/fce.165

He, H., & Jim, C. Y. (2010). Simulation of thermodynamic transmission in green roof ecosystem. Ecological Modelling,221(24), 2949–2958. https://doi.org/10.1016/j.ecolmodel.2010.09.002

Jiang, N., Zou, W., Lu, Y., Liao, Z., & Wu, L. (2024). Using Recycled Construction Waste Materials with Varying Components and Particle Sizes for Extensive Green Roof Substrates: Assessment of Its Effects on Vegetation Development. Sustainability, 16(1), 414. https://doi.org/10.3390/su16010414

Karachaliou, P., Santamouris, M., & Pangalou, H. (2016). Experimental and numerical analysis of the energy performance of a large scale intensive green roof system installed on an office building in Athens. Energy and Buildings, 114, 256–264. https://doi.org/10.1016/j.enbuild.2015.04.055

Ksiazek‐Mikenas, K., Chaudhary, V. B., Larkin, D. J., & Skogen, K. A. (2021). A habitat analog approach establishes native plant communities on green roofs. Ecosphere, 12(9), e03754. https://doi.org/10.1002/ecs2.3754

Radwan, A. H. (2017). Green Roofs - A Sustainable Tool of Healthier Cities, Applications in Egypt. SSRN Electronic Journal. https://doi.org/10.2139/ssrn.3163416

Ragab, A., & Abdelrady, A. (2020). Impact of Green Roofs on Energy Demand for Cooling in Egyptian Buildings. Sustainability, 12(14), 5729. https://doi.org/10.3390/su12145729

Shafique, M., Kim, R., & Rafiq, M. (2018). Green roof benefits, opportunities and challenges – A review. Renewable and Sustainable Energy Reviews, 90, 757–773. https://doi.org/10.1016/j.rser.2018.04.006

Viecco, M., Jorquera, H., Sharma, A., Bustamante, W., Fernando, H. J. S., & Vera, S. (2021). Green roofs and green walls layouts for improved urban air quality by mitigating particulate matter. Building and Environment, 204, 108120. https://doi.org/10.1016/j.buildenv.2021.108120

Wang, L., Wang, H., Wang, Y., Che, Y., Ge, Z., & Mao, L. (2022). The relationship between green roofs and urban biodiversity: a systematic review. Biodiversity and Conservation, 31(7), 1771–1796. https://doi.org/10.1007/s10531-022-02436-3

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