By: Myles Banfield

Green infrastructure refers to systems that provide various ecosystem services. There is a wide variety of strategies for implementing green infrastructure in the urban environment, including urban geometry, environmentally friendly building materials, and plant-based systems. Different strategies are designed to be applied to areas where they can have the greatest impact.

Urban geometry is a development strategy that refers to the location, height, and orientation of buildings in an urban setting⁷. These factors impact airflow through a city. In today’s cities, buildings are not placed in a way that allows for significant airflow, which worsens the heat-island effect, the tendency for cities to have significantly higher temperatures than surrounding areas⁹. The EPA has determined that cities can be up to 20 degrees warmer than surrounding areas⁹. Temperature increases lead to increased energy consumption² as electricity demand for air conditioning increases. Since most companies rely on fossil fuels to meet this demand, the amount of greenhouse gas emissions also increases¹¹. Controlled airflow through cities enables areas to be cooled down and allows for the dispersal of pollutants⁷.

Building materials typically used in todays buildings—such as concrete, wood, and steel—have many adverse environmental impacts that arise from their creation and use². The construction industry is one of the most active industries all over the world, producing about 30 percent of carbon dioxide emissions². According to Yahong Dong, teaching fellow at The Technological and Higher Education Institute of Hong Kong, changing the materials that we use to build our buildings can have a significant impact on climate resiliency and can also extend the life cycle of buildings, making them more cost efficient as they will require less maintenance and use less energy⁴. The University of Seoul Agricultural Department has conducted research on smart materials. These are described as natural, metal, ceramic, polymer, and composite substances that can be implemented in various buildings that reduce energy consumption and pollution⁸.

Cool roofs are designed to reduce the temperature of buildings by placing a surface that reflects sunlight instead of absorbing it⁶. As a result, energy performance is improved and less electricity is consumed⁶. In fact, cool roofs have been shown to reduce energy consumption by up to 30 percent during the summer³.  If a building is cooler, less air conditioning, fans, and other cooling appliances will be used to keep a comfortable temperature. Reducing the use of electricity also reduces the need for electric companies to burn fossil fuels⁶.

When cities are created, buildings roads, and other infrastructure that is impermeable and unable to retain moisture replace open land and vegetation⁹. Plant-based green infrastructure strategies are designed to remedy this impermeability and improve air quality. A study done in the UK showed that strategic urban planting of trees and hedges reduced the amount of particulate matter in the air by up to 30%¹.  Plant-based green infrastructure strategies also aid in the removal of pollutants from stormwater, which can contain chemical waste, waste from livestock operations, and acid rain. This polluted water contaminates the natural environment, decreases crop yields, and can taint our drinking water. Retention basins are vegetated basins with controlled outlets that slow runoff. Rain gardens may be placed at the bottom of eavestroughs to capture water that runs along rooftops. Additionally, porous pavement may be used in coordination with plant-based strategies to further address impermeability.⁵ All of these green infrastructure strategies exist to absorb and/or slow the release of stormwater runoff as well as the pollutants that it contains.

Green infrastructure is a versatile and effective strategy that provides many ways to reduce a city’s environmental impact. Climate change has become one of the most important problems that the global community is facing and has partially been caused by inefficient development practices. The UN has stated that the global population is projected to reach 9.8 billion by 2050¹⁰. Green infrastructure strategies provide environmentally-regenerative strategies to tackle the issues of rising populations and climate change.

References

1. Abhijith, K.v., and Prashant Kumar. “Field Investigations for Evaluating Green Infrastructure Effects on Air Quality in Open-Road Conditions.” Atmospheric Environment, vol. 201, 2019, pp. 132–147., doi:10.1016/j.atmosenv.2018.12.036.
2. Achenza, M. “Thermal Insulation for a Sustainable Rehabilitation of Traditional Buildings.” Vernacular and Earthen Architecture: Conservation and Sustainability, 2017, doi:10.1201/9781315267739-48.
3. “Cool Roof Impacts on a School-Building Thermal and Energy Performance in Athens, Greece.” NeuroImage, Academic Press, 11 Apr. 2017, sciencedirect.com/science/article/pii/S187802961730107X?via=ihub.
4. Dong, Yahong. “Life Cycle Sustainability Assessment Modeling of Building Construction.” ACI Structural Journal, doi:10.5353/th_b5270551
5. Environmental Protection Agency. “Green Parking Lot Resource Guide.” EPA, Environmental Protection Agency, nepis.epa.gov/Exe/ZyNET.exe/P100D97A.txt?
6. “Experimental Analysis on the Active and Passive Cool Roof Systems for Industrial Buildings in Malaysia.” NeuroImage, Academic Press, 2 May 2018, sciencedirect.com/science/article/pii/S2352710217307933?via=ihub.
7. “Impact of Urban Geometry on Outdoor Thermal Comfort and Air Quality from Field Measurements in Curitiba, Brazil.” NeuroImage, Academic Press, 22 Sept. 2010, sciencedirect.com/science/article/pii/S0360132310002763.
8. Jones, D. G., et al. “Sustainability Assessment Considering Asset and Building Life Cycles.” Smart & Sustainable Built Environments, 2008, pp. 321–334., doi:10.1002/9780470759493.ch29.
9. “Learn About Heat Islands.” EPA, Environmental Protection Agency, 11 Jan. 2017, epa.gov/heat-islands/learn-about-heat-islands
10. “World Population Projected to Reach 9.7 Billion by 2050 | UN DESA Department of Economic and Social Affairs.” United Nations, United Nations, un.org/en/development/desa/news/population/2015-report.html.
11. Yang, Jinxing, et al. “Effects of Urban Geometry on Turbulent Fluxes: A Remote Sensing Perspective.” An Introduction to Biometric Recognition – IEEE Journals & Magazine, Wiley-IEEE Press, 12 Dec. 2016, ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7589050.