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How Green Roofs Can Combat Climate Change

By: Ava H.

In a time where the urgency of climate change continues to worry citizens, it can be difficult to find effective solutions that are convenient to implement within society. However, there is a simple solution that imposes many environmental benefits, and would only involve the roof over your head: green roofs, where a building’s rooftop is covered with vegetation. Studying environmental problems is interdisciplinary, meaning that there are many fields that come into play when analyzing climate change. Therefore, institutional reform can be a convenient method to encourage urban spaces to adopt sustainable practices that are attainable. After all, institutions on all levels, from government buildings to community colleges can easily adopt green roofs to reflect the interrelation of environmental and economic problems.

Implementing green roofs on buildings that already exist is an amazing architectural method to utilize valuable space in cities, and can create new opportunities for sustainable businesses. For example, my family purchases basil from Gotham Greens, an environmentally-driven farming company which locally grows its food from rooftop greenhouses in Chicago, where I live. Due to Gotham Greens’ imaginative outlook on putting vacant urban spaces to good use, the futuristic farm is able to produce high-quality greens by using significantly less water, land, and energy.

Gotham Greens’ rooftop greenhouse in Pullman. Photo from: Chicago Sun-Times

While it is outstanding that a small business has the means to accomplish such sustainable achievements, insightful policy makers within cities are needed in order to expand the productive idea of green roofs. Although this environmental practice may not be well known within the US yet, green roofs have been sufficiently tested and established within Europe for over 30 years. In fact, cities such as Copenhagen and Stuttgart mandate green roofs for most of their new construction projects.

Copenhagen’s green ski slope on top of a waste-to-energy plant.

Photo from: Smart City Lab

Believe it or not, the opportunities for green roofs are much more available than perceived. The chart below highlights that many American cities such as these four can have over 20 percent of their land covered by roofs. With this much vacant space on top of buildings, the expansion of green roofs can create a widespread impact on cities. As the demand for green roofs is only increasing, American ecologists must study how green roofs prove to be a successful endeavor in Europe to increasingly integrate these plant practices in the United States.

Photo from: Environmental Protection Agency (EPA)

The benefits of green roofs prove to be endless. In cities known to flood often, green roofs pose a viable solution, as they would absorb much of the excess rainwater. Due to their layer of plant material, green roofs are able to take in water like a sponge. Plants are able to capture the excess rainwater and slowly release it through their leaves, through a process known as evapotranspiration.

A conceptual diagram of how evapotranspiration works on a green roof.

Photo from: ResearchGate

Without rainwater absorption, urban environments face an increased risk of flooding, as sewer systems would continue to be over-stressed. Due to increased storms from climate change, green roofs are more needed than ever, as they would aid cities with stormwater management capacity.

The graph demonstrates how runoff is substantially reduced for green roofs as opposed to bare roofs. Photo from: Environmental Studies Lecture

In addition, green roofs reduce greenhouse gas emissions, since the plants take in carbon dioxide. Because green roofs reduce buildings’ energy use, air pollution from energy production is lowered as well. Through dry deposition, plant surfaces are able to remove pollutants from the air, such as particulate matter, carbon monoxide, sulfur dioxide, ground-level ozone, and more. Studies have confirmed this benefit of green roofs, including one for Washington DC that estimates 6 tons of ground-level ozone would be removed annually if green roofs cover about 20 million square feet. Global warming continues to threaten civilians’ everyday life, through life-threatening heat waves and increased mental health problems as mentioned in Air Pollution on the Mind. However, since cities emit 60% of global greenhouse gas emissions, incorporating green roofs’ emission reducing properties would have an immense effect in mitigating global warming effects. With all of these environmental benefits and more, green roofs prove to help slow disastrous environmental effects of cities while increasing the wellbeing of citizens.

Photo from: Science Direct

Although some American developers continue to be hesitant to green roofs because of their initial high price, green roofs are becoming increasingly popular within many US cities. Chicago continues to be a leader within the US green roofs movement, with over 200 green roofs, covering 2.5 million square feet. Vegetation is featured on a wide range of Chicago building rooftops, from City Hall to a Target store. And with Chicago’s Green Roof Grant Program awarding twenty small projects $5000 each, green roofs are able to further expand to smaller building sites, from single-family homes to a fire house.

Chicago’s city hall features an impressive green roof. Photo from: Inhabitat

Reconstructing cities in order to be more sustainable would be a costly endeavor that many policymakers would unfortunately veto. However, by combining the architecture and scientific data of the benefits of green roofs, cities can easily become more sustainable with few alterations. Depleted natural resources can become replenished with the addition of green roofs throughout a city. Similar to environmental studies, green roofs are quite interdisciplinary and require the understanding of multiple fields in order to be successful. Economists are vital for evaluating the cost efficiency of energy saving components in order to confirm to others that green roofs indeed have economic benefits. Sociologists evaluate how green roofs affect different groups of people and the qualities that individuals value most within these sustainable designs. Science helps provoke sustainable technology to become a reality, and with the insight of several different careers is when the transformative environmental solution of green roofs can be accomplished.

Discussion Questions:

  • Are there any green roofs in your local community? If yes, how have they affected your community? If no, what are some places you think could easily implement green roofs?

  • Would you be willing to integrate a green roof within your home? Why or why not? (Green roofs are still possible on triangular roofs)

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