Plant-covered roofing systems

This article first appeared on Undark.

Luis Cassiano was dripping sweat down his cheeks. Rio de Janeiro had its busiest day ever in 2012: The beach city had actually barely exceeded its previous record set in 1984, reaching around 110 degrees Fahrenheit.

Since moving to the Parque Arará slum in northern Rio some 20 years earlier, Cassiano and his mother, then 82, had literally lived in the exact same constrained four-story home. Its rooftop is built of asbestos tiles, like many other homes in the working-class neighbourhood, one of more than 1,000 favelas in the Brazilian city of over 6.77 million people. Nowadays, corrugated steel sheets are often used to cover the roofs of homes in his neighbourhood because of their inexpensive cost. Additionally, it can conduct very hot temperatures.

While the outside temperature was hot enough to successfully fry an egg on his roofing, according to Cassiano, the inside temperature was far worse. I just got home to sleep,” Cassiano said. “I had to get out.”

Parque Arará is similar to many other impoverished urban neighbourhoods, which frequently lack vegetation and are more likely to experience extreme heat than their more affluent or rural counterparts. These areas are sometimes referred to as “heat islands” because they offer pockets of heat that are frequently up to 20 degrees hotter than the surroundings.

Human health suffers as a result of that weather. Heat waves can worsen chronic health disorders, such as respiratory problems, and they can impair brain function. They are also associated with higher incidence of dehydration, heat stroke, and death. As climate change makes heat waves more frequent and severe, such illnesses are likely to become more prevalent. A 2021 study published in Nature Climate Change found that between 1991 and 2018, more than a third of heat-related deaths worldwide may have been caused by global warming.

Cassiano was alarmed by the intense heat. And as a seasoned favela homeowner, he knew he couldn’t rely on Brazil’s federal government to improve living conditions for his Black neighbours who live next door. He opted to do it himself.

Speaking with a friend who works in sustainable development in Germany, Cassiano learned about “green roofings,” an architectural feature in which roofs are covered in vegetation to reduce both indoor and outdoor temperatures. The European nation started taking the idea seriously in the 1960s, and by 2019, it had expanded its green roofs to an estimated 30,000 acres, more than tripling in just a few years.

He had thought, “Why can’t favelas do that too?”

Scientific research suggests that green spaces can offer city dwellers a variety of benefits: In addition to lowering the surrounding temperature, they can reduce stormwater runoff, reduce noise pollution, improve a building’s energy efficiency, and alleviate tension and anxiety.

Since that scorching day in 2012—and a number of subsequent heat records—Cassiano has been the director of Teto Verde Favela, a nonprofit organisation he founded to teach residents how to create their own green roofing systems. Favela construction presents a unique mix of technical challenges and legal difficulties, so Cassiano enlisted the help of local researchers to look into best practises and materials. Even with cost-saving measures, covering the roofs of an entire area requires time and a sizable expenditure.

Although slow, his work has actually been consistent. He still has a long way to go before replacing every roof in his neighbourhood, which has about 20,000 residents. Time might not be on their favour, given how quickly the effects of climate change are appearing. Cassiano still views Teto Verde Favela as a model for people in identical circumstances across the globe.

He said, “I started seeing the entire favela with green roofing systems. “And not just this favela, but also others.”

Although green roofs have been present for a very long time, it wasn’t until the 1960s and 1970s that the modern variety really took off, thanks to improved watering technology and protection against leaks invented in Germany.

The idea uses two techniques to lower local temperatures. Plants absorb less heat than other types of roof materials. Second, evapotranspiration, which is similar to how sweat cools human skin, involves plant roots soaking up water that is then released as vapour through the leaves.

Additionally, green roofs can help prevent flooding by reducing overflow. According to Lucas Camargo da Silva Tassinari, a civil engineer who studies the effectiveness of green roofing systems, a standard roofing system may let 100 percent of rain run off, allowing water to enter streets, but a green roof “can decrease this overflow generation rate to anywhere from 25 to 60 percent,” depending on its structure and slope.

Such actions could be beneficial in Brazil, where rising temperatures and ongoing flooding are problems. According to a 2015 study, the heat islands in the city had actually experienced an increase in land surface temperature of 3 degrees during the preceding years. Plant seems to help: The Federal Rural University of Rio de Janeiro (UFRJ) researchers found a 36 degree difference in land surface area temperature between the city’s warmest neighbourhoods and nearby vegetated areas.

According to Cassiano, the temperature at Parque Arará frequently rises above the official temperature for the city, which is normally measured in less dense areas closer to the ocean. He decided to build the first green roofing model in his neighbourhood on his own home. Cassiano ran upon Bruno Rezende, a civil engineer at UFRJ who was researching green roofings for his doctoral thesis, as he considered the best way to get started. Rezende quickly alerted Parque Arará when he told him about his idea.

When it comes to green roofs, there isn’t necessarily a one-size-fits-all solution. To ensure that a project is not only functional but also structurally sound, a designer must take into account the unique environment and structure of each region.

Problematically, certain green roofing solutions can be quite heavy. They require a number of layers, each of which serves a specific purpose, such as allowing drainage or providing insulation. Like all of Rio’s favelas, Parque Arará was not constructed using computer codes. Without engineers or designers, homes have been built out of necessity using everything from asbestos tiles, sheet metal, and waste wood to bricks, concrete blocks, and bricks. A casual building might not always be able to support the weight of all the layers required for a green roof.

Rezende’s initial suggestion was to cover Cassiano’s roofing with rolls of bidim, a lightweight nonwoven geotextile manufactured from polyester from recycled beverage bottles. This was his response to seeing Cassiano’s covering. They planted a variety of plants inside those rolls of bidim that were left over from a recent building and construction project, including basket plants, inchplants, sneaky inchplants and spiderworts. The rolls were placed in the grooves of the asbestos roofing system, and a watering system that leaked thin down was created as a result.

Rezende brought Cassiano to meet his consultants and offer what they had actually learned, with a low-cost approach to install light-weight green roofing systems. According to Cassiano, the university agreed that the job demonstrated such a commitment to providing products for the future action.

Rezende and André Mantovani, biologists and ecologists from Rio’s Botanical Gardens, returned to Cassiano’s home to see the impact the plants on the roofing had once they had time to mature. For several days, the scientists measured the temperature inside his house to that of a neighbor’s using a number of sensing units placed beneath the roofing systems. (The researchers had intended for their study to go longer, but the favela’s erratic energy system kept disconnecting the power to their sensing units.)

Despite the limitations of the research study, the results were inspiring. Cassiano’s roof was roughly 86 degrees for the duration that scientists tape-recorded temperature measurements. On the other hand, the temperature change of his neighbour next door ranged from 86 to 122 degrees. The two houses’ roofs diverged over forty degrees at one point.

The statistics confirmed Cassiano’s belief that if he wanted to make a difference, he needed to install green roofing on as many homes as possible.

“One home comes to mind when we talk about green roofings. That’s not enough, insisted Marcelo Kozmhinsky, a Recife-based agronomic engineer with a focus on environmentally friendly landscaping. “You know you have something when you start to visualise a street, a block, an area, and a city or neighbourhood as a whole with a number of green roofings. given that the cumulative is the focus. Everyone benefits from it.

Having a larger perspective presents a variety of fresh challenges. A structure must be able to support a green roofing system for it to be secure, and determining a structure’s capacity requires some time. Even with inexpensive materials like bidim, it costs a lot of money to install green roofing on hundreds or thousands of homes.

The cost is the biggest obstacle, according to So Paulo-based architect Bia Rafaelli, who has worked with communities like Cassiano’s to introduce them to sustainable building options. She said, “There would need to be sponsorship from business or assistance from the federal government to make this all practicable on a large scale, installing green roofing systems on all the favelas.

While other Brazilian cities have laws requiring green roofs on new construction wherever possible, Rio de Janeiro does not. Since May 2021, a proposal to create a law that is equivalent to those in other cities has been stalled in the Rio city council.

Nevertheless, Rio encourages home builders to install green roofing systems and other environmentally friendly features, such as solar panels and permeable paving. Locals in the favelas, where the majority of construction is done informally and without the building industry looking to legislation for rules and advantages, typically do not benefit from such initiatives.

Any employment related to the favelas struggles with enduring racism in addition to bureaucracy and other administrative challenges. A 2021 study by Instituto Locomotiva, Data Favela, and Central nica das Favelas found that 67 percent of people living in favelas across Brazil are Black. That is significantly higher than the country’s general population, which is composed of 55% Black people.

Geographer and senior scientist Diosmar Filho, who is in charge of research on inequality and environmental change at the research association Iyaleta, claimed that “public policy does not reach” favelas. He claimed that the working-class areas are heat islands because of ecological bigotry—the disproportionate impact of ecological risks on people of color—which has left much of Brazil’s Black population without access to adequate housing and healthcare, both of which are made worse by the effects of climate change.

These patterns are not exclusive to Brazil. White communities in South African cities had disproportionately higher access to urban green spaces, such as parks and green roofings, according to a 2020 study published in the journal Landscape and Urban Planning. The authors of the study dubbed this “green Apartheid.” Researchers at the University of Michigan used a spatial analysis to determine that green roofs were primarily located in the city’s downtown, which they kept in mind was more White and affluent than the rest of the city. (The research, however, only looked at 10 green roofs and provided very little information.)

According to Filho, Black people typically turn to one another for support in the absence of assistance from the federal government or other authorities. He said, “It’s always the Black population that’s producing lifestyle for the Black population,” citing people like Cassiano and places of employment like Teto Verde Favela.

According to Filho, “Teto Verde’s actions would be a great point of recommendation for metropolitan real estate policy for the decrease of effects of environment modification.” He continued, “That’s when it turns into an ecological bigotry case when towns deny people of colour the right to safe real estate and ways to fight back against climate change.”

Cassiano continues to collaborate with UFRJ researchers and trainees once he returns to Rio. Together, they experiment with new materials and methods to improve the initial green roofing system model installed on his home more than ten years ago. His primary considerations have been to reduce cost and weight to accommodate favela construction.

Cassiano uses a vinyl sheet sandwiched between two layers of bidim as a layer of water-resistant screening rather than an asphalt blanket. This means that the cost of roofing installed by Teto Verde Favela is roughly 5 Brazilian reais, or $1, per square foot. The cost of regular green roofing, however, can go as high as 53 Brazilian reais ($11) for the same amount of area. His roofs also began hydroponically, which means no soil was used, in order to lighten them up.

The 93-year-old mother of Cassiano enjoys caring for the vegetation on their roof. In addition to keeping rainwater from overflowing during a storm and lowering the temperature in their home on hot days, according to Cassiano, it also improves their psychological health.

Cassiano said, “Now I couldn’t live here in this house without this green roofing system.” He added, “When I see birds, when I see butterflies, when I see a flower or a fruit, it makes me very thrilled.

It is much more than I had imagined.

Independent journalist Jill Langlois works out of So Paulo, Brazil. Her work has actually been published in a number of publications, including The New York Times, The Guardian, National Geographic, and TIME.

This article first appeared on Undark. View the introductory article.

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