Along the tree-lined sidewalks of Tel Aviv’s Atidim Park, a business and commercial district in the north of the city, a curious new addition to the urban canopy arrived a few months ago.
Looking like something between a satellite dish and a ship’s sail, the structure known as LumiWeave is made of an innovative lightweight fabric designed to provide shade during the day and solar illumination once the sun sets. sleeps in the Israeli city.
“We want to encourage walking and mobility,” says Gaby Kaminsky, managing director of CityZone, an urban innovation center that is a collaboration between the Tel Aviv-Yafo Municipality, Tel Aviv University and Atidim Park, a neighborhood that sees 10,000 people pass through. every day. “If people have to stand in the sun, they will sweat and just won’t. So we have to make the city a tolerable place even in hot weather.
This story is part of Cool Project, a series about the surprising ways cities are reducing heat in a warming world. Read more about the series and the illustrations here.
Despite all of its obvious cooling benefits, shade has often been overlooked by authorities when it comes to reacting to extreme heat. But Tel Aviv, where high summer temperatures can regularly exceed 104 degrees, has highlighted the importance of shade through a number of municipal projects as the world grapples with a rapidly warming planet.
The impact of shadow on the body is unique. It is well established that cities have microclimates called “urban heat islands”, but high air temperatures are not the only cause of heat stress. Research shows that standing in the shade can reduce perceived heat by 15 degrees compared to direct sunlight, significantly mitigating health threats such as cardiovascular and respiratory disorders, heat stroke and even death. . At least 363 Israelis died during heat waves between 2012 and 2020, according to a study by Israel’s Environmental Protection Ministry and Tel Aviv University.
Climate change will lead to more frequent, severe and prolonged heat waves. A study published in the journal Communications Earth and Environment found that 92% of the 165 countries surveyed are projected to experience extremely hot annual temperatures once every two years by 2030 under current national emission reduction commitments. In the pre-industrial era, it was as little as once every hundred years.
Tel Aviv takes these numbers and the role shade can play in mitigating extreme heat seriously. Prior to the launch of LumiWeave, the city developed “shade maps”, which document the shading of public space provided by elements such as buildings, trees, colonnades and pergolas.
According to Or Aleksandrowicz, an assistant professor in the Faculty of Architecture and Urban Planning at the Israel Institute of Technology who led the mapping initiative, the maps allow for rare insight at the street and neighborhood level. “We need more shade, but where and what?” asks Aleksandrowicz, who developed the maps with a small team for several months in 2018 and 2019.
The team used cutting-edge analysis to create an indicator called the Shade Index, which compares shade provision across the city on a scale of 0 to 1. They found classic indicators such as Tree Canopy Cover or Sky ViewFactor. , although easier to calculate at the city level, can distort the daily and annual variance of solar levels. To minimize costs, they also concluded that denser urban areas supplemented by tree planting may be a better approach to urban design than more open spaces, which require many more trees to provide similar levels of d. shadow in the street.
“Trees are something we cherish and want to plant more,” says Aleksandrowicz. “But if you plant them without root space, you’ll have a constant source of problems. Trees require a lot more investment in infrastructure to make room for them.
With Portland’s canopy dwindling, the city ended its street tree planting contract with Friends of Trees.
According to a 2021 report by C40’s Cool Cities Network, accurate mapping of urban trees can be useful not only for mapping shade, but also for understanding the effectiveness of tree planting for climate purposes. . In this regard, Tel Aviv’s shade maps could soon bear fruit: in January, Israel announced that it would plant 450,000 trees in urban areas by 2040 at an estimated cost of 2.25 billion shekels ($676 million).
One problem that Aleksandrowicz’s team highlighted, however, was that they only had 2.5D rather than 3D city-scale mapping of buildings and tree canopies, which which means that the shadow may have been overestimated since it was calculated as maximum during the whole day, regardless of solar orientation. and leaf density. They also called for universal regulations on shade provision which could be used to establish benchmarks.
Sam Bloch, a New York-based journalist who is writing “Shadow,” a book exploring the relationship between shade, climate and inequality, says modern municipalities tend to overlook shade due to technologies such as air conditioning and smart glass that blocks sunlight, as well as the dominance of cars, whose need for wide roads reduces the potential area for sidewalks and gives less space for trees.
“But the shade has this particular value,” Bloch explains. “It’s where people want to be when it’s hot. It maintains common spaces and social ties.
The shadow can also play a role in the fight against inequalities. Bloch says there can be an air temperature difference of 10 to 15 degrees between neighborhoods in the same city due to infrastructure. “There is a distinction between public and private shadow,” he says. “And there is usually shadow poverty in the poorest areas. Cities should react to this. The photo above shows the loss of tree cover in Portland between 2015 and 2020
In various civilizations, the shadow played an important role, according to Bloch. Before the idea of the street tree, the Roman Empire often had arcaded walkways in cities. Historic colonies in the Middle East and North Africa, on the other hand, had very narrow streets, allowing buildings to create shade.
These days, as Tel Aviv leads the way, Bloch says, others are adopting different tactics:
Vienna offers citizens a subsidy to install exterior blinds and awnings; Phoenix turns its black asphalt streets to gray, using a special sealer that reflects rather than absorbs the desert sun; Melbourne supports its shade by recycling gray water; and Singapore has a network of covered walkways for rain and sun protection, as well as regulations stating that at least 50% of public spaces must be shaded during the day.
Back in Tel Aviv, the municipality placed LumiWeave orders for 10 more sites across the city. The fabric, created by designer Anai Green, is embedded with organic photovoltaic solar cells. It requires no electrical infrastructure, saves costs, and can provide nighttime illumination for up to three days without sunlight. But that shouldn’t be a problem as Tel Aviv has an average of around 300 days of sunshine per year.
Alongside LumiWeave, CityZone is working with other Tel Aviv-based start-ups such as SolCold, which has developed a paint – which will be tested later this year – that actively cools when exposed to sunlight, reducing theory temperatures at lower than shade. . BioShade, on the other hand, uses hydroponic systems to grow shade plants up to 10 inches per day, helping to speed up and simplify the process of growing trees.
“We have no time to lose,” says Aleksandrowicz. “We need to use the knowledge we have now for large-scale implementation of shading.”
Peter Yeung is editor of Reasons to be Cheerful. A journalist based in Paris, he also writes for publications such as the Guardian, the LA Times and the BBC. He has filed stories across Europe, Asia, Africa and the Americas.
This article is available for The Oregonian/OregonLive via the Solutions Journalism Network.