LA’s new reflective streets send heat back to space


When scientists aboard the International Space Station aim their thermal imagers at Los Angeles, the sweltering red and orange patch looms a crescent of cool bluish-white at the bottom of the San Fernando Valley.

Greg Spotts, director of sustainability for the City’s Office of Street Services (Streets LA), is proud of these wintry-looking pixels – few can say their work is visible from space. In this area, in the center of the Winnetka district of the valley, the pavement was painted with a special reflective coating. “The locations near the cool pavement were, on average, two degrees Fahrenheit cooler than the surrounding area,” says Spotts.

“Previously, our measurements focused on measuring the surface temperature of the pavement itself, which showed a difference of 10 to 15 degrees Fahrenheit in hot weather,” he adds. The thermal satellite camera is important, however, because it shows that the special cooling pavement not only lowers the temperature on the road but “produces a cooler neighborhood” in general.

Ten streets in ten neighborhoods have been treated with this refreshing paint, and the next phase has just begun: This month, bright yellow trucks will be driving through West Hollywood and South LA to spray ten streets with white coating. “We have identified 200 city blocks in eight underserved neighborhoods for the next phase of district cooling.”

The record-breaking heat waves that have scorched the land from Arizona to Antarctica this year will only get worse, and cities, where heat radiates from buildings and asphalt, will take the brunt of it. “We built our cities like ovens,” says Spotts. “We use much of the same materials that we have been using since World War II. We need large-scale change. Highly developed urban areas can experience mid-afternoon temperatures 15 to 20 degrees Fahrenheit warmer than surrounding vegetation areas, according to NOAA. Reducing greenhouse gas emissions is addressing the root cause, but in the meantime cities are looking for ways to lower the temperature. One of the cheapest is to paint roofs and streets white.

The Greek islanders of Santorini, with their whitewashed earth buildings, were onto something: white surfaces can keep a densely populated area cooler. To this end, New York City has added reflective white coatings to more than 10 million square feet of roofs over the past decade. And Los Angeles has installed more than 30 million square feet of cool roofs under its new building code. These days when you visit parts of LA, such as Winnetka or Echo Park, you will notice black asphalt turning to a light grayish white for over 50 blocks.

“At first we thought it might reduce the use of air conditioning and thus help reduce the associated carbon emissions,” says Spotts, “but we’ve learned that the main driver of this work is public health. We are the only city in the United States that records heat-related deaths and emergency room visits in the winter. Although Los Angeles is not the hottest city in the United States (it would be Phoenix) and its climate is tempered by ocean breezes, the heat still carries deadly risks. “We can have hot, humid air in January, and people are not prepared,” Spotts knows. “In the neighborhoods around the northern edge of town, the number of days above 95 degrees (35 degrees Celsius) is likely to double, and they already have 40 or 50 of those hot days each year. Can you imagine having 100 days a year at 95 degrees or higher? ”

Despite all the concerns about worsening hurricanes, floods and tornadoes, the intense heat is killing more Americans than any other weather event. A recent UCLA study found that higher temperatures even increase the risk of injury – researchers estimate that high temperatures already cause about 15,000 injuries per year in California.

In 2015, as part of LA’s Green New Deal, Mayor Eric Garcetti pledged to lower the city’s average temperature by three degrees over the next 20 years. “Cool Streets LA” is part of the effort, piloting six cool neighborhood projects in vulnerable communities by 2021 and ten by 2025, ”says Spotts. Painting the streets is clearly not enough: the main goals include increasing the canopy of trees in the most needy areas by at least 50% by 2028. “Rising temperatures put our local communities first. line of the climate crisis, ”Garcetti said. “Cool Streets LA is all about taking action that will have a real and direct impact on people’s daily lives. “

Spotts, a former New York talent manager who co-founded the Shortlist Music Prize and has been a talent manager for record producers and engineers on projects for Seal, Alanis Morissette and Jewel, enjoys talking with residents who come outside often. to learn about the new pavement. “Each resident says they have noticed that their surroundings are getting hotter and hotter – everyone.” Spotts originally feared residents would complain because dirt and tire marks are more noticeable on the brighter pavement, “but that didn’t happen.” Polls show residents appreciate the program. “It’s cooler,” reads one of their comments. “Now my family and I go out on the weekends, spread blankets in the front yard and spend the time outside… Since the application of cool sidewalks, a lot of people from other neighborhoods are walking in our neighborhood. “

It’s not as easy as laundering everything. The right materials and strategic placement are essential, otherwise a reflective coating can even have the opposite effect. A recent study from Purdue University found that a new ‘ultra-white’ reflective paint is the most efficient – it reflects 98% of sunlight back into space – but it contains a rare mineral and is not. not ecological. Some cold pavements require sufficient resources and carbon-intensive production that their climate benefits are not wiped out. Cost is another issue: reflective paint is around 50% more expensive and probably needs to be reapplied every three to five years. (On the other hand, heat waves are also costly.)

In addition, urban heat is not evenly distributed. Black and Hispanic residents of American cities are almost twice as exposed to urban heat islands. “There are huge equity issues in neighborhoods,” Spotts acknowledges. “These are neighborhoods with overcrowded housing, also often old, unsanitary housing. Spotts uses the Trust for Public Land’s Climate-Smart Cities tool, a conservation organization, to analyze city hot spots, and a Google Earth tree canopy tool. “All the tools have identified the same neighborhoods: 200 blocks where we will be installing cooling pavements over the next ten months. “

He believes district cooling supports three principles at the same time: sustainability, equity and workforce development. “Because if you are dependent on public transport and it’s too hot to get to and wait for your bus stop, you won’t be well prepared for your work day.” Mobility and warmth are now linked. To solve the multiple problems, the “District Cooling Committee” within Streets LA brings together engineers, landscape architects, pavement and tree specialists to find the best approach for what Spotts calls “holistic multidisciplinary thinking”.

LA doesn’t just look at its own territory: the city is associated with places like Phoenix, Tucson and Philadelphia. And 25 US cities have formed a “Cool Road Partnership” to exchange information on best practices, maintenance and costs. “We are trying to leverage the purchasing power of these 25 cities instead of each city according to its own efforts,” Spotts said. “I think this is going to be a game changer in the near future.”

This story was originally published in Reasons to Be Cheerful and appears here as part of the SoJo Exchange of the Journalism Solutions Network, a non-profit organization dedicated to rigorous reporting on responses to social issues.

Michaela Haas, Ph.D., is Editor-in-Chief at Reasons to be Cheerful. Award-winning author and solutions journalist, her recent books include “Bouncing Forward: The Art and Science of Cultivating Resilience,” published by Atria.

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