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L.A. is painting its streets white to keep the city cool

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NexusMedia

abor Day weekend delivered record-breaking temperatures to California, as a heat wave swept the state, fanning the flames of the largest wildfireLos Angeles has seen in decades. The unusually warm weather bears the mark of climate change, which is fueling record heat around the globe.

While politicians elsewhere waffle on climate change, officials in Los Angeles are tackling the problem head on with a radical plan to lower the temperature of the city. Mayor Eric Garcetti intends to cut the average temperature in LA by 3 degrees F over the next two decades. As part of that effort, LA streets are getting a new coat of paint.

Cities are prone to overheating, thanks to something called the urban heat island effect. Cities tend to be short on trees, which provide shade, and they are covered with black pavement, which absorbs heat from the sun. Think of how it feels to wear a dark shirt versus a white shirt on a sunny day. A black shirt absorbs light, heating you up. But a white shirt reflects light, keeping you cool.

Densely populated cities tend to be warmer than surrounding areas. Source: Heat Island Group, Lawrence Berkeley National Laboratory

Densely populated cities tend to be warmer than surrounding areas. Source: Heat Island Group, Lawrence Berkeley National Laboratory

The average temperature in a city of a million or more people can be more than 5 degrees F hotter than surrounding areas. That extra 5 degrees can turn a hot day from uncomfortable to deadly. As temperatures rise, cities will be an especially dangerous place to be during a heat wave, as sweltering weather threatens heat exhaustion, among other maladies. To protect public health, city officials are going to make the city cooler.

As part of that effort, Los Angeles is coating its roads in CoolSeal, a gray paint that keeps streets and parking lots 10 degrees cooler than black asphalt. Engineers developed the material for military air bases to keep spy planes cool while they rest on the tarmac. This can help them avoid being detected by satellite-mounted infrared cameras, which measure heat.

la street service

CoolSeal will help Angelinos save money during the summer, when air conditioning sends power bills soaring. And it will save lives by lowering temperatures and improving air quality. Hot weather worsens air pollutionby turning car exhaust into smog, which can make life miserable for people with asthma and other respiratory conditions.

Of course, LA will have to do more than paint over a few streets to cool off the city. Angelinos will also need to plant more trees and apply white paint to rooftops — at least those not already covered in solar panels. While LA is a pioneer of reflective streets, other cities, like New York, are already experimenting with reflective roofs or, like Melbourne, lowering the temperature by planting trees. LA is hardly alone in its effort to stay cool.

“This is an urgent challenge, and it’s much bigger than one person,” said Mayor Garcetti in a recent statement. “Climate change is a fact of life that people in Los Angeles and cities around the world live with every day.”


Jeremy Deaton writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture. You can follow him @deaton_jeremy. Mina Lee contributed to this report.

Source: NexusMedia. Reproduced with permission.  

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  • Joe

    When I look at the new suburban residential developments in the outer South West Sydney the thing that strikes me most is the ‘blackness’, black tiled roofing and black bitumen roads. And the streets and yards are treeless deserts. Talk about dumbass. No wonder they all need A/C in summer.

    • Rod

      I’m not sure if you can blame the buyer or builder but just plain stupid.
      Council’s could mandate cool roofs. The 3 new row houses next to me all have black tin roofs and no sisalation under the tin. No wonder their ACs are going all night long.

      • Hettie

        Yep. It’s a no brainer. As well as keeping your house cooler in summer, a white roof, by reducing radiation of heat, keeps it warmer in winter. As much as 3 degrees Celsius each way.
        That can be 30% of your heating and cooling costs.
        And every white roof or street does its little bit to compensate for the loss of the reflective polar ice.

      • Chris Fraser

        AC all night long ? Most likely they have lots of block, or brick, walls.

        • Rod

          They are a bit of an environmental disaster. All attached row houses. No Northern sun. Too much East West (unshaded) glass. They do have a concrete slab. Hebel cladding. Not sure if that is a positive or negative.

  • Bill Holliday

    It’s true! Try it:- take a sheet of galvanised iron and paint one half of it white using any old white paint (but it should look white, not cream or another light colour). Place the gal iron in the sun for half an hour and feel the temperature difference between painted and unpainted sections.

    • Coley

      Surely pure ‘white paint’ compared to “cream or another light colour” would only make a marginal difference?

    • ClimateWarriorMelb

      Assuming you’re talking about new gal iron, wouldn’t the shininess/reflectivity of the gal coating be something like the white? Or is it more absorptive than it looks? I can understand it as it ages though,as the zinc oxidizes and becomes quite dull.

      • Bill Holliday

        Coley: I suppose it depends how “light” the colour is.
        Considering that the human eye can only perceive a narrow section of the sun’s spectrum, perhaps the best approach would be to paint bands from every old tin of paint from the shed and then compare the temperatures achieved.
        ClimateWarriorMelb: new gal iron quickly dulls. If one has to use gal iron rather than Colorbond then perhaps sheet your roof and then paint later. The dull gal iron apparently offers better paint adhesion anyway.
        One type of paint (e.g. one variety of Dulux Weathershield) doesn’t need any primer – just paint straight on the gal iron after washing down with detergent-water.

  • Ron Horgan

    Have you ever walked along a nice new white concrete driveway with white walls on both sides. With full summer sun the heat and glare are overpowering.
    Sure this will reradiate the heat and light and cook the poor people in the street.

    • brucelee

      Or sand, or even water, you get cooked by reflection.
      This is progressive, but more of a band-aid

    • Joe

      Only mad Englishman stroll outside in the Aussie midday summer sun

    • Chris Drongers

      Think it through Ron – white reflects, a large fraction in the visible wavelengths. Glare.
      Black absorbs heat, and light. Both heat and absorbed visible light raise the temperature of the black bitumen, roof etc. The hot bitument/roof then re-radiates the absorbed energy as heat, Infra-red radiation which heats up people, other buildings and is absorbed by the atmosphere. Everything gets hotter.

      A ‘smart’ roof or other surface which selectively emits radiation in bands to which the sky is transparent minimises the heating by absorbed energy that is re-radiated. Most ‘smart’ roofs are white but some materials are effective in other colours. Colorbond has a range of these colours.

      • Ron Horgan

        I guess that its a question of thermal inertia? The black road absorbs heat during the day and releases heat during the night. The white road should store much less heat as reflection is higher. Think of the desert which swings from the extremes of heat in the day to freezing cold at night.
        For human comfort the black road scene may be better. White roofs but black roads? Use the roads for collecting and storing heat energy?
        My comment was based on actual experience.
        I like the idea of smart surfaces which will radiate in bands to which the sky is transparent.
        At the nano scale there are surfaces which are 100% absorbent and which do not reradiate. The laws of physics look different down there!

        • Chris Drongers

          The measured heat island effect suggests that black roads, black roofs, and lots of concrete raise temperatures during the day as well as at night.
          And people often run airconditioners at night so raising night time temperatures is also undesirable

          • Ron Horgan

            Sure the city buildings are a heat trap and running the ACs dumps extra loads into the atmosphere.
            The contrast is with my back garden where trees and shrubs contain an envelope of cool air on the hottest days.

          • Chris Drongers

            i take your point. rip up half the width of suburban and other non-arterial roads and plant trees. I’ll support that.

          • Ron Horgan

            Cables strung between the trees with pulleys , walking is so 2017?

          • Chris Drongers

            No, walking is so this century. Driving everywhere is so last century.

          • Ron Horgan

            Hi Chris, I just tripped over one of your smart roofs. Stanford Uni Packard Elec Eng have developed Sky Cool Systems which has been modelled to save 20% of AC power use.
            “Cooling system works without electricity” Science Daily5 Sept .
            Great stuff.

  • Greg Hudson

    The same applies to cars. I once had a black car (which is a color choice that seems to be in vogue ATM) and it was the worst color choice I ever made (inside temp was unbearable in the Aussie sun). Never again would I buy a black or dark colored car. WHITE is the new black.
    Last weekend I saw a house with a white colorbond roof, which was the only one I have seen for years. It is a sea of black/charcoal roofing tiles where I live (Doncaster, NE Melbourne)

  • ClimateWarriorMelb

    Anyone got any indications of how expensive this paint is?
    And how much it might be expected to increase the life of the bitumen road (due I would guess to both better sealing / resealing, and less deterioration due to intense heat)?