How do you cut down on Heatwaves?

In 1995 a massive heat wave hit Chicago, bringing temperatures to a blistering 41˚C (106˚F)! Over 700 people died from the high temperatures, a statistic that may have been preventable. On average, Chicago is about 1-degree Celsius (2 degrees Fahrenheit) warmer than the rural areas around it, but it can get hotter by as much as 13-degree Celsius (21 degrees Fahrenheit). There is no way to predict when a heat wave will strike next, but Chicago has started taking steps to combat that kind of heat.
Chicago's City Hall is covered with plants.
(©TonyTheTiger/Wikipedia)

Greening the Roofs

Since 1995 Chicago has increased the amount of green space in the city not only by planting trees but also by building green roofs. Green roofs aren't just roofs that are painted green; they are actually living gardens that are planted on top of buildings. Chicago has nearly three times the amount of green roof space than any other city in the country. Chicago's City Hall has one of the biggest and most beautiful green roofs of them all. The garden spans 23,000 square feet and has more than 100 plant species. Besides looking pretty, this green roof has a lot of other benefits. Since the green roof was put in, Chicago estimates it has saved City Hall about $3,600 a year in heating and cooling bills.

A view of a green roof garden on top of a building in Chicago.
(©Conservation Design Forum/Wikipedia)

How can plants help save thousands of dollars in energy? Plants absorb sunlight and use it during photosynthesis. They don’t radiate the energy back out as heat like conventional roofs do. Plants also use the energy from the sun in a process called evapotranspiration. During evapotranspiration, some of the water that the plant has absorbed through it roots evaporates through its leaves. Since this process takes energy from outside the leaf to occur, it ends up cooling the air around the plant.

A bed of flowers, including black-eyed susans, sits atop a skyscraper in downtown Chicago.
(©Diane Cook, Len Jenshel/National Geographic)

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  • absorption

    noun

    A type of transfer where a substance takes in another substance or energy.

  • conservation

    noun

    The protection of something in the natural world.

  • evapotranspiration

    noun

    The transfer of water from plants into water vapor in the atmosphere.

  • mitigation

    noun

    The process of limiting the impact of something.

  • preservation

    noun

    The action of taking care of or protecting something.

  • sequester

    verb

    To take in or isolate something.

  • atmosphere

    noun

    A layer of gas that surrounds the surface of a planet.

  • erosion

    noun

    The movement of broken down, or weathered, material.

  • greenery

    noun

    Plants or vegetation

  • photosynthesis

    noun

    The process plants use to make food from sunlight, carbon dioxide, and water.

  • radiate

    verb

    To give off energy, such as heat, in the form of waves.

  • storm water

    noun

    Excess water from a storm the ground cannot absorb quick enough.

  • concentration

    noun

    A relatively close cluster of objects.

  • evaporation

    verb

    The process a liquid goes through to change into a gas.

  • habitat

    noun

    The natural environment of an organism.

  • pollutant

    noun

    A substance that is considered to be unnatural or undesired in the environment and can cause harm to plants or animals.

  • runoff

    noun

    Water from rain or snow that flows over the surface of the land.

  • vegetation

    noun

    Any and all plant life found in a particular area.