Green Inside, Outside and Above: Green and Cool Roofs

Apr. 15, 2011 | 0 Comments | Civics | Science | Social Studies | 9-12 | Sustainability

Lesson Steps

Warm-up: Green Roofs in Chicago
     1. Have students read the article from the Christian Science Monitor, Reproducible #1- “With grants and other incentives, Chicago leads the nation in installing green roofs.”

     2. Students should read the article and answer the questions listed below and in Reproducible #2- Article Reflection Questions independently. After all students have completely finished reading and answering questions, have them organize themselves in partners or small groups to share answers.

     3. Have students share their answers with the class in a general discussion about why green roofs are important and any other issues your students are interested in talking about. Ask the following questions:
               a) What are the benefits of green roofs?
               b) Are green roofs a modern invention?
               c) Why do you think Chicago is subsidizing the cost of green roofs?
               d) What are some famous buildings that have green roofs? Have you ever been to any buildings with green roofs? Where?
               e) What is the Urban Heat Island Effect?

Activity One: Urban Heat Island Effect
     1. As the earth is warming, its cities are warming even faster. Tell students that most urban areas have a temperature that is 10°F higher than surrounding areas. Since most of the world’s population lives in cities, we need to be very concerned about this situation.

     2. Have your students brainstorm with their partner reasons why cities are warmer than more natural landscapes. Solicit students to share responses to class.

     3. Explain that trees and vegetation provide natural shading and cooling by filtering the air. Since urban areas are covered in man-made structures and not green life, the natural air conditioning that plants provide us with is lost. The buildings and pavement in a city automatically absorb more heat than any sort of vegetation because of the materials and colors that we choose to build with. Additionally, waste heat released from engines and machinery (cars, air conditioning, factories, etc) heats up the city even more.

     4. Have your students brainstorm on their own why this effect might be harmful to humans and the natural environment. Share with the class that most importantly, the heat island effect amplifies a city’s energy needs. This causes both an economic burden, and a further drain on our earth’s resources. The increased heat also intensifies smog problems and can be a health hazard.

     5. Ask your class if they have any examples of how the Urban Heat Island Effect has affected their lives. Green roofs are really necessary in a city not only because they will cool it down, but because they provide green spaces in a place where concrete and metal are unnaturally commonplace. The elevated temperature in the city is yet another reason why urban life can be more difficult than life in the suburbs.

     6. Green roofs also have other benefits including providing a habitat for plants, insects and other wildlife, reducing runoff, and filtering pollution from water. Although it seems that environmental activism might make more sense in a place where there are trees and natural spaces, it is really more necessary in cities, where people are less connected with the earth but often more threatened by their environment.

Activity Two: A Rainbow of Roofs

     1. According to the EPA, 90% of the roofs in the U.S. are dark colored. Your students should know that dark colors absorb heat from the sun. Black, the most common color of a rooftop, absorbs red, yellow, green and blue light and reflects almost no light. This absorbed light is transferred into heat energy, making black rooftop temperatures reach up to 190 degrees Fahrenheit. This increases cooling costs in buildings and contributes to the Urban Heat Island Effect.

     2. White, on the other hand, reflects all the colors of light that black absorbs, making it a much better color to use if you want things to stay cooler; including the visible, infrared, and ultraviolet wavelengths on a scale of 0 to 1.

     3. Albedo, or solar reflectance, is a measure of a material's ability to reflect sunlight. An albedo of 0.0 indicates that the surface absorbs all solar radiation, and a 1.0 albedo value represents total reflectivity. Although roofs covered with vegetation are one alternative to a dark rooftop, another solution is to find a material with a higher albedo than a conventional black roof. These are called “cool roofs” and are becoming more popular alternatives. This activity is designed for students to practice their researching skills and get a broader idea about what alternatives there are to conventional roofing.

     4. Split your students up into several teams and assign them each one type of “cool roof” to research (besides a conventional green roof). Some options include metal, white paint, tar and gravel, and red/brown tile. Also, one group should research the type of roof that your school has. Have them fill out Reproducible #3- Worksheet for cool roofing research, and then prepare the information for a presentation to the rest of the class. Have the students prepare their topics together, and then have a discussion about which options might be the best for your school, for a home, or for a commercial building.

Activity Three: Cooling Down YOUR School!

     1. Now that your students are knowledgeable about green roofs, they should begin to consider what type of roof their school has. What benefits could a green roof bring to the educational environment at your school? A green roof on your school would have the same economic and environmental benefits as discussed earlier in this lesson, but could it offer more? The plants and wildlife on the roof could be an outdoor classroom for science lessons and other classes. Lunchtime or school events could be held on the roof, and school clubs could use it for various activities. If an intensive green roof is able to hold produce, then your environmental club could manage the gardens and sell the produce. Furthermore, a green roof would serve as a physical reminder of your school’s commitment to environmental innovation and to a greener future and set the example for other institutions in your area to take action.

     2. Public and private high schools, middle schools and universities around the nation have chosen to invest in green roof technologies for these reasons. In May 2005, the Calhoun School (a private K-12 school in NYC) installed a Green Roof on the top of their building. The roof has been used as an herb garden for the cafeteria and is also used for biology classes. The space has been used for art installations, receptions, and has earned the school a number of awards. Mission San Jose High School replaced their gravel roofs with smooth-tops ones covered with white acrylic elastometric coating. These new “cool roofs” helped to reduce heating and cooling costs and helped their old building comply with California’s regulations for energy efficient buildings. Carnegie Mellon University has installed green roofs in four locations around campus.

     3. If all these places have explored greener roofing options, then yours can too. Have your students brainstorm what type of roofing option might be the best for your school district. Please refer to Earth Day Network’s Green Roofs Student Action Plan. There you can find more information about what green roofs are, why they are good for your school, and how to convince your school to get one.

Wrap Up: Roof Discussion
Ask students to name the different types of roofs they have learned about in this lesson, and how their characteristics determine the amount of heat they absorb or reflect. Discuss the importance of green roofs and how they could improve buildings in their communities. Encourage advocacy for green roofs in their neighborhood and at school, and discuss steps that they can take to become involved. Ask your students if they would be interested in pursuing a campaign to get a green rooftop at your school.

Extension: Raise the Roof! Student Roof Campaign
For homework, have your students draft a letter to your school principal or the president of the school board explaining why your school should get a green roof. This should be a convincing formal letter that draws together information that was reviewed in this lesson plan and/or Earth Day Network’s Green Roofs Student Action Plan. Students may include outside research if they need statistics for their letter. This assignment should be assessed not only on the accuracy of the content of the letter, but on grammar, style, and fluidity of the letter. Using these letters as a foundation, have the students select the one(s) that best reflects their interests, or draft an official letter from the entire class, and deliver to the principal or school administrators.