In an effort to reduce energy use in buildings and to mitigate the warming effects of climate change, the Cool Roofs and Pavements Working Group formed as a subgroup within the Global Superior Energy Performance Partnership (GSEP) at the second Clean Energy Ministerial in April 2011. Through activities such as demonstration projects, the development and sharing of best practices, research to refine the understanding of the potential of cool roofs and pavements to mitigate the urban heat island effect and global warming, and promoting the inclusion of cool roofs and pavements in building codes, the Working Group advanced policies and actions that increase the solar reflectance of urban surfaces.
About Cool Roofs and Pavements
Roofs and pavements cover 60% of urban surfaces, and they are generally dark in color. As a result, they typically absorb more than 80% of sunlight and then convert that energy into heat. The result is that roofs and pavements contribute to the heating of buildings and cities and thus further exacerbate the warming effects of climate change.
A low-cost, quick-payback solution to this problem is to coat roofs and pavements with materials that reflect much of the incoming sunlight. Such cool roofs can be white or other "cool colors"—conventionally colored tiles that are manufactured to have a higher solar reflectance. It has been shown that cool roofs in temperate or tropical climates absorb approximately 80% less sunlight than dark roofs, and keep buildings much closer to ambient temperatures.
Research suggests that cool roofs and pavements would bring the following significant benefits:
- Cooler buildings: Highly reflective roofs can reduce the indoor temperatures of buildings by 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit), which lowers their cooling needs and thus results in cooling energy savings of approximately 10% to 20% on the floor under the roof. Cool roofs often yield net energy cost savings even after adjusting for a small winter "heating penalty." Cooler indoor temperatures can make unconditioned buildings more comfortable and productive.
- Cooler cities: Studies show that widespread installation of cool roofs and pavements can reduce summer air temperatures in cities by 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit). In addition to leading to a more comfortable environment and a reduction in peak electricity demand, cooler cities provide health benefits, as smog (ozone) forms more quickly at higher temperatures. Cooler cities are also more resilient during extreme heat events.
- Cooler planet: It is estimated that deploying cool roofs globally would have a cooling effect that would offset the warming from 31 billion tonnes of heat-trapping carbon dioxide (CO2). Including pavements extends that to offset the warming from 57 billion tonnes of CO2. That is nearly double the global CO2 emissions in 2012 of 31.6 billion tonnes.
In addition to these benefits, cool roofs are often a low-cost, quick-payback option. Depending on the kinds of materials used, the incremental cost of choosing a cool roof over a more traditional dark roof for a commercial building is approximately USD$0 to USD$2.20 per square meter, which is USD$0 to USD$0.20 per square foot. When factoring energy savings into the equation, the incremental cost can be fully recovered in many applications over a period of 0 to 6 years.
How it Works
White roofs or cool roofs in temperate or tropical climates absorb approximately 80% less sunlight than dark roofs. Source: www.globalcoolcities.org.
The GSEP Cool Roofs and Pavements Working Group collaborated at the local, regional, national, and multinational levels to accelerate development and deployment of cool roofs and pavements. Where feasible, the Working Group sought to incorporate cool roofs and pavements into existing programs, protocols, and organizations. Working Group activities can be grouped into four areas:
- Demonstration Projects
Conducting pilot deployments of cool roofs on low-income homes to demonstrate efficiency and thermal comfort benefits, improve government housing programs, and support skill set development for builders
- Workforce Development
Conducting capacity-building sessions on cool roof deployment with technical experts and establishing training centers and certification programs to develop a cool surface workforce
- Standards, Codes, and Market Infrastructure
Developing standards and codes for cool roofs and creating cool surface materials testing laboratories to enable product labeling and increase consumer confidence in cool surface products
- Information Exchange
Conducting studies on the energy savings potential of cool roof deployment to inform policy development and sharing other information and policy relevant resources, for example, through the Cool Roofs and Pavements Knowledge Base (http://coolrooftoolkit.org)
The Cool Roofs and Pavements Working Group benefited from the participation of the national governments of India, Japan, Mexico, South Africa, and the United States. Additionally, a number of non-governmental partners played critical roles.