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Global Superior Energy Performance Partnership (GSEP)

Working Groups:

Cool Roofs and Pavements Working Group

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 will advance policies and actions that increase the solar reflectance of urban surfaces.

About Cool Roofs and Pavements

Roofs and pavements cover 60 percent of urban surfaces, and they are generally dark in color. As a result, they typically absorb more than 80 percent 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 replace roofs and pavements with more-reflective materials that would reflect more sunlight than their dark counterparts. 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 percent less sunlight than dark roofs, and keep buildings much closer to ambient temperatures.

Impacts

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 percent 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 would result in health benefits, as smog (ozone) forms more quickly at higher temperatures. Cooler cities are more resilient during extreme heat events.
  • Cooler planet: It is estimated that increasing the earth’s reflectivity by 10 percent by adopting cool roofs and surfaces in hot climates would have a cooling effect equivalent to reducing greenhouse gas emissions by 44 billion metric tons of carbon dioxide over the 20-year life of the roof (2.2 billion metric tons annually). That is the rough equivalent of either eliminating global anthropogenic emissions for more than a year or taking 1 billion cars off the road for 11 years.

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 US$0 to US$2.20 per square meter, which is US$0 to US$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 zero to six years.

How it Works

White roofs or cool roofs in temperate or tropical climates absorb approximately 80 percent less sunlight than dark roofs. Source: www.globalcoolcities.org.

Illustration on how cool roofs work

Temperature readings of a cool roof versus a normal roof

Activities

The GSEP Cool Roofs and Pavements Working Group will collaborate at the local, regional, national, and multinational levels to accelerate development and deployment of cool roofs and pavements. Where feasible, the Working Group will seek to incorporate cool roofs and pavements into existing programs, protocols, and organizations. The Working Group has identified four objectives:

  1. Collect information and tools of existing Working Group partners in an accessible repository, and draft case studies and best practices of cool roof and pavement development efforts, including partnership models, code development, incentives, and financing
  2. Promote cool roofs and pavements and identify or develop champions to drive development and implementation, with a focus on city leaders and market makers
  3. Develop projects with partners to demonstrate the efficacy of cool roofs and pavements to the public, policy makers, and the private sector
  4. Provide technical assistance to develop infrastructure for testing, rating, and ongoing research at the local and regional levels by nationally recognized laboratories using international standards

The Working Group is pursuing these objectives in three primary thematic areas:

  1. Improving the thermal comfort of affordable housing through the inclusion of cool surfaces in new construction and retrofits
  2. Supporting the development of cool material product testing, rating, and certification procedures and protocols to facilitate effective building codes
  3. Facilitating knowledge sharing of cool pavements research

Where appropriate, the Working Group will track progress and share information on the public information portal that is being developed as part of the Clean Energy Solutions Center.

Request for Governments

Governments currently participating in the Cool Roofs and Pavements Working Group include India, Japan, Mexico, and the United States. Together, these countries include 8 of the 20 largest cities in the world. The Working Group would welcome the participation of additional governments.

As the benefits of cool roofs and pavements differ across climates—with the greatest benefits reaped in warmer climates—it is proposed that each interested government convenes a panel of local scientists and other technical experts to evaluate the benefits of cool roofs and pavements in its particular geography. The United States can provide technical assistance to these panels. Depending on the findings of its assessment and on its interests and other circumstances, a government can then identify Working Group activities in which it would like to engage.

Resources