Department of Energy

Countries Commit to White Roofs, Potentially Offsetting the Emissions of Over 300 Power Plants

April 8, 2011

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I am delighted to learn that India, Mexico, and the United States have signed up to join the Cool Roofs Working Group, announced yesterday at the second Clean Energy Ministerial in Abu Dhabi. This working group was offered as part of the Clean Energy Ministerial, which is a high-level global forum to promote policies and programs that advance clean energy technology, to share lessons learned and best practices and to encourage the transition to a global clean energy economy. Initiatives are based on areas of common interest among participating governments and other stakeholders.

I send my thanks and appreciation to these countries for their leadership in helping to pave the way to a cooler planet. This new initiative, announced yesterday by U.S. Energy Secretary Dr. Steven Chu, will foster international cooperation to promote policies and programs that accelerate the adoption of white roofs to cool buildings, cities and the globe.

My colleagues at the Department of Energy’s Lawrence Berkeley National Laboratory, including the world’s leading expert on cool roofs, Dr. Hashem Akbari, now at Concordia University, and I have been studying the benefits of cool roofs and cool pavements for decades. As our understanding of their benefits expands, I am becoming increasingly passionate about promoting this simple, safe, and affordable way to mitigate the effects of climate change.

Benefits from cool roofs and cool pavements accrue at three different levels:

  1. Building energy savings - Highly reflective roofs, particularly white roofs, lower buildings’ net energy use (cooling savings minus heating penalty) by up to 10 to 20 percent when the building is air-conditioned.[1] On buildings without air conditioning, a white roof can reduce inside temperatures by 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit), making buildings more comfortable and possibly saving lives in extreme heat waves.

  2. Heat island mitigation and public health benefits - Citywide installations of reflective roofs and pavements reduce city temperatures. Studies show that cool building and pavement surfaces, along with the planting of shade trees, can reduce a city’s air temperature by 2 to 4 degrees Celsius (4 to 9 degrees Fahrenheit), in warm months.[2] This reduction not only makes the city more comfortable, but also improves the air quality because NOx and volatile organics cook more quickly into smog on hot days. According to a study of the Los Angeles basin, a combination of lighter surfaces and shade trees could reduce exposure to unhealthy air by 10 percent.[3]

  3. Global cooling - Permanently replacing the world’s roofs and pavements with highly reflective materials will have a cooling effect equivalent to reducing greenhouse gas emissions by 44 billion tonnes of CO2, an amount roughly equal to one year of global man-made emissions.[4] Assuming the world’s average car emits 4 tonnes of CO2 per year, these savings are roughly equivalent to taking all of the world’s approximately 1 billion cars off the road for 11 years. This is also equivalent to offsetting the annual emissions of 700 medium sized coal-fired power plants, operating 6,000 hours per year.[5]

I am happy to report that the world is rapidly awakening to the benefits of cool roofs.

I believe that cool roofs are an important part of the solution to global climate change. They represent low-hanging fruit with multiple co-benefits that are valuable to cities and individuals in both developed and developing countries. To help propel their rapid adoption, I have spent the last year working with other scientists and leaders from the energy efficiency field to launch Global Cool Cities Alliance, a new U.S.-based non-profit organization with the following mission:

Global Cool Cities Alliance is dedicated to advancing policies and actions that increase the solar reflectance of our buildings and pavements as a low or no-cost way to promote cool buildings, cool cities, and most importantly, to mitigate the effects of climate change through global cooling.

GCCA is working with scientists, NGOs, corporations, national governments, and, most importantly – cities – to support rapid global adoption of cool roofs and cool pavements. We look forward to sharing best practices and lessons learned with policy makers engaged in the Cool Roofs Working Group, with the aim of accelerating the adoption of cool roofs and cool pavements as a key component of a clean energy economy.

Dr. Art Rosenfeld is a Distinguished Scientist Emeritus at Lawrence Berkeley National Laboratory and a Founding Board Member of the Global Cool Cities Alliance.

[1] H. Akbari et al. 2009. Global cooling: increasing world-wide urban albedos to offset CO2. Climatic Change Volume 94, Numbers 3–4, 275–286. doi: 10.1007/s10584-008-9515-9

[2] H. Akbari et al. 2001. Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas” Solar Energy Volume 70, Number 3, 295–310. doi: 10.1016/S0038- 092X(00)00089-X

[3] H. Taha. 1997. Modeling the impacts of large-scale albedo changes on ozone air quality in the south coast air basin. Atmospheric Environment, Volume 31, Number 11, 1667–1676. doi: 10.1016/S1352-2310(96)00336-6

[4] Akbari et al. 2009.

[5] J. Koomey et al. 2009. Defining a standard metric for electricity savings. Environmental Research Letters 5. Doi: 10.1088/1748-9326/5/1/014017. See figure 3.