Elementary school science teaches us that in the sun, dark colors get hot while white stays cool. Now new research from Lawrence Berkeley National Laboratory has found an exception: scientists have determined that certain dark pigments can stay just as cool as white by using fluorescence, the re-emission of absorbed light.
It is well established that white roofs can help mitigate the urban heat island effect, reflecting the sun’s energy back into space and reducing a city’s temperature under normal weather conditions. In a new study of Guangzhou, China, Berkeley Lab researchers working with Chinese scientists found that during a heat wave, the effect is significantly more pronounced.
A collaboration led by Berkeley Lab scientists has established a method to simulate in the lab the soiling and weathering of roofing materials, reproducing in only a few days the solar reflectance of roofing products naturally aged for three years. Now this protocol has been approved by ASTM International as a standard practice for the industry.
Working with Chinese researchers, Berkeley Lab has conducted the first comprehensive study of cool roofs in China and concluded that they would be effective in substantially reducing energy use and greenhouse gas emissions in climate zones with hot summers.
Looking strictly at the economic costs and benefits of three different roof types—black, white and “green” (or vegetated)—Berkeley Lab researchers have found in a new study that white roofs are the most cost-effective over a 50-year time span. While the high installation cost of green roofs sets them back in economic terms, their environmental and amenity benefits may at least partially mitigate their financial burden.
A recent Journal of Climate paper by Stanford’s Mark Jacobson and John Ten Hoeve (2011) on urban heat islands and cool roofs is a useful contribution to the literature. However, their results regarding white roofs are preliminary and uncertain. Along with work at the Lawrence Berkeley National Lab, other published papers have addressed the broader benefits of white roofs. These studies taken together raise important issues that need to be considered from a policy standpoint to fully understand the potential of more reflective (white or cool) surfaces.
With the aid of rooftop instruments, satellite images, an airplane and a balloon, Berkeley Lab scientists are conducting the first-ever study to determine how pollution impacts the efficacy of white roofs in cooling the planet. The yearlong project in northern India will also be the first to take physical measurements to characterize the cooling and climate effects of white roofs.
A new study from Lawrence Berkeley National Laboratory (Berkeley Lab) breaks new ground by using a high-resolution model of the continental United States that incorporates land-surface feedback to probe the effects of deploying light-colored roads and rooftops. Berkeley Lab researchers Dev Millstein and Surabi Menon found that atmospheric feedback—such as changes in cloud cover or precipitation—does have an important effect, resulting in different amounts of cooling in different cities, but that cool roofs and pavements are still beneficial for combating global warming.
Paris may have the Eiffel Tower and London has its Big Ben, but Lawrence Berkeley National Laboratory has the iconic domed roof of the Advanced Light Source. Now the ALS is getting a new roof—and not just any roof but a cool roof that will reflect sunlight back into the atmosphere, thus playing a small part in mitigating global warming.
Can light-colored rooftops and roads really curb carbon emissions and combat global climate change? The idea has been around for years, but now, a new study by researchers at Lawrence Berkeley National Laboratory that is the first to use a global model to study the question has found that implementing cool roofs and cool pavements in cities around the world can not only help cities stay cooler, they can also cool the world, with the potential of canceling the heating effect of up to two years of worldwide carbon dioxide emissions.