[The Vector] “Cool Pavements” Make an Impact
“Changing surface colors in 100 of the world’s largest cities could save the equivalent of 44 billion tonnes of carbon dioxide – about as much as global carbon emissions are expected to rise by over the next decade,” said U.S. Secretary of Energy, Steven Chu in 2009.In fact, pale surfaces reflect up to 80 percent of the sunlight that falls on them, compared with about 20 percent for dark ones, which is why roofs and walls in hot countries are often whitewashed. An increase in pale surfaces in our urban locations could both reflect more solar radiation away and reduce the amount of energy needed to cool buildings.Professor Chu explains he has been influenced by Art Rosenfeld, a member of the California Energy Commission, who pushed for some new building codes. Since 2005, California has required all flat roofs on commercial buildings to be white. Florida and Georgia are among states that have adopted building codes for white roof installations and more than 75 percent of Wal-Mart stores in the U.S. have them. Dr. Rosenfeld, also a physicist at the Lawrence Berkeley National Laboratory, and two of his colleagues from the laboratory, Hashem Akbari and Surabi Menon, made the calculations found in Steven Chu’s quote above and believe light surfaces can help chip away at energy conservation and global warming issues.Using this very concept, some cities (including those in California) are painting roofs white to reflect heat, conserve energy and reduce the carbon footprint. Another company, Emerald Cities, successfully developed a high performance solar reflective coating for asphalt and cement for the same purpose. The special coating can cool down the surface by up to 50 degrees and reduce smog by 15%, and it also preserves deteriorating asphalt. The product is called Emerald Cities (EC) Solar Reflective Cool Pavement, coined Cool Pavement.
In fact, black asphalt covers 60% of city surfaces and is a silent contributor to heat, smog and CO2. Not only are smog and CO2 an issue, but there is risk for heat stroke in pedestrians, especially in crowded places like theme parks. “Green buildings can never be “zero carbon” until the asphalt portion of a project is addressed,” says an Emerald Cities representative.
Phoenix is a flagship city for Cool Pavement, where asphalt temperatures can easily soar past 200 degrees F in summer. The parking lot at the Duffy Charter School in Phoenix was one of the early resurfacing jobs, as shown in the photo above. Another site is downtown Phoenix, with a new installation up just after Memorial Day 2011 – a 90,000 square foot lot between First, Second, Taylor and Polk Streets. It will help cool the city this summer and will serve to show off the product.
A special launch event for Cool Pavement will take place in downtown Phoenix on June 10th, with speakers, a reception and demonstrations.
In addition, a new “100 Cities Initiative” is also being launched by Emerald Cities for Mayors, City Planners and Project Developers nationwide. Participating cities receive training of local contractors for green jobs, specialized Cool Pavement equipment, complimentary monitoring, Department of Energy seminar and educational materials, publicity & media coverage, aerial photos of completed project and status within the “100 Cities Initiative.”
Emerald Cities spent two years conducting research, developing and perfecting the product through MIT and Lawrence Berkeley National Labs. The nano-engineered concrete technology is the first of its kind for use on roads, parking lots, amusement parks, school yards, cross walks, malls, airports and various public surfaces. It earns LEED credits and can generate carbon offset credits. The product is 1/6 inch in thickness, skid resistant, impervious to UV and is 4300+ psi. While light green is a preferred color, Cool Pavement comes in a number of light colors. There are three application choices: spray on, roller application or smooth squeegee application.
Tests conducted on a major highway in July 2010 proved conclusively that on a 110 degree Phoenix summer day, the surface heat of the road was 209 degrees as compared to 135 degrees with Emerald Cities Cool Pavement – a 74 degree difference.
A senior sustainability scientist at Arizona State University, Harvey Bryan, says it is getting significantly hotter. “It’s a magnitude now of about 12 degrees above our historical nighttime lows. It was very typical to have summer evenings of 78 degrees back in the 1950s. Today we rarely go below 90. I think we’re headed to conditions where we have 100 degrees as our maximum nighttime low.” (Phoenix Magazine. “Phoenix’s Urban Heat Island,” May 2011.) Cool Pavements may be one way to help.
