Unsettled science: Faulty science said white roofs atop any building would save energy and decrease CO2. New science finds white roofs in northern and central climates result in greater energy use, more CO2, and waste money. LEED program still uses false science-Philly.com

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6/29/2015, "'Green' roofs not always the most energy-efficient," philly.com, Craig A. Tyler

"Five years ago, Philadelphia City Council passed a green building code requiring that white roofs be used on certain buildings because they are more energy-efficient and help reduce air pollution.

New York and Chicago have similar codes. But the white-roof craze is based on old and faulty research that has promulgated two myths - that these roofs save energy atop any building and that they decrease global warming.

Philadelphians should be concerned that the city is wasting money on energy and possibly causing more, not less, global warming.

There is a significant heating penalty associated with using white roofs in central and northern climates, where owners use three to five times as much energy to heat their buildings than to cool them. In cities like Philly, white roofs consume more energy, which means they cause more cardon dioxide emissions.

A study by Arizona State University shows that white roofs can deflect sunlight into the atmosphere, changing cloud cover and reducing rain. A study by Stanford University simulated what would happen if all the roofs in the United States were converted to white and found that the sunlight reflected by white roofs causes heat to mix with black and brown soot particles to further warm the atmosphere.

Yet this green myth continues. Architects and builders started specifying white roofs 15 years ago, when the U.S. Green Building Council established a new green standard known as Leadership in Energy and Environmental Design (LEED). Today, more than 18,000 professionals nationwide hold LEED credentials, more than 1,000 of them in the Philadelphia region.

The LEED certification system has done a lot of good by recognizing building projects for their environmental quality. It also has influenced public policy, provided important educational opportunities, and generally made cost-efficient, energy-saving buildings a reality across the nation.

But as new studies like those mentioned emerged, architects, builders, and others involved in sustainable construction realized there is a flaw in the LEED point system. By using white roofing materials, they could earn a point for helping a city like Philly stay cooler and therefore lower air-conditioning demand and natural-resource consumption for electricity generation. But the fact that they would spend more on heating costs was not always factored into the equation.

At least the Environmental Protection Agency acknowledges that energy savings provided by white roofs are highly dependent on location and climate. The agency recommends using the Department of Energy's roof savings calculator to determine if the heating penalty exceeds the cooling benefit.

I used the calculator for a 75,000-square-foot building in Philadelphia to compare a white roof with a black roof. Given a certain level of insulation and energy pricing, a three-story building that size would lose $636 annually in energy costs. A one-story building would lose a whopping $2,200.

The LEED program would be strengthened by limiting the point for white roofs to urban settings in southern climates, where cooling demand outweighs heating demand, not in cities like Philadelphia.

Until such a change is made, architects and builders unfortunately will be encouraged to design and build facilities that use more energy than they should and that also may increase carbon dioxide emissions and global warming. Architects and building owners in Philadelphia can act on this new information to improve the environment by limiting the use of white roofs in northern climates while we wait for LEED to change." via Hockey Schtick

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"Craig Tyler is a LEED-certified architect employed by Carlisle SynTec, a manufacturer of white, tan, gray, and black roofing in Carlisle, Pa. craig.tyler@carlislesyntec.com" 


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