Cities have a growing concern for what's called the urban heat island effect, citing studies that show excess heat generated by the structure of the city—human activity and the presence of dark, impermeable surfaces—traps heat within the city and raises its temperature in comparison to the surrounding rural areas. White roofs are being push-ed as a way to combat this effect.
“There's been concerns throughout various larger cities in the U.S. that these darker surfaces—be it the road, the parking lot or the roof—contribute to elevated temperature in those cities,” Henegar said. “They felt the easiest way to try and attack some of that is by mandating the use of white roofs in those locations.”
The Global Cool Cities Alliance is a non-profit founded in 2010 that works with cities around the world on understanding the issues around urban heat islands. It works with cities to identify whether or not it has a heat island and how big it is, and it connects the city to experts in the industry to develop strategies to help mitigate that heat island.
According to Executive Director Kurt Shickman, the most economical of those options is cool roofing.
“At the end of the day, you have to make a building-by-building decision in terms of design and what's going to work on an individual building,” Shickman said. “Generally I think cool roofs are the best choice for cooling down a city, reducing the AC load in a building and helping to reduce the amount of surface heat on or being blown off the roof. But my organization doesn't advocate for turning everything white as soon as possible. We want the buildings to be designed well and to meet what we think is an important social and environmental goal for cities.”
Unfortunately for the ERA, regulatory bodies do not share Shickman's philosophy. Department of Energy Secretary Stephen Chu said in 2010 that cool roofs are “one of the quickest and lowest cost ways we can reduce our global carbon emissions and begin the hard work of slowing climate change.”
At the same time, Chu and President Obama committed to reduce its greenhouse gas emissions 28 percent by 2020. Chu directed all DOE offices to install cool roofs when constructing new roofs or replacing old ones on DOE facilities, whenever cost effective.
With the federal government taking the lead, other cities have followed suit, even those in the northern climates.
“There is certainly concern among manufacturers, JM included, that legislation brought to light too fast may not offer the best solution for people in those regions,” said Rick Gustin, product manager for EPDM at Johns Manville Inc.
Chicago was ahead of the curve. The city implemented an ordinance in 2008 requiring most new roofs and roof renovations to use white reflective materials. The ordinance was updated to include ballasted roof systems.
New York City recently strengthened its building code to require expanded use of white roofing material. It also established the NYC CoolRoofs Initiative, a program that paints black roof surfaces with a white reflective paint designed to help reduce energy use.
While white roofs are not required by the state of Pennsylvania, they are beginning to gain traction in Pittsburgh. The Children's Museum installed a white roof in 2004 as part of a museum expansion program, and earlier this year the city launched its own cool roofs program to paint the surfaces of 10 city-owned buildings with reflective paint.
Mike DuCharme, director of product marketing at Carlisle Syntec, doesn't think paint programs make sense in the northern climates. He cited a study that demonstrated a higher degree of moisture accumulation among white roofs in northern climates when compared to black EPDM counterparts. If all things are equal, changing the coating of the roof changes the dynamics of the building.
“What was working might not now work with that same building,” DuCharme said “Maybe it has enough humidity within the building that now you start to get condensation when you didn't have it before. You go from the one that was performing with good energy efficiency to one that has saturation insulation, poorer energy efficiency and maybe a premature roof failure.”
Thorp said if facility managers want to change the color of a roof, they must take into account the number of occupants, type of insulation and the assembly.
“We want the decision of what roof to use to be a joint decision between the building owner, the facility manager and the architect or the designer,” Thorp said. “Those are the people who should be making the decision about what sort of roof system to use.”