The Maryland Energy Administration does not provide any financial incentives to install cool roofs now, but spokeswoman Devan Willemsen said that might be about to change. If lawmakers approve the funding, the state energy office is preparing to roll out a new competitive energy-efficiency grant program targeting low- and moderate-income households, and one of the upgrades the program would pay for is a cool roof.

"We're definitely in support of cool roofs," Willemsen said.

The Abell report also urged the city's school system to integrate cool roofs into its planned $1.1 billion overhaul of 40 school buildings.

Lighter-colored roofing materials went on about 20 city schools that have been renovated or weatherized, the report says. But those crushed-granite and ceramic materials don't yield the same energy savings a true cool roof would.

Keith Scroggins, chief of facilities for the city school system, said administrators are looking at cool roofs, as well as "green" roofs, those which have vegetation planted on them to absorb rainfall and control storm-water runoff.

"As we get closer to design of the first group of schools, we expect to decide on a variety of energy efficient options," Scroggins said.

With storm-water control a priority in Baltimore because of the Chesapeake Bay restoration effort, some might think green roofs would take precedence over cool roofs. Shickman said it's a false choice, as both can go on larger buildings, and with smaller structures the runoff controls can be installed on the ground.

The biggest problem with cool roofs, experts warn, is they can cause or worsen moisture damage if not properly insulated and ventilated.

Stanford University researchers also have suggested that cool roofs might actually warm the planet if they went global, because they'd reflect sunlight back into the atmosphere and warm the many fine particles floating in the air. That's a distant worry for now because cool roofs are nowhere near widespread.

Peterson, an area vice president of the Patterson Park neighborhood association, said she put leased solar panels on her roof first, as a hedge of sorts against rising electricity rates, then had the cool roof installed. It was part of a $3,000 complete energy retrofit of her drafty home, she said. Technicians sealed up cracks, put in additional insulation and installed a new hot-water heater.

The payoff: electricity bills of $100 to $120 for her 1,000 square foot home even with her central air running.

"That is pretty wonderful," Peterson concluded.

Tim.wheeler@baltsun.com

An earlier version misstated the size of Leigh Peterson's home. The Sun regrets the error.

Cool roofs

Designed to reflect sunlight and have lower temperatures than traditional black or dark roofs.

Though many are white, they can be other colors as long as they include reflective material.

Ideal for flat or gently sloped roofs, best when put on new or replacement roofs.

Two basic types: "elastomeric" roof with a multi-layer liquid coating, reinforced with mesh, or prefabricated membrane sheet.

Can reflect up to 80 percent of sunlight, reduce air-conditioning costs by up to 20 percent.