'Smart' roof can read the thermometer and save energy in hot and cold climates

Washington, March 22 : A team of scientists has developed a 'smart' roof coating, made from waste cooking oil from fast food restaurants, that can 'read' a thermometer and save energy in hot and cold climates.

The coating automatically switches roles, reflecting or transmitting solar heat, when the outdoor temperature crosses a preset point that can be tuned to the local climate.

Roofs coated with the material would reflect scorching summer sunlight and reduce sticker-shock air-conditioning bills.

When chilly weather sets in, the coating would change roles and transmit heat to help warm the interior.

"This is one of the most innovative and practical roofing coating materials developed to date," said Ben Wen, leader of the research project, and the vice-president of United Environment and Energy LLC in Horseheads, New York.

"This bio-based intelligent roof coating, compared with a traditional cool roof, could reduce both heating and cooling costs as it responds to the external environment," he said.

"It will help save fuel and electricity and reduce emissions of volatile organic compounds from petroleum-based roofing products. In addition, it will provide a new use for millions of gallons of waste oil after it is used to cook french fries and chicken nuggets," he added.

Scientists already have evidence that "white roofs" — roofs that are painted white to reflect solar heat and help cool buildings during peak summer weather — could significantly reduce global warming by lowering fuel consumption.

However, white roofs can have a wintertime heating penalty because they reflect solar heat that would help warm the building.

So white roofs are a benefit in summer, but a detriment in winter.

The new "intelligent" coating may sidestep this quandry.

Tests on coated asphalt shingles showed that it could reduce roof temperatures by about 50 - 80 percent in warm weather.

In cooler weather, the coating could increase roof temperatures up to 80 percent compared with the traditional cool roof.

By changing the coating's composition, Wen and colleagues can tune the substance, so that it changes from reflective to transmitive at a specific environmental temperature.

"Even though the roof temperature is reduced or increased by a few degrees, depending on the outside temperature, this change could make a big difference in your energy bill," Wen noted.