Painting roofs white promoted as way to fight global warming
White roofs can save a lot of energy in Costa Rica too....
NEW YORK — Herb Van Gent points his infrared gun at a square of still unpainted
gray shingle and clicks the trigger. He gets an immediate temperature reading:
143 degrees and rising.
Then he aims it 5 feet away to a square of roof I have just painted:
98 degrees and decreasing. He smiles.
"A 45-degree difference and we're only on the first coat," he says.
That means it also will be cooler inside the building, he says, saving energy.
Its 11 a.m. and we are on the roof of a New York retirement home,
rolling out a thick, shiny white paint. Van Gent is one of a volunteer
group that has come up here to paint the roof as part of a city-sponsored
"cool roof" program.
The idea of painting roofs white is catching on across the USA;
Energy Secretary Steven Chu has said it could contribute to the fight
against global warming.
"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,"
said Chu in July, while announcing that Department of Energy buildings would
be painted white wherever possible.
ECO-FRIENDLY:
While white roofs keep homes cool in summer by letting less heat in, they have
little impact on winter heating bills, according to the Cool Roof Rating Council,
a non-profit group created in 1998 to research and implement the technology.
That's generally because the sun is less intense in winter, the group said, and
less important as a heat source. The roofs do not let any more heat escape than
other roofs, it said.
In Arizona, cool roofs are mandatory for state and state-funded buildings, while
Philadelphia has an ambitious green energy plan that put cool roofs at its center.
In New York, with Mayor Michael Bloomberg's blessing, the Department of
Buildings and other public and private groups have vowed to paint 1 million
square feet of roof on city-sponsored community buildings. Organizers have
advertised on Craigslist for volunteers, promising that the painting is
rewarding and fun.
I decided to give it a try.
There were half a dozen volunteers on the roof that day from Wayne, N.J.-based
GAF Materials, which supplied the reflective white paint. Among them was
technical specialist Steve Hecht, who showed me how to spread the paint.
"This should bring the temperature down 50 or 60 degrees," Hecht said as I
rolled a coat onto one small part of the roof.
Proponents say the idea is as sound for private homes as it is for big,
residential apartment buildings. The Cool Roof Council provides information on
materials and resources at its website, Coolroofs.org.
Philadelphia recently held a "cool roofs for free" competition, and a block of
row houses won.
"The biggest difference is definitely when we wake up in the morning," said
Terry Jack, who organized her block's winning entry. "I noticed the difference
the very next morning after they painted the roof. It was a good 15 degrees
cooler inside; it was much more livable."
Workers are painting the roofs on both sides of her street with reflective white
paint, and also insulating the houses. City officials hope to show that a white
roof will reduce the amount of air conditioning used, saving energy and reducing
electricity bills.
According to former California energy commissioner Arthur Rosenfeld, an average,
1,000-square-foot roof painted white can save 10 tons of carbon dioxide, the
equivalent of emissions from one car for about 2 years. On a national scale,
turning roofs cool could eliminate 2 billion tons of carbon dioxide, roughly the
same as taking 20 million cars off the road for 20 years, according to Rosenfeld,
who carried out his experiments with Hashem Akbari at the Lawrence Berkeley
National Laboratory, in California.
So far, many cities have been limited in their response. New York's 1 million
square feet of white roofs is a "very, very, very, conservative target," said
Akbari, who advised the city on its NYC Cool Roofs project.
"When you consider that a large box store or mall can have a roof of 200,000
square feet, the entire New York program is the equivalent of painting five of
those stores," he said.
But Akbari stressed it's not just about white paint.
"Certainly, the white color helps, especially if it's special reflective paint,
but ultimately we want to see people using cool roof material when they have to
change their roofs," he said. "There are a whole range of materials that can
reflect the heat."
Sophisticated white roofing material can lie underneath a roof's visible surface,
he said, reflecting the sun's heat while allowing a wider choice of colors on
the surface.
"Definitely, aesthetics has held back the cool roof movement until now, but that
is changing. You have a longer lasting roof without having to look bad,"
said Akbari.
According to the Department of Energy, there are no federal tax credits for roof
coatings, but there is a tax credit for using cool materials when replacing a roof.
Date published: 17 September 2010
