White caps: Coating roofs in white lowers building temperatures, energy costs

Being cool is a matter of wearing
the right coat.

Dave Alden applied the fashion
axiom to the roof of three low-rise
office buildings he manages in
Walnut Creek for financial services
giant Wells Fargo & Co.

By Marc Albert – BUSINESS
WRITER

The white acrylic coat reflects heat and light instead of absorbing it. That
translates into energy savings, which means money. “The reflective coating
does a super job,” said Alden, regional manager for Northern California
administrative buildings for Wells Fargo & Co.

“It reduces the heat load tremendously,” he said, estimating the coating
cut the daytime roof temperature an average 42 degrees. It cost $1.70 per
square foot, including a 15-cent state rebate, to install cool roof coating on
the roofs of three low-rise Wells Fargo & Co., office buildings in Walnut
Creek.

A cooler roof means less heat penetrates the building to warm interior air –
air that gets cooled by pricey electric power. The system appears to work.

“Before, we had to operate three pieces of equipment first thing in the
a.m.,” Alden said. Now it’s “noonish,” before a second air conditioner is
turned on, he said.

Cool roofs are one of several initiatives that were lent added seriousness by
the energy crisis of 2000-2001. While probably not the most exciting or
largest energy saver, cool roofs cut electricity usage when it counts – at peak load, midday hours.

To encourage commercial building owners to switch to white coatings, the state sweetened the
pot with subsidies.

Cool roofs also reduce so-called “urban heat islands” – microclimates caused by heat-absorbing
tar roofs and asphalt that radiate heat, raising temperatures.

Still, the technique is no panacea. Some professionals fear cool roof materials don’t last and may
prove uneconomical in the long run. A cool roof can run anywhere from about $1.50 per square
foot installed for the simplest spray on coating jobs to $5 per square foot for an entirely new cool
roof.

Experts also admit cool roofs won’t provide much bang for the buck on high rises, or on most
homes.

There also is a wide variation in products. Roof coatings – painted on – are cheaper to buy and
install, about $1.50 to $2 per square foot. Membranes – sheets of material rolled out and tacked,
nailed or glued down – tend to last longer but cost between $2.50 and $5 per square foot. There
are exceptions to both rules, and figuring out which system is most cost-effective generally
depends on the type and condition of the existing roof.

What works also depends on who you ask.

“Obviously, the guys who sell membranes want to sell more membranes, the guys who sell
coatings want to sell more coatings,” said Dan Varvais, a consultant for Placerville-based Applied
Polymers.

As of July, California has installed or has on the books 44 million square feet of cool roofs,
according to Rob Schlichting, spokesman for the California Energy Commission.

“That should save the equivalent of 15 megawatts of electricity, enough to power 15,000
homes,” Schlichting said, referring to peak load capacity on a typical hot summer day.

It doesn’t sound like much compared to the 2,301 megawatts generated by PG&E Co.’s Diablo
Canyon nuclear power plant. But the idea is reducing peak load – those hot days when the
multitudes seek air conditioned relief and draw enough power to threaten blackouts.

The difference is on top. Roof temperatures can be 82 degrees higher than air temperatures on
an ordinary black gravel roof, according to a study by the Lawrence Berkeley National Laboratory.
Some cool roofing materials cut that figure to as little as 9 degrees.

The impact depends on the scale.

Varvais advised the Homebase home improvement chain on roof repairs for it’s 83 stores. A
particular roof’s condition dictated what kind of fix he recommended.

“Sometimes it is better to let a roof wear out, and plan on replacing it in two or three years,”
and sometimes a repair job is in order, Varvais said.

On top of the $0.15 subsidy per square foot, tax advantages can guide a decision. Roof repairs
can be written off as a one-time charge against income, while a new roof can be amortized over
40 years, Varvais said.

Varvais is a believer. He said roof temperatures on a Sacramento elementary school dropped
from 172 degrees before installation to 103 degrees after.

“There was a significant reduction in the heat gain going into the building,” he said.

Government scientists say cool roofs benefit air quality. Dark, energy trapping roofs actually help
raise temperatures in surrounding areas. A concentration of dark roofs and asphalt pavement –
typical of urban and suburban landscapes – lift temperatures, creating so-called “urban heat
islands.”

Scientists say ground-level ozone, a component of smog, more easily creates smog at warmer
temperatures.

Officials from the California Energy Commission estimate the average energy savings per square
foot of cool roof at about 0.4 kilowatt hours a year.

According to PG&E, basic commercial electricity rates range from 12 to 14 cents per kilowatt hour.
The savings works out to roughly 5 cents per foot per year.

A kilowatt hour is a unit of electricity equal to the amount needed to light ten 100-watt light
bulbs for an hour. Officials said the rebate is necessary to encourage the new technology.

“The one thing about the roofing industry, people are afraid to try something new,” said
Virginia Lew, a California Energy Commission engineer. And the jury is still out on many products.

Some roofers have learned a wait-and-see attitude. They say new products frequently don’t
perform or last as promised. “New products come out and make a lot of money for the first few
years and when problems come out, (the manufacturers) file for bankruptcy,” said Jack Pickerill,
president of Livermore-based J. Pickerill Roofing Inc. Pickerill says a majority of his customers
prefer “tried and true” products.

“I like for something to be out a year or more before I get involved in it. I don’t want to be a
guinea pig,” Pickerill said. One roofer also said products sold in California, meeting state
requirements limiting volatile organic compounds, may not stick as well, and thus may not last as
long.

Patching or replacing a flaw in a new roof would probably wipe out the economies provided by
rebates and energy savings. Experts said roofs can last from as little as two years up to as long
as the building itself, with proper maintenance. Some materials are damaged by puddles of water
forming on a roof that fails to drain. Other products lose their efficiency when they get dirty, so
cleaning is key.

Cool roofs for residential homes remain elusive. Because they are typically sloped instead of flat,
most products designed for the large typically flat-roofed commercial buildings don’t work. White
coatings and membranes also face consumer resistance because of the color.

Another issue is efficiency. Cool roofs deliver their lower interior temperatures during midday –
precisely the time most homeowners are at work five days a week, making them less likely to
lower the air conditioning control knob when it gets hot.

Homes can qualify for the rebate, but only if they already have an air conditioner.

Experts said cool roofs combined with evaporative “swamp” coolers, ceiling fans, and broad leaf
trees can mitigate much of the need for air conditioning – even in very hot areas. Broad-leaf trees
can shade windows in the summer, keeping out the heat, but drop leaves in the fall, allowing
winter light in.

Still, residential cool roofs are far from ubiquitous. Lisa Gartland, a consultant at Oakland-based
Positive Energy and a cool roof proponent, said she is having an ordinary roof installed on her
home because she couldn’t find a cost-effective cool residential alternative. Still, the commercial
applications are promising.

Alden, the Wells Fargo manager, says he expects the $1.70 per square foot Wells paid installing
the cool roofs will pay for itself in three to four years. Alden said energy consumption for the
three buildings this July was 20 percent lower than the previous year. The company also installed
energy saving T-8 lighting.

Alden said the company’s goal is cost cutting. On some properties, Wells is replacing old air
conditioning units with more efficient ones. “Overall we have a 16 percent, 20 percent reduction
in (electricity) consumption in Northern California,” Alden said.

Marc Albert can be reached at (510) 208-6414 and [email protected]

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