More unintended consequences of white roofs

In a previous post, White roofs and unintended consequences, I reported on research from Arizona State University that found white roofs decrease precipitation in the already dry desert. Obama’s Energy Secretary Steven Chu once pitched painting roofs white as a solution to global warming. Many people and businesses are installing white roofs to do their part, so they think.

As a result of that post, I was contacted by a representative of a major national manufacturer of membrane roofing systems, mainly for commercial and industrial applications. That company (Carlisle SynTec) produces both dark and white roofing systems. To my surprise, the company spokesman said that while white roofs may keep a building cooler, they nonetheless have some detrimental unintended consequences when used in cool climates. These unintended consequences include:

Elevated rooftop temperatures:

White roofs may keep the roof surface and building cooler, but, the heat has to go somewhere. Heat reflected from white roofs can cause the ambient air temperature above the roof to be hotter than it ordinarily would. That can effect the performance of air conditioning units in two ways. First, the higher temperature of the ambient air causes the A/C unit to work harder, using more energy.


Second, the electrical conduits feeding A/C units become less efficient when temperature rises, according to an article in IAEI magazine, a trade publication for electrical inspectors.

“The interiors of conduits in sunlight, such as those containing conductors feeding air conditioning units on rooftops, become significantly hotter than the outside air (which is always measured in the shade). Data show that these temperature differentials can easily reach 70°F, even when the conductors are electrically unloaded. Remarkably, the differentials were found to be essentially independent of the outdoor temperature all through the range from 70°F to above 100°F.”

“To determine the need for ampacity* corrections, these temperature differentials need to be added to the outdoor temperatures, which reach 90°F or higher in most areas of the USA during the summer months.”

“As might be expected, the temperature differential decreases the further above the roof the conduit is placed. So, for example, when summer temperatures reach 95°F in Chicago, the interior of a conduit lying directly on a roof might be 165°F, while the temperature in a conduit 12 inches above the roof might be 125°F. Interestingly, because light-colored roofs reflect more heat back onto the conduits than dark roofs, their conduit interiors are hotter at heights more than an inch or so above the roof.

*Ampacity: the maximum amount of electrical current a conductor or device can carry before sustaining immediate or progressive deterioration. Ambient temperature and the ability to shed heat affect the ampacity rating.

 Effects on neighboring buildings:

A white roof will reflect heat. If the building with a white roof is surrounded by taller buildings, that reflected heat impinges on neighboring buildings causing them to expend extra energy to keep cool.

Increased Energy Costs:

White roofs keep buildings cooler (depending on the insulation). But, if you are in a northern climate that requires heating in winter, the heating bills will be higher. For instance, the graph below from the Department of Energy’s “Cool Roof Calculator” shows the additional heating expense for white-roofed buildings in Detroit:


Moisture buildup inside roof:

Because a white roof itself is cooler than a black roof, the white-roofed building is more prone to condensation build up inside the roof on winter days.

Maintenance costs:

White roofs have to be cleaned to maintain their cooling effect. If the roof is not cleaned it loses the anticipated benefits.

Will white roofs provide a solution to the phantom menace of global warming? Probably not, but the idea may sound good. A 2011Stanford study, published in the Journal of Climate: “‘Effects of Urban Surfaces and White Roofs on Global and Regional Climate,” estimated that “worldwide conversion to white roofs, accounting for their albedo effect only, was calculated to cool population-weighted temperatures by ~0.02°K but to warm the Earth overall by ~0.07° K.” That study was computer modeling. The results depend on the assumptions, and, as the author say, “the range of uncertainty may be larger than the range of results provided here.” The paper concluded that white roofs may have a small impact on the urban heat island effect, but the impact is too small to affect global warming.

The point of this story is that rather than blindly following a politically-correct, one-size-fits-all eco-fad, do your homework to choose a system that is most efficient and cost-effective for your particular application.

See also some other “great” government ideas:

How Many Haz-Mat Suits Do You Need to Change a Lightbulb?

Compact fluorescent bulbs may contribute to skin cancer

Implications of new vehicle fuel efficiency standards

Renewable energy mandates raise electricity costs

Clean Coal: Boon or Boondoggle?

White roofs and unintended consequences

Obama’s Energy Secretary Steven Chu once pitched painting roofs white as a solution to global warming. Maybe, but new research finds that there are unintended consequences: reduction of rainfall in the Southwest U.S.

Researchers from Arizona State University have found that “warming resulting from megapolitan expansion is seasonally dependent, with greatest warming occurring during summer and least during winter. Among the most practical ways to combat urbanization-induced warming – the painting of buildings’ roofs white – was found to disrupt regional hydroclimate, highlighting the need for evaluation of tradeoffs associated with combating urban heat islands (UHI).” (See press release.)

In a paper published in Environmental Research Letters (see full paper here) the researchers studied possible effects of white roofs on Arizona’s sun corridor (Phoenix, Tucson, Prescott, and Nogales). Note that this is a computer simulation study.

Urbanization, with its tendency to cover natural surface with various artificial surfaces such as asphalt, concrete, and buildings, which reduce natural evapotranspiration causes a reduction in rainfall. Their maximum urbanization scenario leads to a 12% reduction in rainfall. Painting roofs white leads to an additional 4% reduction in rainfall.

The researchers do note: “Integration of highly reflective cool roofs within the built environment offsets about half of urban-induced warming, leading to small regional-scale cooling during the winter season.” But, “the combined effects of UHI-induced warming and evapotranspiration changes act in the same direction and reinforce one another” thereby making the already arid region dryer.

The researchers provide a caveat in the usual scientific jargon: “While we consider our results robust, we recognize the value of a model intercomparison and differing parameterization selection (e.g., incorporation of various convective schemes) that could improve simulated diagnosis of uncertainty quantification.” Translation: we think we are right, but with computer models it’s garbage in, garbage out.

Update: More unintended consequences of white roofs.

See also:

Urban heat island effect on temperatures, a tale of two cities

Warmer nights no proof of global warming

Another Federal Boondoggle?

“Obama’s federal government can weatherize your home for only $57,362 each.” That was the headline in a Los Angeles Times story yesterday, based on numbers from the GAO. Nobel prize wining energy secretary Steven Chu blames government red tape. Who would of thought it? The Energy Department disputes GAO figures.

Read the Story:

Obama’s Science Advisors

In his inaugural speech, President Obama said that “We will restore science to its rightful place…” I took that to mean that policy would be based on good science. In April, he declared that “the days of science taking a back seat to ideology are over.” But instead of the professed ideal, Obama appointed ideologues. His science advisors seem to be large on radical ideology and short on objective science.

Science Czar, physicist John Holdren, Director of the White House Office of Science and Technology Policy, favors some radical cures for global warming and advocated population control. Holdren has proposed, “organized evasive action: population control, limitation of material consumption, redistribution of wealth, transitions to technologies that are environmentally and socially less disruptive than today’s, and movement toward some kind of world government” (Paul Ehrlich, Anne Ehrlich, and John Holdren, Ecoscience: Population, Resources, and Environment, San Francisco: W. H. Freeman and Company, 1977). Also in that book, the authors proposed putting chemicals in the water supply to make women infertile and engineering society by taking away babies from undesirables and subjecting them to government-mandated abortions.

On climate change, Holdren’s long term goal is “equal per-capita emissions rights,” meaning that a country may emit only an amount of carbon commensurate to the number of its persons, not on the basis of its production. For example, the U.S. would be allowed to release only about 20 times as much carbon as Ecuador, although the U.S. produces 144 times the goods and services. (IBD)

More recently, Holdren said that global warmingis so dire, that the Obama administration is discussing radical technologies to cool Earth’s air. He is considering shooting pollution particles into the upper atmosphere to reflect the sun’s rays. “It’s got to be looked at,” he said. “We don’t have the luxury of taking any approach off the table.” (AP) For the past 30 years we have spent billions cleaning up the air. Holdren’s proposal of once again polluting the air logically implies that removing the pollution itself was responsible for global warming, not CO2.

Physicist Steven Chu, Energy Secretary, said, “It is now clear that if we continue on our current path, we run the risk of dramatic, disruptive changes to our climate in the lifetimes of our children and grandchildren,” adding, “at the same time, we face immediate threats to our economy and our national security that stem from our dependence on oil.” (New York Times) See:Your Carbon Footprint Doesn’t Matter for a rebuttal.

Chu recently told the Los Angeles Times that global warming might melt 90 percent of California’s snowpack, which stores much of the water needed for agriculture. This, Chu said, would mean “no more agriculture in California,” the nation’s leading food producer. Chu added: “I don’t actually see how they can keep their cities going.”

And on a Fox News report, April 18, Chu said that Caribbean nations face “very, very scary” rises in sea level and intensifying hurricanes, and Florida, Louisiana and even northern California could be overrun with rising water levels due to global warming triggered by carbon-based greenhouse gases. Note that last December the Royal Netherlands Meteorological Institute, in a country that is very concerned with sea level, reported: There is no evidence for accelerated sea-level rise.

Astronomer James Hansen, director of the Goddard Institute for Space Studies of NASA (and a hold over from previous administrations), said, “The trains carrying coal to power plants are death trains. Coal-fired power plants are factories of death.” Last June, Hansen called for coal and oil company CEOs to be “tried for high crimes against humanity and nature.”

Lisa Jackson, head of EPA, is a chemical engineer. In her first move as EPA chief, Jackson pledged to make science “the backbone for EPA programs.” Really? Why then did the EPA just declare that CO2, a substance vital to all life on Earth, is a dangerous pollutant hazardous to human life and the environment? Where is the evidence? This move is the EPA’s most stupid, and most political; one that will trigger a regulatory maze unlike we’ve ever seen before.

Secretary of State Hillary Clinton’s science advisor, Nina Fedoroff, biologist, (also advisor to Condoleezza Rice) told the BBC that, “humans had exceeded the Earth’s limits of sustainability… We need to continue to decrease the growth rate of the global population; the planet can’t support many more people… There are probably already too many people on the planet.”

To round out Obama’s science team, Carol M. Browner, a lawyer, not a scientist, became Assistant to the President for Energy and Climate Change (Energy Czar). According to a Michelle Malkin article, Browner is a neon green radical who until recently was listed as one of 14 leaders of a socialist group’s Commission for a Sustainable World Society, which calls for “global governance” and says rich countries must shrink their economies to address climate change. Browner was head of the EPA from 1993-2000. On her last day in office, nearly eight years ago, Browner oversaw the destruction of agency computer files in brazen violation of a federal judge’s order requiring the agency to preserve its records. Early in her first term as EPA head, Browner got caught by a congressional subcommittee using taxpayer funds to create and send out illegal lobbying material to over 100 grassroots environmental lobbying organizations. Browner exploited her office to orchestrate a political campaign by left-wing groups, who turned around and attacked Republican lawmakers for supporting regulatory reform.

It seems to me that President Obama is not getting the best of advice. These advisors, while they may have good credentials, seem to have let zealotry overcome sound science.