Enter out in a heat at 100 degrees wearing a black shirt, and you will feel much warmer than if you wear white. Now think of your roof: if it is so dark, it is more enjoying the energy of the sun and radiating this heat inside. If it was a lighter color, it would be as if your house wore a giant white shirt all the time.
This is the idea behind the “cool roof”. Last month, Atlanta joined an increasing number of American cities demanding that the new roofs are more thoughtful. This considerably reduces temperatures not only in a building, but in the surrounding urban environment. “I really wanted to be able to approach climate change in the city of Atlanta with a diversity of tactics,” said Liliana Bakhtiari, member of the municipal council, who is the author of the bill, “because it is much easier to change a local climate than in the world.”
Because cities define their own building codes, they can regulate roofs regardless of the whims of the Trump administration, which aggressively releases climate policies. Experts say that fresh roofs are a simple, relatively cheap and effective way to save people from extreme heat. “I like to say that reflective materials transform the roofs of the problem to power,” said Daniel J. Metzger, principal researcher at the Sabin Center for Climate Change Law of the Columbia Law School. “Cool roofs give owners the power to improve results for health and air quality while saving money on their own energy bills.”
Other cities, including Chicago, Los Angeles and New York, have also placed cool roof prescriptions, but they often cover only flat roofs, as you would see on a commercial building. Atlanta’s order covers all the roofs, although it only forces the new ones to be cooled – it does not force anyone to tear if it is not time to replace. It will therefore take a while for each roof of the city to change, but Atlanta also develops quickly with new constructions. “It will be a kind of gradual response, in progress, but ideally permanent in the increase in temperatures,” said Brian Stone, director of the Urban Climate Lab of Georgia Tech. “It grows Atlanta in one of the most prospective cities.”
The Smart Surfaces Coalition – A non -profit organization that works with cities to promulgate cool roof prescriptions – estimates that the new Atlanta building code will cool the city throughout 2.4 degrees Fahrenheit during summer cutting -edge temperatures, and 6.3 degrees in the city’s warmest districts. It also calculates that over a period of 35 years, the order will result in $ 310 million in energy savings, due to residents which must make their air conditioners work less. “It is a super profitable way to make the city healthier, more competitive, to reduce energy bills and protect jobs,” said Greg Kats, founder and CEO of the Smart Surfaces Coalition.
A fresh roof is a passive technology that continues to work alone. For the flat roof of a commercial building, a simple layer of white paint will do the trick. Manufacturers also make special roof shingles that reflect more sun. Whatever the strategy, cool roofs are not more expensive to install than traditional those, and can even be cheaper. They also extend the lifespan of a roof because there is less wear of the material which extends in the heat, then to contract when it cools.
Like any other city, Atlanta has trouble with the urban effect of the heat island: as a summer day is displayed, the built environment of asphalt, brick and concrete absorbs the heat of the sun. This increases the temperatures perhaps to 20 degrees Fahrenheit above the surrounding countryside, where more vegetation releasing water vapor to cool the air. At night, this stored heat is slowly freed from a city, keeping temperatures abnormally high in the morning.
The urban heat island effect becomes particularly bad in low -income neighborhoods, where there is generally less trees coverage than in richer areas. “These people get the triple blow,” said Mark Conway, a member of the council who sponsored the Baltimore roof order. “Not only is it warmer in these regions of the city, but also, they do not have the trees and the shadow to help them, and they cannot pay for AC.”
The effect of the urban heat island becomes very dangerous during heat waves that extend several days, because human bodies cannot take a break at tireless temperatures. Stress is built and built, especially in danger which suffers from asthma and heart disease, because the body tries to pump more blood to refresh itself. Infants and the elderly are also more at risk because their bodies do not cool as effectively than others. As a result, extreme heat kills twice as many people in the United States every year that hurricanes and tornadoes have combined.
Although putting more air conditioners in more houses will help save lives as cities become warmer, it is not a remedy. On the one hand, the units use a lot of energy, and the Atlanta residents already treat some of the highest energy charges in the country, which means that a significant proportion of their income goes to electricity bills. Second, air conditioners actually aggravate urban heat: they work by extracting the heat from the indoor air and pumping it outside – which is why you feel a hot air explosion if you walk by one of them. And if the grid decreases because too many people manage their AC and other devices at the same time, everyone is now much more at risk. “When a house loses power, if its only intervention to stay cool is air conditioning, it is very likely that people inside this house overheat quickly,” said Grace Wickerson, principal climate and health director at the Federation of American Scientists, a non -profit reflection group.
At the same time, American cities complete fresh roofs with more trees – Cleveland, for example, set a goal of obtaining all its residents 10 minutes walk from a green space by 2045. The trees provide shade and also release the steam of cooling water, such as rural vegetation. Parks and gardens also absorb rainwater, preventing floods. “There is just a long litany of good reasons to plant as many trees as possible, and fresh roofs do not withdraw,” said Metzger. “They work together to cool the city overall.”
