If you’ve ever had the misfortune of wearing a black shirt or hat in the direct sun, you know how hot and uncomfortable it can get very quickly. Now imagine a black roof on a building that is exposed to this sunlight all day long across a much larger surface area. It heats up the entire building by absorbing much of the sun’s rays.
Black roofs can reach extremely high temperatures, retaining the heat both during the daytime and at night. That can be very significant. So much so, that urban areas can compete with deserts when it comes to hot temperatures. According to Stuart Gaffin, a climate researcher at Columbia University and NASA’s Goddard Institute for Space Studies, “I see surface temperatures in the city that routinely exceed what you might find in the desert.”
NASA uses satellites to record land skin temperature (LST), measuring the temperature of the land surface, which is typically much hotter than the air. NASA has recorded LST measurements of 170 to 180 degrees Fahrenheit on black-tar roofs in New York City during the summer.
The heat from black roofs, as well as other factors – such as asphalt roads, densely spaced buildings, and bus and car exhausts – create what is known as heat islands. These arebuilt-up urban areas that experience significantly higher temperatures than surrounding areas. According to the Environmental Protection Agency (EPA), daytime temperatures average one to six degrees Fahrenheit hotter in urban areas vs. rural ones, and up to 22 degrees hotter at night.
What does all this heat mean? In addition to the critical environmental caused by hotter cities, and the health issues it poses for people, it is very costly for building owners. Air conditioning is a major cause of high energy consumption and costly energy bills.
Are White Roofs the Solution?
Painting roofs white dramatically lowers temperatures. According to the Environmental Research Letters, a white roof in New York City was 42 degrees Fahrenheit lower than a typical black roof. Keep in mind that while white cool paints do reduce roof temperatures, there are sometimes situations where a white roof is less than optimal. For one, acrylic white paints collect dirt easily and typically require regular cleaning and maintenance to retain their efficiency. Even if a building owner repaints the roof, the result is a reduced ROI.
White roofs can also raise concerns about light pollution. A high concentration of white roofs can cause glarefrom the sunlight bouncing off the reflective surface. In addition to potentially bothering neighbors, this reflection can cause problems for aircraft. Some airports have lobbied to ban white roofs because the glare they produce is considered to be dangerous for aircraft pilots.
Dark Cool Coatings Provide Choice
Advances in science now mean there are options other than white roofs. New cool coatings are now available in darker colors that dramatically reduce building temperatures, without the problems of white paint. For example, Nygra’s cool coatings come in a range of colors, and even black or dark colored ones effectively reflect the sun’s rays and reduce temperatures. Some cool coatings, regardless of color, can reduce building heat by up to 40 percent. In addition to roofs, darker coatings mean there are more possibilities for using cool coatings to reduce heat in other facilities such as warehouses, shipping containers, fuel tank farms and more. The range of colors available mean facility exteriors can match a company’s branding or be easily camouflaged for military purposes.
Cool coatings provide a critical solution to the problem of hot buildings and their contribution to heat islands and pressing environmental and health issues that are likely to worsen as the climate continues to heat up. This advanced technology also helps to dramatically reduce energy usage and costs for building owners. So hopefully, we can say goodbye to urban heat islands in the near future as more buildings use cool paints to reflect the sun’s rays while also reflecting their distinct character through a range of colors.