The Case for Reflective Roofs

“Think Global, Act Local” may be a cliché, but it is perfectly applicable to the retrofitting market. Even for the smallest buildings, retrofitting is a local project with global implications. Building improvements that enhance sustainability and efficiency also provide benefits to the local, regional and global community in which the building exists.

This principle especially applies to the case of installing reflective roofs during a retrofit. Reflective roofs keep roof surfaces cooler by reflecting solar energy rather than absorbing it as heat. Combined with insulation, reflective roofs can deliver significant energy savings by reducing the demand for air conditioning on hot days and nights. According to Lawrence Berkeley National Labs, the improved energy efficiency from reflective roofs could save U.S. commercial building owners more than $700 million each year and is typically the primary reason owners decide to install them.

Combining the many individual decisions to put on reflective roofs is how we create a whole that is greater than the sum of its parts. A city with predominantly reflective roofs can be 4 to 5 degrees F cooler than it would be with predominantly dark roofs. Four to 5 degrees may not sound like much, but research shows that energy consumption and poor air quality rise only slightly as temperatures rise, up to a threshold temperature (often around 75 F) and then increase drastically with every degree above that threshold. Once a city hits its threshold temperature, even cooling by a fraction of a degree translates into real dollars and improved health. A study by Lawrence Berkeley National Lab found that the healthier air and reduced energy consumption made possible by cooler city temperatures could cut health-care costs, lost time from work and energy costs by $10 billion a year.

Reflective roofs also help when cities are facing heat waves. Studies of the 1995 Chicago heatwave, which claimed more than 700 lives, found that the most significant contributing factors to mortality were building related—what floor the person was living on, the presence of air conditioning, and whether the building had a dark roof. Currently my organization, the Global Cool Cities Alliance, is studying this connection to learn how many lives could be saved during heatwaves if U.S. cities had more reflective roofs and vegetation.

Climate studies undertaken by a number of different institutions during the last 10 years show that the reflective roof you install has an immediate impact on global warming, as well. These studies find the cooling effect of reflecting solar energy out of the atmosphere cancels the warming effect of greenhouse gases in the atmosphere. By installing reflective roofs where it makes economic sense to do so, we could offset the warming effect of 500 coal power plants worth of greenhouse gases over the life of the roof. That is equivalent to the emissions of half of the world’s cars.

A reflective roof is a good choice when seeking energy efficiency or simply making an unconditioned space more comfortable and productive. It just so happens that it also is a great thing for your neighbors, near and far.