With all the talk about global warming, do cool roofs make sense in the Rocky Mountains, given that we usually think of Colorado as more of a heating climate? Colorado contains four distinct climate zones. Among Colorado’s climate zones are areas 5B and 4B, which are along the Front Range and Eastern plains of Colorado. In these zones we experience warmer temperatures from late May through the middle of September. Therefore, there are several seasons when cool roofs obviously make sense. But what exactly are cool roofs?
According to the Cool Roof Institute, “A cool roof reflects and emits the sun's heat back to the sky, instead of transferring it to the building below.” “Coolness” is measured by two properties, solar reflectance and thermal emittance. These values are used to calculate the solar reflectance index (SRI)—the higher the number, the better on a scale of 1-100.
The principal behind cool roofs is to save energy on cooling buildings down. Along the Front Range where the majority of the population of Colorado lives in cities such as Denver, Colorado Springs and Ft. Collins, we experience some 300 days of sunshine. That many days of sunshine which can be a welcoming heat source in the winter, can also be a drain on the cooling loads in the other seasons. Those familiar with the LEED rating systems: Note that a minimum SRI of 78 on most flat commercial roofs is required.But what about the SRI numbers on residential roofs? The minimum SRI for 2:12 or greater roof pitches is only 29.
Throughout the last several decades, many Front Range cities grew with wide spread sprawling suburbs and thousands of roof tops, all of which absorb the radiation of the sun. According to a cool roof calculator that compiles energy savings on the average residential home, a single level home of 2500 square feet may experience a savings of $425 and up per year. Now if you multiply that figure by thousands of homes the energy savings can be staggering, let alone the impact to the environment to help cool the planet.
Manufacturers such as Owens-Corning use the cool roof technology in the shingles they manufacture. Owens-Corning also recycles old asphalt shingles, which is a plus for recycling, global warming and reducing our carbon footprint in Colorado. This company manufactures in Denver, Colorado which equals less transportation costs. Before you re-roof your home, consider looking into a shingles that have higher SRI’s. The polar bears will thank you for generations to come.