At the EPA, All About Ballast
This is an exciting time to be in the roofing industry. The rebounding economy is driving rising sales, and there is a sense of optimism in the construction business that is making us all feel good about the future.
Part of this optimism is based on what we are learning about our products, and their strengths, especially when it comes to energy efficiency. Our 21st Century research is finding new value in some of the tried-and-true workhorses of the roofing industry.
Ballasted EPDM, for instance, has ranked high for the last forty years as a cost-effective, durable and easy-to-install roofing choice. Today, based on those popular attributes, it accounts for more than a third of EPDM installations. Recently, ballasted roofing has moved into the forefront in energy codes along with the newer-to-market reflective membranes as a “cool roof” that will save energy in warm climates. In fact, the EPA recently updated its ENERGY STAR website, stating that, “ballasted EPDM roofing systems are a very effective means of significantly lowering the roof top surface temperature similar to reflective roofing products.” The initial impetus for the reassessment of ballasted roofing was a study that came out of the Oak Ridge National Laboratory. Researchers there conducted a three year study comparing roofing membranes, and found that the cooling loads for the ballasted systems using concrete pavers, heavy ballast stone, and medium ballast stone were essentially no different than the cooling load for the reflective white system. In other words, a ballasted roof saved as much energy as a reflective roofing system in hot weather.
The folks who establish codes and regulations for the building industry took a look at this research, and probably a second or third look. And then, based on the science and corroborating studies that followed, they incorporated ballasted roofing into their regulations about cool roofing. The city of Chicago, for instance, includes ballasted roofs in its energy code, along with “vegetative garden roofs” and “light color surfaces”, as meeting the standard for a cool, or energy-saving, roof. The California Energy Code now recognizes ballasted roofs to be the equivalent of a cool reflective roof meeting the prescriptive requirements of Title 24. Cool ballasted roofs are included in the IGCC as an alternative to white roofs in climate zone 3.
An important caveat here: as the EPA notes on its EnergyStar website, “. . . please remember the energy savings that can be achieved with reflective roofing is highly dependent on facility design, insulation used, climatic conditions, building location and the building envelope efficiency.” In other words, there are many more factors to consider in designing an energy-efficient roof than the color of the top layer. But the “top layer” is one of the important factors, and ballasted roofs are now being recognized as one of the most energy-efficient choices in the roofing market today.