Infrared-reflective pigments are being incorporated into architectural metal roofing products to allow them to achieve higher reflectivity values, even in darker colors such as black and brown.
The improved reflectivity (for example, black changes from 0.07 with normal pigments to 0.32 with infrared-reflective pigments) can mean a much cooler surface temperature and greater energy savings for the building, allowing building owners and managers to select a sustainable roof without sacrificing aesthetic color choices.
To get 1 point for Sustainable Sites Credit 7.2: Heat Island Effect, the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) green building rating system specifies Energy Star requirements, adding a 0.9 emissivity standard.
For steep-sloped roofs, those with a rise-to-run ratio of 3:12 or greater, a 0.25 initial solar reflectance is required. In most cases, coated metal roofs can easily surpass the reflectivity requirement, and in some cases they can achieve 0.9 emissivity. More often they only achieve an emissivity of 0.85, thereby eliminating them from achieving the LEED point. For low-sloped roofs, those below 3:12, and flat roofs, the LEED reflectivity requirement is raised to 0.65, and the 0.9 emissivity standard is the same.
The Cool Metal Roofing Coalition, an organization comprised of metal industry trade associations, is providing commentary and data to USGBC requesting consideration for a reduction of the emissivity standard to around 0.7, contending that in addition to metal roofing’s energy efficiency when the reflective pigments are incorporated into a system’s design, metal’s long term ability to retain its reflective properties and a low life-cycle cost justify reducing the standard. The 0.9 standard “restricts a building owner’s ability to apply a suitable, long-term roof,” says Greg Crawford, executive director of the Coalition. The emissivity standard of 0.9 “is somewhat arbitrary,” says Andre Desjarlais, program manager for the Building Envelope research program at Oak Ridge National Laboratory, a supporting member of the Coalition. The 0.9 standard “is not defensible, but neither is eliminating emissivity altogether. We’re searching for middle ground.”
ROOFING CONTRACTORS NEEDED IN MULTIPLE STATES!