Thomas McKay, representing MRA member PPG, sent the following letter regarding white roofs to Dr. Chu. Nicely done, Tom!
August 31, 2009
The Honorable Steven Chu
Secretary of Energy
U.S. Department of Energy
Dear Mr. Secretary:
I am writing on behalf of PPG Industries to respond to your suggestion that Americans use white roofs on their homes and buildings. While that would certainly save energy and help ease global warming, as you suggest, there is no need to limit roof color choices, particularly if the homeowner or building owner is planning to install a metal roof.
Thanks to a new generation of coatings that reflect the sun’s infrared (heat) energy, architects, building owners and homeowners can now select from a wide range of climate-appropriate metal roof colors, including medium and dark tones, without significantly sacrificing the energy performance associated with white roofs.
According to Solar Reflectance Values (SRV) published by the Cool Roof Rating Council (CRRC), PPG has several colors, including dark evergreen, slate grey and terra cotta red, that are considered “cool” for steep-sloped roofs, according to ENERGY STAR, the CRRC and U.S. Green Building Council. PPG also makes several light-toned colors that meet the criteria for low-sloped or flat roofs.
The color issue is especially important for steep-sloped roofs, which are used most often for residential buildings, where color and design are paramount. Low-sloped roofs are more common to commercial buildings. Since they are rarely seen by the public, there is limited need to provide additional color.
Here’s another important thing to consider: When comparing the SRV of a white roof against that of a dark color, the solar reflectance for the white roof will always be higher (and in some cases, much higher). However, when the heat flux (the amount of energy migrating into a building that must be removed by air conditioning) between the two roofs is measured, the difference is not proportional to their respective SRVs. If you’d like, I can provide a case study by the Florida Solar Energy Center that effectively demonstrates this phenomena.
In addition to color selection and the sustainability of their coatings, metal roofs have a number of critical environmental advantages over competing roofing materials. For instance, metal roofs are completely recyclable at the end of their useful life, which means they can be remade for other applications after their initial service as a roof is over.
Metal roofs also last longer than other materials, such as asphalt shingles, EPDM, TPO and built-up roofs, which are susceptible to cracking caused by temperature-driven expansion and contraction. This durability also enables metal roofs to maintain their original solar reflectance longer than other products because they more readily shed dirt, leaves and other organic materials.
Finally, metal roofs are less expensive and energy-intensive to transport than concrete, cement and clay tiles, which can weigh several hundred pounds or more per square. (Metal roofs weigh about 75 pounds per square.)
As you know, choice and individuality are among the values Americans cherish most. PPG and the roofing industry as a whole are working to give customers the color choice and the energy performance they demand while promoting a healthier, more sustainable planet.
Sincerely,
Thomas McKay
Product Manager
PPG Industries, Inc.
