A study monitoring three generic white membranes within New York City that represent a cross section of the dominant white membrane options for US flat roofs: (1) an EPDM rubber membrane; (2) a TPO membrane; and (3) an asphaltic multi-ply built-up membrane coated with white elastomeric acrylic paint. The paint product is being used by New York City’s government for the first major urban albedo enhancement program in its history. We report on the temperature and related albedo performance of these three membranes at three different sites over a multi-year period.
The results indicate that the professionally installed white membranes are maintaining their temperature control effectively and are meeting the Energy Star Cool Roofing performance standards requiring a three-year aged albedo above 0.50. The EPDM membrane shows evidence of low emissivity; however this had the interesting effect of avoiding any ‘winter heat penalty’ for this building. The painted asphaltic surface shows high emissivity but lost about half of its initial albedo within two years of installation. Given that the acrylic approach is such an important ‘do-it-yourself’, low-cost, retrofit technique, and, as such, offers the most rapid technique for increasing urban albedo, further product performance research is recommended to identify conditions that optimize its long-term albedo control. Even so, its current multi-year performance still represents a significant albedo enhancement for urban heat island mitigation.
S R Gaffin et al (2012). Bright is the new black—multi-year performance of high-albedo roofs in an urban climate. Environ. Res. Lett. 7 014029 doi:10.1088/1748-9326/7/1/014029
Marc Imhoff (National Aeronautics and Space Administration (NASA))
Reza Khanbilvardi (NOAA-CREST Center at City College of City University of New York)
Angelica Pasqualini (Center for Climate Systems Research, Columbia University)
A.Y.Y. Kong (Center for Climate Systems Research, Columbia University)
Danielle Grillo (New York City Department of Buildings)
Adam Freed (New York City Mayor’s Office of Long Term Planning and Sustainability)
D. Hillel (Center for Climate Systems Research, Columbia University)
E. Hartung (Center for Climate Systems Research, Columbia University)
Source: Environmental Resources Letters
Publication Date: December 2011