White roofs reduce surface temperatures more than 40 degrees compared to black roofs, study finds
Retrofitting a black roof surface to white reduced peak rooftop temperature in New York City by 43 degrees Fahrenheit, on average, during the summer of 2011, according to a new study published online at Environmental Research Letters. The study was the first long-term effort in New York to test how specific white roof materials held up and performed over several years.
Widespread installation of white roofs, through the NYC CoolRoofs program, could reduce city temperatures while cutting down on energy usage and greenhouse gas emissions, said Stuart Gaffin, a research scientist at Columbia University. The options tested in the study included two synthetic membranes requiring professional installation and a white-paint coating that is being promoted by the city's white roof initiative.
The reflectivity and emissivity of the professionally installed white membrane coverings held up remarkably well after four years in use, the study found, while the painted surfaces were degraded after two years.
Several white roof membrane products that require professional installation are available for commercial facilities with flat roofs. Two of these options and a white-paint coating that is being promoted by the city's white roof initiative were tested in the study.
At Duro-Last, we applaud the results of the study. However, readers should be aware that there is a wide variety of choices available in cool roof materials.