1. Sponsors: National Aeronautics and Space Administration (NASA) NASA Goddard Space Flight Center (GSFC) NASA Goddard Institute for Space Studies (GISS) NASA New York City Research Initiative (NYCRI) NSF Research Experience for Undergraduates (REU) Contributors: Stuart Gaffin, Ph.D., Cynthia Rosenzweig, Ph.D. Alan Roditi, High School Teacher Nicolette Nunez, Undergraduate Student Nicholas Hoffman, High School Student Sunscreen for the City: Using White Roofs to Combat the Urban Heat Island Effect Nicolette Nunez, Nicholas Hoffman, and Alan Roditi Abstract Background Surface Temperatures: Tow Pound Causes of Albedo Loss Climate change is an increasingly detrimental problem, causing a significant rise in global climate temperatures; scientists are investigating using high albedo surfaces as a heating mitigation strategy. A major cause of UHI is the low albedo, or reflectivity, of urban surfaces. Albedo is measured from 0 to 1, and urban areas tend to have albedos 2-5% lower than those of the surrounding areas (Jin et al., 2005). NYC’s Mayor Michael Bloomberg and US Secretary of Energy Steven Chu are taking an active interest in these initiatives. Through the NYC ºCool Roofs governmental program, over 5.5 million square feet of NYC rooftops have been ‘cooled’, which involves painting the roofs white. Cool, reflective white roofs can potentially mitigate UHI, decrease summer temps, lower cooling costs by over 20%, and improve air quality (Akbari, 2009). Our results indicate a staggering 67ºF difference between our freshly painted white control patch and the initial black asphaltic rooftop. The 1-year aged roof also retains a 47ºF difference between it’s surface temperature and the surface temperature of the asphalt. Air Temperature on the cooled roofs were similar to the air temperature in Central Park at the approximately same time. In our study, we focused mainly on evaluating the effectiveness of the NYC ºCool Roofs Program, which uses white elastomeric acrylic paint to cool rooftops. We took surface and air temperature readings on three NYPD building sites throughout the summer. Most rooftops in NYC are colored black and therefore have a very low albedo. The term albedo is used to describe how much visible light and radiation a surface reflects. It is evaluated on a scale of 0 to 1 where 0 is completely absorbing and 1 is completely reflecting. Black roofs typically have an albedo of 0.1, whereas white roofs typically have an albedo of 0.7. Using Thermoworks Infrared Sensors, we took surface temperatures of black asphalt, 1-year aged white, and fresh white roof surfaces. Our results should show that the temperature of the fresh white control patch is 20º F lower than the aged white surface and 67º F lower than the black asphalt surface. Experimental Setup Fresh and 1-year aged white roof temps were significantly lower than the asphaltic surface. Fresh white surface was slightly lower than the 1-year aged white surface. Maintenance is necessary to maintain high albedo, although aged surface is still much lower than the asphalt surface. Future studies include: Using advanced Flir Thermal Imaging cameras for complex visual analysis of surface temps. Long term comparison of aged white surfaces to fresher white surfaces Surface Temperatures: Precincts Ponded rainwater white surface (dirty spot on aged white roof) approximately 30ºF lower than black asphalt surface. Fresh white surface approximately 30ºF lower than ponded rainwater spot. Positive correlation between albedo loss and higher surface temperature. Areas Used for Analysis: 10 ft ×10 ft fresh white control patch Ponded rainwater area left on aged roof Black asphalt surface coned off Surface Temperature readings were taken using Thermoworks IR Infrared Sensors every minute. For an average surface temperature of the 1-year aged white surface, readings were taken every 5 feet around the surface area of the roof. Strong positive correlation between white paint surface and black asphalt surface. Tow pound air temperature similar to Central Park air temperature at same time on same day. Fresh white control patch 67ºF lower than black asphalt surface. 1-year aged roof 47ºF lower than black asphalt surface Fresh white surface temp quite close to Central Park air temp Ponded Rainwater (dirty) area approx. 20ºF warmer than aged white Aged white surface on average 30ºF cooler than typical asphalt surface temp Albedo slightly lower than fresh paint, but still cools surface temp Ponded Rainwater (dirty) area is nearly exact temp as asphalt surface 2-year aged white surface is warmer than 1- year aged white surface indicating albedo loss 2-year aged white still approx. 20ºF cooler than asphalt Conclusions and Future Work References Akbari H., Levinson R., Rainer L. (2005). Monitoring the energy-use effects of cool roofs on California commercial buildings. Energy and Buildings, vol. 37, 1007-1016. Akbari H., Menon S., and Rosenfeld A. (2008) Global cooling: increasing world-wide urban albedos to offset carbon dioxide. Climatic Change, vol. 95, issue 3-4. Gaffin S. R., Rosenzweig C., Eichenbaum-Pikser J., Khanbilvardi R., and Susca T. (2010). A Temperature and Seasonal Energy Analysis of Green, White, and Black Roofs. Columbia University, Center for Climate Systems Research. New York. 19 pages. Jin M., Dickinson RE., and Zhang D., (2005), The footprint of urban areas on global climates as characterized by MODIS, American Meteorological Society, 1551-1565. Ridgwell A., Singarayer J. S., Hetherington A. M., and Valdes P. J. (2009). Tackling regional climate change by leaf albedo bio- geoengineering. Current Biology, vol. 19, issue 2, 146-150. Woodward I. F., Bardgett R. D., Raven J. A., and Hetherington A. M. (2009). Biological approaches to global environment change mitigation and remediation. Current Biology, vol. 19, issue 14, 615-623. The white roof at the NYPD 38 th St Tow Pound was painted in 2013 through NYC Cool Roofs. Materials White elastoacryllic paint Thermoworks IR- Pro Professional Infrared Sensors Air Probe Umbrella