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Cool Roofing… Cutting Through the Glare

Cool Roofing… Cutting Through the Glare. May 12 & 13, 2005 Atlanta, Georgia. Cool Roofing… Cutting Through the Glare. Sponsored by Roof Consultants Institute Foundation (RCIF) Oak Ridge National Laboratories (ORNL) National Research Council of Canada (NRC) Attended by

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Cool Roofing… Cutting Through the Glare

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  1. Cool Roofing… Cutting Through the Glare May 12 & 13, 2005 Atlanta, Georgia

  2. Cool Roofing… Cutting Through the Glare • Sponsored by • Roof Consultants Institute Foundation (RCIF) • Oak Ridge National Laboratories (ORNL) • National Research Council of Canada (NRC) • Attended by • Over 200 construction and design professionals • Industry media & trade associations • Presented by • 30 researchers from universities, government, industry

  3. Cool Roofing…Cutting Through the Glare Key Symposium Topics • Environmental Issues • Economic Issues

  4. Cool Roofing…Cutting Through the Glare Cool Roofs & the Environment • Highly reflective roofs can reduce urban temperatures in the summer…. • Reducing ozone formation • Reducing energy costs • Reducing fossil fuel demand

  5. Cool Roofing…Cutting Through the Glare Cool Roofs & the Environment • ….. but the cooling effect of highly reflective roofs may be overstated • Wind effects not always considered • Degradation due to roof aging not fully addressed • Alternative approaches not always considered

  6. Cool Roofing…Cutting Through the Glare Cool Roofs & Wind Effects The Effects of Wind on Roof Surface Air Temperature No Wind With Wind Effect Added 31 29 27 25 23 Air Temperature (oC) 0 10% 20% 30% 40% 50% 60% 70% 80% Roof Reflectivity (%) Summertime Daily Average and Maximum Air Temperatures for Roof System Reflectivity Simulations Conducted for City of Chicago Source: Dupuis , R. & Graham, M. (2005) “Study on Roof System Reflectivity and Near-Surface Air Temperatures in Chicago, IL.” Paper presented at “Cool Roofing … Cutting Through the Glare”, Atlanta Georgia.

  7. Cool Roofing…Cutting Through the Glare Cool Roofs & Surface Aging Roof Reflectance After Field Exposure Oak Ridge Laboratories Envelope Systems Research Apparatus (ESRA) 75% + Initial Reflectivity Test Membrane A Declines to… Test Membrane B 50% to 60% Reflectivity after 3 Years Reflectivity (%) Exposure (Months) Source: Miller, W.A., M. Cheng, S. Pfiffer and N. Byers. (2002). The Field Performance of High-Reflectance Single-Ply Membranes Exposed to Three Years of Weathering in Various U. S. Climates. Oak Ridge, TN: Oak Ridge National Laboratory.

  8. Cool Roofing…Cutting Through the Glare Cool Roof Alternatives • Ballasted Roofs • Increased Roof Insulation

  9. Cool Roof Alternatives: Ballasted Roofs Which Roof Saves The Most Energy? White Roof with 70% Reflectance Ballasted Roof with 17 lb. Stone Ballasted Roof with 10 lb. Stone Black Roof with 5% Reflectance Ballasted Roof with Concrete Pavers

  10. Cool Roof Alternatives: Ballasted Roofs Roof Membrane Surface Temperature: Clear Summer Day In East Tennessee (Oak Ridge National Laboratories) Exposed Black EPDM Membrane 180ºF Ballasted EPDM Under 10 lb. Stone 136ºF Exposed White TPO Membrane 122ºF Ballasted EPDM Under Concrete Pavers 120ºF Note: Area Under Curve Indicates Total Heat Absorbed Source: Gillenwater, D., Petrie, T., Miller W., & Desjarlais, A. (2005) “Are Ballasted Roof Systems Cool?” Paper presented at “Cool Roofing … Cutting Through the Glare”, Atlanta Georgia.

  11. Cool Roof Alternatives: Ballasted Roofs Overall Energy Savings: Equivalent to an aged reflective roof (50% reflectivity) Equivalent to a new reflective roof (70% reflectivity) Equivalent to any reflective roof (Up to 100% reflectivity) Roofing Alternative: Roofs with Light Stone Ballast (10 lb. / sq. ft.) Roofs with Heavy Stone Ballast (17-20 lb. / sq. ft.) Roofs with Concrete Pavers Source: Gillenwater, D., Petrie, T., Miller W., & Desjarlais, A. (2005) “Are Ballasted Roof Systems Cool?” Paper presented at “Cool Roofing … Cutting Through the Glare”, Atlanta Georgia.

  12. Cool Roof Alternatives: Increased Roof Insulation What is the R-Value for a Non-Reflective Roof to Provide Equivalent Energy Savings to a Reflective Roof with R-20 Insulation? White Roof with 55% Reflectance Black Roof with 5% Reflectance v. R-20 Insulation R-? Insulation Source: Hoff, J. L. (2005). “The Economics of Cool Roofing: A Local and Regional Approach.” Paper presented at “Cool Roofing … Cutting Through the Glare”, Atlanta Georgia.

  13. Cool Roof Alternatives: Increased Roof Insulation R-Value For A Non-Reflective Roof To Provide Equivalent Energy Savings to a Reflective Roof with R-20 Insulation Seattle Portland R-19 Portland Minneapolis Boise R-20 San Francisco Boston Detroit Cheyenne Milwaukee Pittsburgh Reno R-21 Chicago New York Cleveland Boulder SLC Baltimore Indianapolis Kansas City R-23 Richmond Louisville Las Vegas St. Louis Los Angeles Charlotte Nashville R-30 Little Rock R-26 Phoenix Atlanta Albuquerque R-33 Birmingham Jacksonville Ft. Worth Tampa New Orleans Houston Miami Source: Hoff, J. L. (2005). “The Economics of Cool Roofing: A Local and Regional Approach.” Paper presented at “Cool Roofing … Cutting Through the Glare”, Atlanta Georgia.

  14. Cool Roofing…Cutting Through the Glare Economic Issues • Scale: What does it mean to the individual building owner? • Location: What does it mean to a building owner in a particular location?

  15. The Economics of Cool Roofing Scale Effects Potential net annual energy savings from reflective roofs for an entire city New York: $16 Million Chicago: $10 Million Los Angeles: $35 Million Dallas: $20 Million Miami: $20 Million Source: Lawrence Berkeley National Laboratory Heat Island Group

  16. The Economics of Cool Roofing Scale Effects Potential net annual energy savings for a typical 20,000 square foot building New York $360 Chicago $20 Los Angeles $300 Dallas $520 Miami $760 Source: DOE Cool Roof Calculator

  17. The Economics of Cool Roofing Scale Effects Potential net annual energy savings per square foot of roof Chicago $0.001 New York $0.018 Los Angeles $0.015 Dallas $0.026 Miami $0.38 Source: DOE Cool Roof Calculator

  18. The Economics of Cool Roofing Regional Differences Everyone is aware that there are significant climate differences across the United States… U.S. Low* 141 (Miami) 69 (San Francisco) 1061 (Seattle) U.S. High* 7521 (Milwaukee) 4127 (Miami) 1839 (Phoenix) Variance 5234% 5881% 73% Climate Metric Heating Degree Days Cooling Degree Days Solar Load (BTU/ Sq. Ft. / Day) * For Standard Metropolitan Statistical Areas Source: DOE Cool Roof Calculator

  19. The Economics of Cool Roofing Regional Differences …but differences in energy costs are just as important U.S. Low* $0.0558 (Louisville) $0.0724 (Salt Lake City) U.S. High* $0.1236 (New York City) $1.2500 (Atlanta) Variance 122% 73% Energy Source Electricity ($ / KWH) Natural Gas ($ / Therm) * For Standard Metropolitan Statistical Areas Source: Energy Information Administration, June, 2004

  20. The Economics of Cool Roofing Building Comparison 5% Reflectance 80% Emittance Elec. Cooling (COP = 2.0) Gas Heat (70% Efficiency) 55% Reflectance 80% Emittance Elec. Cooling (COP = 2.0) Gas Heat (70% Efficiency) v. 20,000 Sq. Ft. 20,000 Sq. Ft. R-20 Insulation R-20 Insulation

  21. Annual Heating / Cooling Cost Savings: Reflective Roof versus Non-Reflective Roof (Dollars per 20,000 Sq. Ft. Roof Area / R-20 Insulation) (-$100) Seattle Portland (-$50) Portland Minneapolis $0 Boise $100 San Francisco Boston Detroit Cheyenne Milwaukee $200 Pittsburgh Reno (-$50) Chicago New York Cleveland Boulder SLC Baltimore $0 Indianapolis Kansas City $100 Richmond Louisville $200 Las Vegas St. Louis Los Angeles Charlotte Nashville Little Rock Ok. City $300 $300 Phoenix Atlanta Albuquerque $400 Birmingham $500 $400 Jacksonville Ft. Worth $500 Tampa New Orleans Houston Miami Source: Hoff, J. L. (2005). “The Economics of Cool Roofing: A Local and Regional Approach.” Paper presented at “Cool Roofing … Cutting Through the Glare”, Atlanta Georgia.

  22. Cool Roofing…Cutting Through the Glare Recommendations (For Dallas / Ft. Worth) • Cool roofs offer tangible benefits for individuals and the community: • Energy savings • Reduced urban heat island effect

  23. Cool Roofing…Cutting Through the Glare Recommendations (For Dallas / Ft. Worth) • … but there are several cool roofing alternatives to consider: • Reflective membranes • Reflective coatings • Ballasted membranes

  24. Cool Roofing…Cutting Through the Glare Recommendations (For Dallas / Ft. Worth) • … and several important issues must be recognized: • The total energy payback is fairly small • Less than $0.03 per sq. ft. annually • May be inadequate to justify a significant cost up-charge • Reflective membranes will age • Assume 50% to 55% as a reasonable long-term value • Energy payback may be inadequate to justify cleaning & maintenance • Roof insulation will lose less long-term energy value

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