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Radiant Barrier Study

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Radiant Barrier Study

  1. 1. “ Radiant Barrier Technology – A Must in Green Architecture” Mario A. Medina, Ph.D., P.E. Civil, Environmental, and Architectural Engineering The University of Kansas
  2. 2. Introduction <ul><li>“ Preventing the sun's radiation from entering through the roof can make a significant contribution to comfort and reduction in cooling bills/needs. ” </li></ul><ul><li>From: Sustainable Building Sourcebook </li></ul><ul><li>Chapter: Energy   </li></ul>
  3. 3. Definition <ul><li>A radiant barrier consists of a layer of metallic foil, with low emittance, that significantly reduces the transfer of heat energy radiated from “hotter” surfaces to “colder” surfaces (e.g., the deck of an attic to the attic floor). Among the benefits of installing radiant barriers are energy savings, $ savings, and comfort. </li></ul>(Source: Florida Solar Energy Center)
  4. 4. Radiant Barriers <ul><li>Installation Configurations </li></ul>Pre-laminated Roof Sheathing
  5. 5. Radiant Barriers <ul><li>How are they installed? </li></ul>
  6. 6. Radiant Barriers <ul><li>How are they installed? </li></ul>
  7. 7. Radiant Barriers <ul><li>How they work: </li></ul><ul><ul><li>Radiant barriers reduce radiated heat transfer rate by the combination of the low emittance/high reflectance properties of the foil. </li></ul></ul>
  8. 8. Radiant Barriers <ul><li>Modes of Heat Transfer </li></ul><ul><li>(Source: Btubusters) </li></ul>
  9. 9. Radiant Barriers <ul><li>Heat transfer schematic </li></ul>Radiant Barrier Radiant Barrier
  10. 10. Radiant Barriers <ul><li>In the present study, the performance of radiant barriers was assessed via: </li></ul><ul><ul><li>Experiments </li></ul></ul><ul><ul><ul><li>Side by side monitoring of pre- and post-retrofit data. </li></ul></ul></ul><ul><ul><li>Modeling </li></ul></ul><ul><ul><ul><li>Mathematical representation of thermal sciences that describe the processes that take place. </li></ul></ul></ul><ul><ul><ul><li>Implemented using computer programming (e.g., FORTRAN). </li></ul></ul></ul><ul><ul><li>Model/Experiment Validation </li></ul></ul>
  11. 11. Radiant Barriers <ul><li>Experiments: Test Houses </li></ul>
  12. 12. Radiant Barriers <ul><li>Experiments: Sensors </li></ul>
  13. 13. Radiant Barriers <ul><li>Experiments: Monitoring Equipment </li></ul>
  14. 14. Radiant Barriers <ul><li>Experimental Results: Calibration (No RB Case ) </li></ul><ul><ul><li>Ceiling Heat Flux Indoor Air Temperature </li></ul></ul>< 3 % < 0.3 o F
  15. 15. Radiant Barriers <ul><li>Experimental Results: Calibration (RB Case) </li></ul><ul><ul><li>Ceiling Heat Flux Indoor Air Temperature </li></ul></ul>< 3 % < 0.3 o F
  16. 16. Radiant Barriers <ul><li>Experimental Results: Effect of Radiant Barriers (~28% Daily Heat Flow Reduction) </li></ul>37.5%
  17. 17. Radiant Barriers <ul><li>Experimental Results: Installation Comparisons Horizontal Configuration vs. Truss Configuration? </li></ul>Slight Advantage for the Horizontal Configuration ~ 5 %
  18. 18. Radiant Barriers <ul><li>Experimental Results: Shingle Temperatures </li></ul><ul><li>Horizontal Configuration Truss Configuration </li></ul><ul><li> vs. No RB Case vs. No RB Case </li></ul>No difference in shingle temperature
  19. 19. Radiant Barriers <ul><li>Experimental Results: Effects of Daily Solar Radiation </li></ul>
  20. 20. Radiant Barriers <ul><li>Experimental Results: Effects of Attic Ventilation </li></ul>
  21. 21. Radiant Barriers <ul><li>Experimental Results: Effects of Attic Insulation Level </li></ul>42% 34% 25%
  22. 22. Radiant Barriers <ul><li>Modeling: Based on Energy Balance Approach at Each Enclosing Surface </li></ul>
  23. 23. Radiant Barriers <ul><li>Modeling Energy Balance (General) </li></ul><ul><li>Energy Balance (Heat Transport Processes)  Outdoor Energy Balance Indoor Energy Balance  </li></ul>
  24. 24. Radiant Barriers <ul><li>Modeling: Solar Modeling </li></ul>
  25. 25. Radiant Barriers <ul><li>Verification of Model/Experiments (No RB Case) </li></ul>
  26. 26. Radiant Barriers <ul><li>Verification of Model/Experiments </li></ul><ul><li>Horizontal Configuration Truss Configuration </li></ul>
  27. 27. Radiant Barriers <ul><li>Verification of Model/Experiments (Winter) </li></ul><ul><li>No Radiant Barrier Configuration Horizontal Configuration </li></ul>15 % Reduction in Heat Leaving Across the Attic
  28. 28. Radiant Barriers <ul><li>Verification of Model/Experiments </li></ul><ul><li>No Radiant Barrier Configuration Horizontal Configuration </li></ul>
  29. 29. Radiant Barriers <ul><li>Computer Simulations: Yearly Performance </li></ul><ul><li>Horizontal Configuration Truss Configuration </li></ul>34 % Jun - Aug 32 % Jun - Aug
  30. 30. Radiant Barriers <ul><li>Computer Simulations: Yearly Performance </li></ul>
  31. 31. Radiant Barriers <ul><li>Computer Simulations: Attic Ventilation Pattern (Soffit/Soffit) </li></ul>Jun - Aug 33.1% 31.6% Horizontal Truss No RB
  32. 32. Radiant Barriers <ul><li>Computer Simulations: Attic Ventilation Pattern (Roof/Soffit) </li></ul>Jun - Aug 31.4% 26.2% Horizontal Truss No RB
  33. 33. Radiant Barriers <ul><li>Computer Simulations: Attic Ventilation Pattern (Soffit/Ridge) </li></ul>Jun - Aug 32.3% 28.2% Horizontal Truss No RB
  34. 34. Radiant Barriers <ul><li>Computer Simulations: Impact of Radiant Barrier on Cooling Demand as a Function of Insulation Degradation </li></ul>
  35. 35. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>
  36. 36. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>Climate Summer Monthly Dry Bulb Air Temperature o C ( o F) Summer Monthly Relative Humidity (%) Summer Monthly Wind Speed km/h (mi/h) Area Covered km 2 (mi 2 ) Percent Area Covered (%) Humid Subtropical 29 (84) 68 13.7 (8.5) 1,939,636 (750,430) 24.03 Humid Continental Warm Summer 25 (77) 70 14.1 (8.8) 1,655,112 (640,350) 20.50 Desert 28 (83) 47 13.0 (8.1) 1,223,467 (473,350) 15.16 Humid Continental Cool Summer 21 (70) 67 14.0 (8.7) 905,291 (350,250) 11.21 Steppe 17 (62) 43 12.7 (7.9) 739,043 (285,930) 9.15 Marine West Coast 15 (59) 80 13.3 (8.3) 560,259 (216,760) 6.94 Mediterranean 17 (63) 74 16.1 (10.0) 508,837 (196,865) 6.30 Western High Areas 20 (68) 50 13.7 (8.5) 481,581 (186,320) 5.97 Tropical Savanna 28 (83) 77 12.9 (8.0) 59,484 (23,014) 0.74 TOTAL 8,072,711 (3,123,269) 100.00
  37. 37. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>
  38. 38. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>
  39. 39. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>
  40. 40. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>
  41. 41. Radiant Barriers <ul><li>Computer Simulations: Climate Influence </li></ul>Climate Sample Station Sample Summer Integrated Percent Reduction (SIPR) (%) Average Peak-Hour Percent Reduction (PHPR) (%) Humid Subtropical San Antonio, TX New York- NY Atlanta, GA 34.3 32.5 38.5 35.1 31 Humid Continental Warm Summer Topeka, KS Indianapolis, IN 30.0 30.1 30.5 46 Desert Las Vegas, NV Tucson, AZ 19.2 23.0 21.1 23 Humid Continental Cool Summer Minneapolis, MN Detroit, Michigan 25.7 24.3 25.0 54 Steppe Pocatello, ID Helena, MT 16.0 13.7 14.9 36 Marine West Coast Astoria, OR 9.6 9.6 ~100 Mediterranean San Francisco, CA 2.3 2.3 97 Western High Areas Boulder, CO 19.7 19.7 44 Tropical Savanna Miami, FL 36.8 36.8 42
  42. 42. Radiant Barriers <ul><li>Parametric Analyses: Outdoor Air Temperature </li></ul>
  43. 43. Radiant Barriers <ul><li>Parametric Analyses: Mean Hourly Relative Humidity </li></ul>
  44. 44. Radiant Barriers <ul><li>Parametric Analyses: Mean Hourly Global (H) Radiation </li></ul>
  45. 45. Radiant Barriers <ul><li>Parametric Analyses: Latitude </li></ul>
  46. 46. Radiant Barriers <ul><li>Parametric Analyses: Altitude </li></ul>
  47. 47. Radiant Barriers <ul><li>Parametric Analyses: Roof Solar Absorptivity </li></ul>
  48. 48. Radiant Barriers <ul><li>Parametric Analyses: Radiant Barrier Emissivity </li></ul>
  49. 49. Radiant Barriers <ul><li>Parametric Analyses: Attic Airflow Rate </li></ul>
  50. 50. Radiant Barriers <ul><li>Parametric Analyses: Roof Slope </li></ul>
  51. 51. Radiant Barriers <ul><li>In Conclusion…. </li></ul>
  52. 52. <ul><ul><li>THANK YOU </li></ul></ul>

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