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“Radiant Barrier Technology – A Must in Green Architecture”

“Radiant Barrier Technology – A Must in Green Architecture”. Mario A. Medina, Ph.D., P.E. Introduction. “ Preventing the sun's radiation from entering through the roof can make a significant contribution to comfort and reduction in cooling bills/needs. ”

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“Radiant Barrier Technology – A Must in Green Architecture”

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  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. Introduction • “Preventing the sun's radiation from entering through the roof can make a significant contribution to comfort and reduction in cooling bills/needs.” From: Sustainable Building Sourcebook Chapter: Energy  

  3. Definition 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. (Source: Florida Solar Energy Center)

  4. Radiant Barriers • Installation Configurations Pre-laminated Roof Sheathing

  5. Radiant Barriers • How are they installed?

  6. Radiant Barriers • How are they installed?

  7. Radiant Barriers • How they work: • Radiant barriers reduce radiated heat transfer rate by the combination of the low emittance/high reflectance properties of the foil.

  8. Radiant Barriers • Modes of Heat Transfer (Source: Btubusters)

  9. Radiant Barriers Heat transfer schematic Radiant Barrier Radiant Barrier

  10. Radiant Barriers • In the present study, the performance of radiant barriers was assessed via: • Experiments • Side by side monitoring of pre- and post-retrofit data. • Modeling • Mathematical representation of thermal sciences that describe the processes that take place. • Implemented using computer programming (e.g., FORTRAN). • Model/Experiment Validation

  11. Radiant Barriers • Experiments: Test Houses

  12. Radiant Barriers • Experiments: Sensors

  13. Radiant Barriers • Experiments: Monitoring Equipment

  14. Radiant Barriers • Experimental Results: Calibration (No RB Case) Ceiling Heat Flux Indoor Air Temperature < 3 % < 0.3 oF

  15. Radiant Barriers • Experimental Results: Calibration (RB Case) Ceiling Heat Flux Indoor Air Temperature < 3 % < 0.3 oF

  16. Radiant Barriers • Experimental Results: Effect of Radiant Barriers (~28% Daily Heat Flow Reduction) 37.5%

  17. Radiant Barriers • Experimental Results: Installation ComparisonsHorizontal Configuration vs. Truss Configuration? ~ 5 % Slight Advantage for the Horizontal Configuration

  18. Radiant Barriers • Experimental Results: Shingle Temperatures Horizontal Configuration Truss Configuration vs. No RB Case vs. No RB Case No difference in shingle temperature

  19. Radiant Barriers • Experimental Results: Effects of Daily Solar Radiation

  20. Radiant Barriers • Experimental Results: Effects of Attic Ventilation

  21. Radiant Barriers • Experimental Results: Effects of Attic Insulation Level 42% 34% 25%

  22. Radiant Barriers • Modeling: Based on Energy Balance Approach at Each Enclosing Surface

  23. Radiant Barriers • ModelingEnergy Balance (General) Energy Balance (Heat Transport Processes)Outdoor Energy BalanceIndoor Energy Balance 

  24. Radiant Barriers • Modeling: Solar Modeling

  25. Radiant Barriers • Verification of Model/Experiments (No RB Case)

  26. Radiant Barriers • Verification of Model/Experiments Horizontal Configuration Truss Configuration

  27. Radiant Barriers • Verification of Model/Experiments (Winter) No Radiant Barrier Configuration Horizontal Configuration 15 % Reduction in Heat Leaving Across the Attic

  28. Radiant Barriers • Verification of Model/Experiments No Radiant Barrier Configuration Horizontal Configuration

  29. Radiant Barriers • Computer Simulations: Yearly Performance Horizontal Configuration Truss Configuration 34 % Jun - Aug 32 % Jun - Aug

  30. Radiant Barriers • Computer Simulations: Yearly Performance

  31. Radiant Barriers • Computer Simulations: Attic Ventilation Pattern (Soffit/Soffit) Jun - Aug 31.6% 33.1% No RB Horizontal Truss

  32. Radiant Barriers • Computer Simulations: Attic Ventilation Pattern (Roof/Soffit) Jun - Aug 26.2% 31.4% No RB Truss Horizontal

  33. Radiant Barriers • Computer Simulations: Attic Ventilation Pattern (Soffit/Ridge) Jun - Aug 32.3% 28.2% No RB Truss Horizontal

  34. Radiant Barriers • Computer Simulations: Impact of Radiant Barrier on Cooling Demand as a Function of Insulation Degradation

  35. Radiant Barriers • Computer Simulations: Climate Influence

  36. Radiant Barriers • Computer Simulations: Climate Influence

  37. Radiant Barriers • Computer Simulations: Climate Influence

  38. Radiant Barriers • Computer Simulations: Climate Influence

  39. Radiant Barriers • Computer Simulations: Climate Influence

  40. Radiant Barriers • Computer Simulations: Climate Influence

  41. Radiant Barriers • Computer Simulations: Climate Influence

  42. Radiant Barriers • Parametric Analyses: Outdoor Air Temperature

  43. Radiant Barriers • Parametric Analyses: Mean Hourly Relative Humidity

  44. Radiant Barriers • Parametric Analyses: Mean Hourly Global (H) Radiation

  45. Radiant Barriers • Parametric Analyses: Latitude

  46. Radiant Barriers • Parametric Analyses: Altitude

  47. Radiant Barriers • Parametric Analyses: Roof Solar Absorptivity

  48. Radiant Barriers • Parametric Analyses: Radiant Barrier Emissivity

  49. Radiant Barriers • Parametric Analyses: Attic Airflow Rate

  50. Radiant Barriers • Parametric Analyses: Roof Slope

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