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Dr. James L. Hoff, DBA PowerPoint Presentation
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Dr. James L. Hoff, DBA

Dr. James L. Hoff, DBA

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Dr. James L. Hoff, DBA

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  1. INTRODUCTION TO LOW-SLOPE ROOFING Dr. James L. Hoff, DBA

  2. Commercial Roofing • Historical Perspective • Modern Roofing Materials • Roofing • New Roofing Trends

  3. Historical BackgroundPre-1900: Before the Modern Age • Roofing materials selected for durabilityand appearance • Slate • Tile • Metal • Roofing systems designed to shed water • Gables • Hips • Valleys • Crowns • Saddles • Gutters • Downspouts

  4. Historical Background1920s : The Bauhaus • Lightweight Framing Systems • Roof weight becomes a consideration • Rectangular, Low-Rise Profiles • Roof plane becomes virtually level • Facades and Parapets • Roof becomes an isolated sump As a result, roofing materials were selected on the basis of durability and weight, while roof systems were designed to resist water.

  5. Historical BackgroundToday : The “Big Box” What started as architectural theory is now economic fact “Steeply sloped roofs on the large, sprawling buildings that dominate today’s construction would dramatically cut the costs of re-roofing, repair and litigation. but they would raise construction costs by a far greater amount …the costs of steeply sloped roofs over the vast acreages covered by modern buildings are simply too high a price to pay to avoid the problems posed by low-slope roof systems.” (C. W. Griffith & R. Fricklas, Manual of Low-Slope Roofing Systems, 1996)

  6. Historical Background1840s – 1970s: Built-Up Roofing

  7. Historical Background1840s – 1970s: Built-Up Roofing • Originally employed to waterproof ships • Redundant layers of bitumen & felts • Bitumen serves as adhesive and waterproofing • Felts stabilize and strengthen the bitumen • Frequently surfaced with aggregate • Traditional “tar & gravel” roof

  8. Historical Background1840s – 1970s: Built-Up Roofing • Dominated commercial roofing for over a century • Provided a satisfactory barrier to water entry • Success attributed to redundancy of design and well-understood application standards

  9. Historical Background1970s: The Perfect Storm • Health concerns over asbestos • Asbestos felts replaced by organic (paper) felts • Lower strength • Higher moisture absorption • OPEC oil embargo • Cost of asphalt increased dramatically • Quality of asphalt decreased • Increasing energy efficiency • Higher “R” insulations installed under built-up membranes • Splitting due to “thermal shock” increased

  10. Historical Background1980s: New Answers – And Plenty of Them • Tire manufacturers introduce rubber roofing Neoprene, Butyl, EPDM • Textile manufacturers introduce thermoplastic roofing PVC, CPE, CSPE, E-P, TPO, HDPE • Asphalt manufacturers introduce polymer-modified roofing APP, SBS, SEBS, E-P • Chemical manufacturers introduce synthetic coatings Acrylics, Polyurethanes “According to industry estimates, over 100 new manufacturers of roofing products emerged during the ‘70s and early ‘80s, each offering the ‘miracle’ answer for roofing performance.” (J.L. Hoff, “The Commercial Roofing Industry: New Directions in Construction Quality”, 2003)

  11. Historical Background1990s: Consolidation • Rubber roofing consolidates around EPDM • Thermoplastic roofing consolidates around PVC and TPO • Polymer modification (APP & SBS) integrates into traditional asphalt roofing • Roof coatings relegated primarily to maintenance applications

  12. U.S. Low-Slope Commercial Roofing Market Key Market Segments (Millions of Square Feet 2003) Single-Ply Asphalt Built-Up Roofing (BUR) Rubber Roofing (EPDM) 17% 30% 30% 23% Thermoplastic (PVC & TPO) Modified Asphalt (APP & SBS)

  13. Roofing System OverviewSingle-Ply • THERMOSET • EPDM • THERMOPLASTIC • PVC • TPO

  14. Roofing System OverviewEPDM • Large panel sizes for fast coverage • Outstanding resistance to weathering • High elongation to accommodate building movement

  15. Simple, economical design provides proven performance • Stone ballast provides Class A Fire Rating • Compatible with most insulations • Large panels provide efficient coverage of large roof areas Roofing System OverviewEPDM: Ballasted System Stone Ballast or Pavers Membrane Insulation Deck

  16. Roofing System OverviewEPDM: Ballasted System

  17. Roofing System OverviewEPDM: Ballasted System

  18. Adhesive Adhesive Roofing System OverviewEPDM: Adhered System Membrane Insulation plates & fasteners Deck Insulation • Design Flexibility - Adapts easily to unusual roof profiles • Excellent for high wind conditions • Time-proven application method provides high dependability

  19. Roofing System OverviewEPDM: Adhered System

  20. Roofing System OverviewEPDM: Adhered System

  21. Roofing System OverviewEPDM: Mechanically Attached Metal Or Polymer Batten Membrane Embedded In Field Seam Deck Seaming Tape Insulation • Light weight - adapts to most roof decks • Reduced labor input

  22. Roofing System OverviewEPDM: Mechanically Attached

  23. Roofing System OverviewEPDM: Mechanically Attached

  24. Roofing System OverviewThermoplastic • Heat-reflective white surface • Fast, simple welded panel seams • Available in variety of colors

  25. Roofing System OverviewThermoplastic Installation

  26. Roofing System OverviewThermoplasticInstallation

  27. Roofing System OverviewAsphalt • Built-Up Roofing • BUR • Modified Bitumen • APP • SBS

  28. Roofing System OverviewBuilt-Up Roofing (BUR) Gravel Surfacing Cover Board Insulation Ply Felts Set In Asphalt

  29. Roofing System OverviewBuilt-Up Roofing (BUR) Roofing Felts in Hot Asphalt

  30. Roofing System OverviewBuilt-Up Roofing (BUR) Gravel-Surfaced BUR

  31. Roofing System OverviewModified Bitumen

  32. Roofing System OverviewModified Bitumen Cap Sheet Cover Board Insulation Base Sheet

  33. Roofing System OverviewModified Bitumen Asphalt Modifiers • SBS • Styrene-Butadiene-Styrene • Thermoset (Rubber) Polymer • Adds Flexibility & Memory • Excellent Low Temp. Flexibility • Requires uV Resistant Surfacing • APP • Atactic Polypropylene • Thermoplastic Polymer • Adds Flexibility • Excellent High Temp. Strength • Excellent uV Resistance

  34. Roofing System OverviewModified Bitumen Hot Mopped Torch Applied Cold Applied

  35. Roofing System OverviewModified Bitumen

  36. Roofing System PerformanceHow Long Do Roofs Last? System Type Single-Ply Built-Up Roofing Modified Bitumen Average Service Life 16.8 – 18.4 Years 13.6 – 18.1 Years 17.6 – 18.2 Years “A documented historical performance of roofing assemblies in the United States: 1975–1996”. K. G. Schneider & A. S. Keenan.. Proceedings of the Fourth International Symposium on Roofing Technology (pp. 132-137). Rosemont, IL: National Roofing Contractors Association, 1997. “…Life span is defined as the time period from the initial roofing membrane installation through recover/re-roof. Based on the results of the statistical model, the current average low slope roofing life span is estimated to be 17.45 years” “Comprehensive Nonresidential Building Analysis to Estimate the Current Reality of Roofing Longevity”, Ducker Research, 2003.

  37. Roofing System OverviewPerformance Features • Ultraviolet Aging • Roof Traffic • Chemical Exposure • Building Movement • Reflectivity • Color Options • High Production • Work Area Limitations • Relative Cost EPDM +++ + +++ +++ ++ 1.0 - 1.2 PVC/TPO + + + (PVC) + ++ ++ ++ ++ 1.1 - 1.3 BUR + +++ ++ 1.2 - 1.4 Mod Bit + ++ + +++ + +++ 1.1 - 1.3

  38. Roofing System OverviewRoof Insulation One Component Three Functions

  39. Roofing InsulationThermal Barrier Typical “R” Value per Inch Thickness

  40. Roofing Insulation:Working Platform

  41. Roofing Insulation:Drainage Structure

  42. Roofing System OverviewDrainage Issues Typical 2-Way Structural Slope Slope

  43. Roofing System OverviewDrainage Issues Interior Drain (Typ.) Typical 2-Way Structural Slope

  44. Roofing System OverviewDrainage Solution 4-Way Slope using Tapered Insulation

  45. Roofing System OverviewNew Roofing Trends & Concepts • Cool Roofs • Green / Garden Roofs • Solar Roofs • Roof Recycling

  46. Cool Roofs:Saving Energy & Reducing Urban Heat Islands Cool Metal Roofs Cool Membrane Roofs Ice Mountain Brea, CA Lindberg Terminal St. Louis , MO • Peak Cooling Loads Reduced • Ambient Air Temperatures Reduced

  47. (-$100) Seattle Portland (-$50) Portland Minneapolis $0 Boise (-$50) $100 San Francisco Boston Detroit Cheyenne Milwaukee $200 Pittsburgh Reno Chicago New York Cleveland $0 Boulder SLC Baltimore Indianapolis $100 Kansas City Richmond Louisville Las Vegas $200 St. Louis Los Angeles Charlotte Nashville Little Rock $300 Ok. City $300 Phoenix Atlanta Albuquerque $400 $400 Birmingham Jacksonville $500 Ft. Worth $500 Tampa Houston New Orleans Miami Cool Roofs:Current Issues & Concerns Are Cool Roofs Right For All Climates? How Do You Maintain Surface Reflectivity? Minute Maid Stadium Houston, TX Annual Heating / Cooling Cost Savings: Reflective Roof versus Non-Reflective Roof (Dollars per 20,000 Sq. Ft. Roof Area / R-20 Insulation)

  48. New Cool Roof Alternatives:Stone & Paver Ballasted Systems Envelop Systems Research Apparatus Oak Ridge National Laboratories

  49. New Cool Roof Alternatives:Stone & Paver Ballasted Systems Black Roof Standard Ballast White Roof Heavy Ballast Concrete Pavers Comparative Surface Temperature & Heat Transfer Ballasted roofs can provide the same peak energy savings and reduced air temperatures as “cool” roofs …and their performance doesn’t degrade over time!

  50. Garden / Green Roofs:Saving Energy & Reducing Pollution Chicago City Hall Chicago, IL US Environmental Protection Agency Denver, CO