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

Commercial Roofing Historical Perspective Modern Roofing Materials Roofing New Roofing Trends

Historical Background Pre-1900: Before the Modern Age Roofing materials selected for durability and appearance Slate Tile Metal Roofing systems designed to shed water Gables Hips Valleys Crowns Saddles Gutters Downspouts

Historical Background 1920s : 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.

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) Historical Background Today : The “Big Box”

Historical Background 1840s – 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 Historical Background 1840s – 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

Historical Background 1970s: 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

Historical Background 1980s: New Answers – And Plenty of Them “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) 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

Historical Background 1990s: 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

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

Roofing System Overview Single-Ply THERMOSET EPDM THERMOPLASTIC PVC TPO

Roofing System Overview EPDM +Large panel sizes for fast coverage +Outstanding resistance to weathering +High elongation to accommodate building movement

Roofing System Overview EPDM: Ballasted System 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 Insulation Deck Stone Ballast or Pavers Membrane

Roofing System Overview EPDM: Ballasted System

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

Roofing System Overview EPDM: Adhered System

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

Roofing System Overview EPDM: Mechanically Attached

Roofing System Overview Thermoplastic +Heat-reflective white surface +Fast, simple welded panel seams +Available in variety of colors

Roofing System Overview Thermoplastic Installation

Roofing System Overview Asphalt Built-Up Roofing BUR Modified Bitumen APP SBS

Roofing System Overview Built-Up Roofing (BUR) Insulation Cover Board Ply Felts Set In Asphalt Gravel Surfacing

Roofing System Overview Built-Up Roofing (BUR) Roofing Felts in Hot Asphalt

Roofing System Overview Built-Up Roofing (BUR) Gravel-Surfaced BUR

Roofing System Overview Modified Bitumen

Insulation Cover Board Base Sheet Cap Sheet Roofing System Overview Modified Bitumen

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

Hot Mopped Cold Applied Torch Applied Roofing System Overview Modified Bitumen

Roofing System Performance How 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 ). Rosemont, IL: National Roofing Contractors Association, “…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 years” “Comprehensive Nonresidential Building Analysis to Estimate the Current Reality of Roofing Longevity”, Ducker Research, 2003.

Ultraviolet Aging Roof Traffic Chemical Exposure Building Movement Reflectivity Color Options High Production Work Area Limitations Relative Cost EPDM PVC/TPO + + (PVC) BUR Mod Bit Roofing System Overview Performance Features

Roofing System Overview Roof Insulation One Component Three Functions

Roofing Insulation Thermal Barrier Typical “R” Value per Inch Thickness

Roofing Insulation: Working Platform

Roofing Insulation: Drainage Structure

Roofing System Overview Drainage Issues Slope Typical 2-Way Structural Slope

Interior Drain (Typ.) Typical 2-Way Structural Slope Roofing System Overview Drainage Issues

4-Way Slope using Tapered Insulation Roofing System Overview Drainage Solution

Roofing System Overview New Roofing Trends & Concepts Cool Roofs Green / Garden Roofs Solar Roofs Roof Recycling

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

How Do You Maintain Surface Reflectivity? Are Cool Roofs Right For All Climates? 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) Cool Roofs: Current Issues & Concerns

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

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

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

 Underlying roof system must accommodate increased maintenance traffic  Underlying roof system must be designed to meet or exceed to expected garden service life  Leak detection is difficult  Roof repair and maintenance may be difficult if/when needed  Ambient air temperature reduced  Storm water runoff mitigated  Wide variety of hardy plants available  Require as little as 2 or 3 inches of planting medium  Can be combined with “cool” ballasted roofs to minimize initial costs  Tray systems available to minimize maintenance needs Benefits:Issues: Garden / Green Roofs: Benefits & Issues

Solar Roofs: Clean Energy Production Target Store Stockton, CA Shiseido Windsor, NJ

Benefits:Issues: Solar Roofs: Benefits & Issues  Economics not yet at “grid parity”  Underlying roof system must accommodate increased maintenance traffic  Underlying roof system must be designed to meet or exceed to expected solar system service life  Leak detection may be difficult  Roof repair and maintenance may be difficult if/when needed  Clean energy generated  Peak energy demands reduced

Roof Recycling: Reducing Landfill Waste Cookson Elementary School Troy, Ohio 1 Windrow & Sweep 2 Cut & Stack 3 Chop 4 Grind Sieve & Package 5 Recycle 6

Benefits:Issues: Roof Recycling: Benefits & Issues  Economics do not currently support  Only available in a regional pilot program for selected products  Logistics (removal, storage, transportation) are very difficult  Recyclers must have an assured supply before end markets can be fully developed  Currently limited to “down- cycling” in other products  Landfill waste reduced  Overall environmental impact reduced

 Roofing materials will be thinner and lighter – all bringing new challenges for durability  Roofs will be installed with eventual removal in mind  Maintenance programs will become more sophisticated in order to extend service life  The primary concern of the building owner will continue to be durability Commercial Roofing: Looking to the Future