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Dr. James L. Hoff, DBA

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INTRODUCTION TO LOW-SLOPE ROOFING Dr. James L. Hoff, DBA Historical Background Pre-1900: Before the Modern Age Roofing materials selected for durability and ... – PowerPoint PPT presentation

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Title: Dr. James L. Hoff, DBA


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 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

4
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.
5
Historical Background Today The Big Box
  • What started as architectural theory is now
    economic fact

Steeply sloped roofs on the large, sprawling
buildings that dominate todays 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 Background 1840s 1970s Built-Up
Roofing
7
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

8
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

9
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

10
Historical Background 1980s 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 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

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 Overview Single-Ply
  • THERMOSET
  • EPDM
  • THERMOPLASTIC
  • PVC
  • TPO

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

15
Roofing System Overview EPDM Ballasted System
Stone Ballast or Pavers
Membrane
Insulation

Deck
16
Roofing System Overview EPDM Ballasted System
17
Roofing System Overview EPDM Ballasted System
18
Roofing System Overview EPDM 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 Overview EPDM Adhered System
20
Roofing System Overview EPDM Adhered System
21
Roofing System Overview EPDM 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 Overview EPDM Mechanically
Attached
23
Roofing System Overview EPDM Mechanically
Attached
24
Roofing System Overview Thermoplastic
  • Heat-reflective white surface
  • Fast, simple welded panel seams
  • Available in variety of colors

25
Roofing System Overview Thermoplastic Installation
26
Roofing System Overview Thermoplastic Installation
27
Roofing System Overview Asphalt
  • Built-Up Roofing
  • BUR
  • Modified Bitumen
  • APP
  • SBS

28
Roofing System Overview Built-Up Roofing (BUR)
Gravel Surfacing
Cover Board
Insulation
Ply Felts Set In Asphalt
29
Roofing System Overview Built-Up Roofing (BUR)
Roofing Felts in Hot Asphalt
30
Roofing System Overview Built-Up Roofing (BUR)
Gravel-Surfaced BUR
31
Roofing System Overview Modified Bitumen
32
Roofing System Overview Modified Bitumen
Cap Sheet
Cover Board
Insulation
Base Sheet
33
Roofing System Overview Modified 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 Overview Modified Bitumen
Hot Mopped
Torch Applied
Cold Applied
35
Roofing System Overview Modified Bitumen
36
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 19751996. 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 Overview Performance 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 Overview Roof Insulation
One Component Three Functions
39
Roofing Insulation Thermal Barrier
Typical R Value per Inch Thickness
40
Roofing Insulation Working Platform
41
Roofing Insulation Drainage Structure
42
Roofing System Overview Drainage Issues
Typical 2-Way Structural Slope
Slope
43
Roofing System Overview Drainage Issues
Interior Drain (Typ.)
Typical 2-Way Structural Slope
44
Roofing System Overview Drainage Solution
4-Way Slope using Tapered Insulation
45
Roofing System Overview New Roofing Trends
Concepts
  • Cool Roofs
  • Green / Garden Roofs
  • Solar Roofs
  • Roof Recycling

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

47
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 doesnt degrade over
time!
50
Garden / Green Roofs Saving Energy Reducing
Pollution
Chicago City Hall Chicago, IL
US Environmental Protection Agency Denver, CO
51
Garden / Green Roofs Benefits Issues
Benefits
Issues
  • 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

52
Solar Roofs Clean Energy Production
Shiseido Windsor, NJ
Target Store Stockton, CA
53
Solar Roofs Benefits Issues
Benefits
Issues
  • Clean energy generated
  • Peak energy demands reduced
  • 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

54
Roof Recycling Reducing Landfill Waste
Cookson Elementary School Troy, Ohio
1
2
Windrow Sweep
Cut Stack
4
5
Sieve Package
Grind
55
Roof Recycling Benefits Issues
Benefits
Issues
  • Landfill waste reduced
  • Overall environmental impact reduced
  • 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

56
Commercial Roofing Looking to the Future
  • 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
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