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Historical Background Pre-1900: High Slopes / Low Spans

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Title: Historical Background Pre-1900: High Slopes / Low Spans


1
INTRODUCTION TO COMMERCIAL ROOFING
James L. Hoff, DBA
2
Commercial Roofing
  • Historical Perspective
  • Modern Roofing Materials
  • Membranes
  • Insulations
  • New Roofing Trends

3
Introduction to Commercial Roofing
A Brief History of Commercial Roofing
4
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

5
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.
6
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)
7
Historical Background 1840s 1970s Built-Up
Roofing
8
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

9
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

10
Historical Background 1970s The Perfect Storm
  • Asbestos health concerns
  • Traditional roofing felts relied on asbestos
    fibers for strength
  • Asbestos fibers replaced by lower strength
    organic (paper) fibers
  • OPEC oil embargo
  • Quality of roofing asphalt decreased as more
    gasoline was extracted from every barrel of oil
  • Roofing asphalt became more brittle, less plastic

11
Historical Background 1970s The Perfect Storm
  • The response Roof insulation increased to save
    energy
  • R value doubled or tripled
  • Roof surface isolated from building interior
  • Roof surface daily temperature swings up to 150ºF
  • The result Premature roof aging failure
  • Non-asbestos felts lacked strength and moisture
    resistance
  • Asphalt became brittle

12
Historical Background 1970s New Answers And
Plenty of Them
  • Tire manufacturers introduce Rubber Roofing
  • Neoprene, Butyl, EPDM
  • Textile manufacturers introduce Thermoplastic
    Roofing
  • PVC, PE, CPE, CSPE, E-P, TPO
  • Asphalt manufacturers introduce Polymer Modifiers
  • APP, SBS, SEBS

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)
13
Historical Background 1980s A Steep Learning
Curve
  • Rubber roofing
  • Leaks at adhesive seams
  • Thermoplastic roofing
  • Membrane cracking
  • Modified bitumen roofing
  • General workmanship issues

14
Historical Background 1980s The Lesson for the
Roofing Industry
"As an industry, we have spent far too much time
and far too many dollars fixing past problems
related to durability not to become unflinching
advocates for the utmost importance of
durability James L. Hoff. Advancing
Sustainable Roofing LEED and the Commercial
Roofing Industry." Proceedings of the 20th
International Convention of the Roof Consultants
Institute, Miami Beach, Florida, March, 2004.
15
Historical Background 1990s Consolidation /
Standardization
  • Rubber roofing consolidates around EPDM
  • New seaming technologies dramatically reduce
    leaks
  • Thermoplastic roofing consolidates around PVC
    TPO
  • Improved formulations offer long-term stability
  • Polymer modification (APP SBS) integrates into
    traditional asphalt roofing
  • Hybrid asphalt roofs use a combination of
    traditional BUR with modified flashings and cap
    sheets

16
Introduction to Commercial Roofing
Modern Roofing Materials
17
U.S. Low-Slope Commercial Roofing Market Key
Membrane 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)
Source TEGNOS Research Estimate
18
Modern Roofing Membranes Single-Ply
  • THERMOSET
  • EPDM
  • THERMOPLASTIC
  • PVC
  • TPO

19
Modern Roofing Membranes EPDM
  • Large panel sizes for fast coverage
  • Outstanding resistance to weathering
  • High elongation to accommodate building movement

20
Modern Roofing Membranes EPDM Ballasted System
Stone Ballast or Pavers
Membrane
Insulation

Deck
21
Modern Roofing Membranes EPDM Ballasted System
22
Modern Roofing Membranes EPDM Ballasted System
23
Modern Roofing Membranes 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

24
Modern Roofing Membranes EPDM Adhered System
25
Modern Roofing Membranes EPDM Adhered System
26
Modern Roofing Membranes 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

27
Modern Roofing Membranes EPDM Mechanically
Attached
28
Modern Roofing Membranes EPDM Mechanically
Attached
29
Modern Roofing Membranes Thermoplastic
  • Heat-reflective white surface
  • Fast, simple welded panel seams
  • Available in variety of colors

30
Modern Roofing Membranes Thermoplastic
Installation
31
Modern Roofing Membranes Thermoplastic
Installation
Ice Mountain Bottling Stanwood, MI
32
Modern Roofing Membranes Asphalt
  • Built-Up Roofing
  • BUR
  • Modified Bitumen
  • APP
  • SBS

33
Modern Roofing Membranes Built-Up Roofing (BUR)
Gravel Surfacing
Cover Board
Insulation
Ply Felts Set In Asphalt
34
Modern Roofing Membranes Built-Up Roofing (BUR)
Roofing Felts in Hot Asphalt
35
Modern Roofing Membranes Built-Up Roofing (BUR)
Gravel-Surfaced BUR
36
Modern Roofing Membranes Modified Bitumen
37
Modern Roofing Membranes Modified Bitumen
Cap Sheet
Cover Board
Insulation
Base Sheet
38
Modern Roofing Membranes 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

39
Modern Roofing Membranes Modified Bitumen
Hot Mopped
Torch Applied
Cold Applied
40
Modern Roofing Membranes Modified Bitumen
41
Modern Roofing Membranes Modified Bitumen
Miami Beach Convention Center Miami Beach, FL
Swenson Skills Center Philadelphia, PA
42
Modern Roofing Membranes How Long Do They Last?
Membrane 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.
43
Modern Roofing Membranes 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
44
Modern Roofing Materials Roof Insulation
One Component Three Functions
45
Roof Insulation Thermal Barrier
Typical R Value per Inch Thickness
46
Roof Insulation Working Platform
47
Roof Insulation Drainage Structure
48
Roof Insulation Drainage Issues
Typical 2-Way Structural Slope
Slope
49
Roof Insulation Drainage Issues
Interior Drain (Typ.)
Typical 2-Way Structural Slope
50
Roof Insulation Drainage Solution
4-Way Slope using Tapered Insulation
Detailed Tapered Roof Insulation Plan
51
Introduction to Commercial Roofing
New Roofing Trends
  • Cool Roofs
  • Vegetated Roofs
  • Solar Roofs
  • Green Materials

52
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

53
Cool Roofs The Urban Heat Island Effect
Temperature Profile of Atlanta 1972 v. 1993
Source CNN.Com
Source LBL Heat Island Group
54
Cool Roofs Saving Energy Reducing Urban Heat
Islands
Potential net energy savings from changing roof
reflectivity. Savings are measured in dollars.
Note that the net savings are the savings of
cooling energy use less the penalties of heating
energy use. (Source LBL Heat Island Group)
55
Cool Roofs Current Issues Concerns
How Do You Maintain Surface Reflectivity?
Minute Maid Stadium Houston, TX
56
Cool Roofs Current Issues Concerns
Are Cool Roofs Right For All Climates?
(-100)
(-50)
0
(-50)
100
Detroit
200
0
100
200
300
Ok. City
300
400
400
Jacksonville
500
500
Annual Heating / Cooling Cost Savings Reflective
Roof versus Non-Reflective Roof (Dollars per
20,000 Sq. Ft. Roof Area / R-20 Insulation)
57
New Cool Roof Alternative Stone Paver
Ballasted Systems
Envelop Systems Research Apparatus Oak Ridge
National Laboratories
58
New Cool Roof Alternative 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!
59
Vegetated Roofs Saving Energy Reducing
Pollution
Chicago City Hall Chicago, IL
US Environmental Protection Agency Denver, CO
60
Vegetated Roofs Reducing Storm Water Runoff
Both Cumulative
And Hourly
Source Penn State University Cool Roofing Program
61
Vegetated Roofs Intensive Green Roofs
Heavy Weight
Very Heavy Weight
Shrubs Trees Soil
Plants Shrubs Soil
12 36
36
Root Barrier / Drainage Mat Insulation Roofing
/ Waterproofing Membrane
62
Vegetated Roofs Extensive Green Roofs
Lightweight
Moderate Weight
Flowering Plants Soil
Sedum Media
2 4
4 6
Root Barrier / Drainage Mat Insulation Roofing
/ Waterproofing Membrane
63
Vegetated Roofs Extensive Green Roofs
Tray Systems
64
Vegetated Roofs Extensive Green Roofs
Hybrid Ballasted / Vegetated Roof
65
Vegetated Roofs Benefits Concerns
Benefits
Current Concerns
  • 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 may be difficult
  • Roof repair and maintenance may be difficult 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

66
Solar Roofs Clean Energy Production
Shiseido Windsor, NJ
Target Store Stockton, CA
67
Solar Roofs Benefits Concerns
Benefits
Current Concerns
  • 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 when
    needed

68
Green Materials Reducing Volatile Organic
Compounds (VOCs)
VOCs
Standard Roofing Adhesives
Source US EPA
69
Green Materials VOCs and Ground Level Ozone
Source US EPA
70
Green Materials Reducing Volatile Organic
Compounds (VOCs)
Low-VOC Alternatives
  • Water-based adhesives
  • High-solids adhesives
  • Urethane adhesives

71
Green Materials Low-VOC Alternatives
Alternative Water-Based High-Solids
Urethanes
Concerns Freezing, Slow Flash-Off Primer
Frequently Required Complicated Expensive
Typical Example Latex Paint Tapes Foam
Adhesive 2-Part Adhesive
72
Green Materials Construction Waste
Annual U.S. Landfill Waste
  • 160 Million Tons Of Construction Waste
  • 40 Million Tons of Roofing Waste
  • 25 of Total Construction Waste

Source US EPA (1998)
73
Green Materials Roof Membrane Recycling
Cookson Elementary School Troy, Ohio
1
2
Windrow Sweep
Cut Stack
4
5
Sieve Package
Grind
74
Roof Membrane Recycling Benefits Concerns
Benefits
Current Concerns
  • Landfill waste reduced
  • Overall environmental impact reduced
  • Economics do not currently support recycling
  • Only available in a regional pilot program for
    selected products
  • Logistics (removal, storage, transportation) are
    difficult
  • Recyclers must have an assured supply before end
    markets can be fully developed

75
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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