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New Heat Mitigation and Water Retention Concepts to Expand Green Roofing Demand
Greening Rooftops for Sustainable CommunitiesJune 4, 2009Atlanta, GA
James L. Hoff, DBAResearch Director
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Windrow & Sweep
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Cut & Stack
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Chop
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Grind Sieve & Package
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Recycle
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Ballasted Roofs
Easily Recycled
Source: EPDM Roofing Association
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Ballasted Roofs
Historic Benefits
• Economical
• Durable
• Recyclable
Low Initial Cost
Low Life Cycle Cost
Low Environmental Impact
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Envelop Systems Research ApparatusOak Ridge National
Laboratories
Ballasted Roofs
Heat Island Mitigation
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10
Hour
OF
Black EPDM
Light Ballast (10#)
Med. Ballast (17#)
Heavy Ballast (21#)
White TPO
Concrete Paver
Painted Paver 1
Painted Paver 2
Ballasted Roofs
Heat Island Mitigation
Average Roof Membrane Temperature By Hour
Source: Desjarlais, Petrie & Atchley, 2008
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Black EPDM
Light Ballast (10#)
Med. Ballast (17#)
Heavy Ballast (21#)
White TPO
Concrete Paver
Painted Paver 1
Painted Paver 2
Hour
BT
U /
(H
X S
q.
Ft.
)
Ballasted Roofs
Heat Island Mitigation
Average Heat Flux By Hour
Source: Desjarlais, Petrie & Atchley, 2008
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• California Title 24 (Min. 21 # / sq. ft.)
• Chicago Energy Code (Min. 15# / sq. ft.)
Ballasted Roofs
Heat Island Mitigation
Now Recognized By…
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Ballasted Roofs
Storm Water Retention
Source: Carlisle Construction Products Source: GreenGrid® EcoBallast ® Systems
Retention Mat Option Interlocking Tray Option
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Ballasted Water-Retaining Roof
Extensive Green Roof
Smooth Stone Ballast
(2” to 4”)
Planting Medium( 2” to 6”)
Moisture-Retention Mats
(1 or 2)Moisture-Retention Mats(1 or 2)
Drainage BoardProtection MatRoof Membrane
Roof Insulation
Roof Deck
Drainage BoardProtection Mat
Roof Membrane
Roof Insulation
Roof Deck
Storm Water Retention
Retention Mat Option
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Modular Ballasted Water-Retaining Roof
Modular Extensive Green Roof
Smooth Stone Ballast
(2” to 4”) Planting Medium( 2” to 6”)
Protection MatRoof Membrane
Roof Insulation
Roof Deck
Protection MatRoof Membrane
Roof Insulation
Roof Deck
Interlocking TrayInterlocking Tray
Storm Water Retention
Interlocking Tray Option
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Ballasted Roofs
Water Retention Testing
Water Retention Test Apparatus
Architectural Testing, Inc.York, PA
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Rain Event
1” / Hour
2” / Hour
4” / Hour
Single Retention Mat
22.4%
6.2%
5.9%
DoubleRetention Mat
37.8%
11.5%
5.6%
Percent Water Retention: Three Hours After Simulated Rain Event
Ballasted Roofs
Water Retention Testing
Source: Architectural Testing, Inc., 2008
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The Opportunity
Integrating Green & Ballasted Roofs
$0.00
$2.00
$4.00
$6.00
$8.00
$10.00
$12.00
$14.00
$16.00
$18.00
0
50
100
150
200
250
300
350
400
450
Installed Cost($US / Sq. Ft.)
Annual Sales(Millions of Sq. Ft.)
Green Roof Ballasted Roof
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The Future
Hybrid Green / Ballasted Roofs
Ballasted Areas Retain Storm Water Reduce Summer Temperatures and Add Wind, Fire & Traffic Resistance
Vegetated Areas Reduce Summer Temperatures and Retain, Transpire and Cleanse Storm Water
Tapered Roof Design Directs Storm Water
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Hybrid Green / Ballasted Roofs
Future Research
• Green / ballasted storm water testing and modeling
• Hybrid systems energy modeling
• Economic analysis to optimize benefit / return
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