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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A New-Old Concept

Ballasted Roofs

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Ballasted Roofs

Simple

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Ballasted Roofs

Economical

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Ballasted Roofs

Protection

Albo Corporation, West Bend, WIBallasted Roof Installed in 1980

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1

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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Ballasted Roofs

Emerging Benefits

• Heat Island Mitigation

• Storm Water Retention

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Envelop Systems Research ApparatusOak Ridge National

Laboratories

Ballasted Roofs

Heat Island Mitigation

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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

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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

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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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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