cool roofing… cutting through the glare may 12, 2005 atlanta, ga compiled by…

Cool Roofing…Cutting Through the Glare

May 12 , 2005

Atlanta, GA

Compiled by…

Sponsored by

– Roof Consultants Institute Foundation (RCIF)

– Oak Ridge National Laboratories (ORNL)

– National Research Council of Canada (NRC)

Attended by

– Over 200 construction and design professionals

– Industry media & trade associations

Presented by

– 30 researchers from universities, government, industry

Cool Roofing…Cutting Through the Glare

Environmental Issues

Design Issues

Economic Issues

Cool Roofing…Cutting Through the Glare

Key Symposium Topics

Highly reflective roofs can reduce urban temperatures in the summer….

Reducing ozone formation

Reducing energy costs

Reducing fossil fuel demand

Cool Roofing…Cutting Through the Glare

Cool Roofs & the Environment

….. but the cooling effect of highly reflective roofs may be overstated

– Wind effects not always considered

– Degradation due to roof aging not fully addressed

– Alternative approaches not always considered

Cool Roofing…Cutting Through the Glare

Cool Roofs & the Environment

Cool Roofing…Cutting Through the Glare

Cool Roofs & Wind Effects

The Effects of Wind on Roof Surface Air Temperature

31

29

27

25

23

Air

Tem

per

atu

re (

oC

)

Roof Reflectivity (%)

0 10% 20% 30% 40% 50% 60% 70% 80%

Summertime Daily Average and Maximum Air Temperatures for Roof System Reflectivity Simulations Conducted for City of Chicago

Source: Study on roof system reflectivity and near-surface air temperatures in Chicago, IL (DuPuis & Graham)

No WindWith Wind Effect Added

Cool Roofing…Cutting Through the Glare

Cool Roofs & Surface Aging

Highly-Reflective (50%)

Semi-Reflective (20%)

Low-Reflective (5%)

White membranes

Grey, tan, mineral surfaced, and ballasted membranes

Black membranes

Ref

lect

ivit

y (%

)

Exposure (Years)

Roof Reflectance After Field ExposureOak Ridge Laboratories Envelope Systems Research Apparatus (ESRA)

Cool Roofing…Cutting Through the Glare

Cool Roofs & Surface Aging

Professional Roofing, May, 2005

Roofing’s Dirty Secret

A Roof Consultant Takes The Industry To Task for Dirty Roofs

Houston Chronicle, May 26, 2003

Astros cry foul over park roofClaim filed over ugly growth

The roof of Minute Maid Park is growing like a Chia Pet

Reflective Membranes

Reflective Coatings

Garden Roofs

Ballasted Roofs

Cool Roofing…Cutting Through the Glare

Cool Roofs: Design Options

Durability

Maintenance

Glare

Cool Roofing…Cutting Through the Glare

Design Issues

What does it mean for the building owner?– Scaling down the economics to the individual owner of

a specific building

Are there regional differences?– Warm versus cold regions

– Sunny versus cloudy regions

– Regional fuel cost differences

What about operating costs?– Cleaning costs

– Reflectivity versus insulation

Cool Roofing…Cutting Through the Glare

Economic Issues

The Economics of Cool Roofing:A Local and Regional Approach

James L. Hoff

The Economics of Cool Roofing

Cool Roofing & The Building Owner

What are the economics of cool roofing……

1) For an individual building owner

2) In a specific location

The Economics of Cool Roofing

Potential Misunderstandings

Measurement Scale

Regional Differences

The Economics of Cool Roofing

How Scale May Affect Perception

Potential net annual energy savings using reflective roofs

Source: Lawrence Berkeley National Laboratory Heat Island Group

City Of Chicago:$10 Million

The Economics of Cool Roofing

How Scale May Affect Perception

Source: DOE Cool Roof Calculator

Potential net annual energy savings using reflective roofs

A 20,000 Sq. Ft. Building in Chicago

$20

The Economics of Cool Roofing

Regional Differences

Climate

Energy Costs

The Economics of Cool Roofing

Climatic Differences

Climate Metric

Heating Degree Days

Cooling Degree Days

Solar Load(BTU/ Sq. Ft. / Day)

U.S. Low*

141 (Miami)

69 (San Francisco)

1061 (Seattle)

U.S. High*

7521(Milwaukee)

4127 (Miami)

1839 (Phoenix)

Variance

5234%

5881%

73%

* For Standard Metropolitan Statistical Areas

Source: DOE Cool Roof Calculator

The Economics of Cool Roofing

Energy Cost Differences

Energy Source

Electricity($ / KWH)

Natural Gas($ / Therm)

U.S. Low*

$0.0558(Louisville)

$0.0724(Salt Lake City)

U.S. High*

$0.1236(New York City)

$1.2500(Atlanta)

Variance

122%

73%

* For Standard Metropolitan Statistical Areas

Source: Energy Information Administration, June, 2004

The Economics of Cool Roofing

Study Objectives

Adjust the scale to fit the end-user

Compare local differences in climate & energy cost

Develop a simple, but informative graphic representation

The Economics of Cool Roofing

Methodology

Local Climate Inputs

Local Energy Costs

Regional Locations

Building Parameters

The Economics of Cool Roofing

Local Climate Inputs

DOE Cool Roof Calculator

Heating Degree Days

Cooling Degree Days

Solar Load

The Economics of Cool Roofing

Local Energy Costs

Electricity EIA commercial electricity costs by state

(June, 2004)

Natural Gas EIA commercial natural gas costs by state

(June, 2004)

The Economics of Cool Roofing

Regional Locations

Portland

Boston

New York

Pittsburgh

Baltimore

Cleveland

Detroit

Indianapolis

Chicago

Milwaukee

Minneapolis

Richmond

CharlotteNashville

Atlanta

St. Louis

Little Rock

Jacksonville

Miami

TampaNew Orleans

Houston

Ft. Worth

Phoenix

Boulder

Cheyenne

Boise

Reno

Portland

Seattle

SLC

Las Vegas

Los Angeles

AlbuquerqueOk. City

Louisville

Birmingham

Kansas City

San Francisco

40 Major Cities Across United States

The Economics of Cool Roofing

Building Parameters

55% Reflectance

80% Emittance

Elec. Cooling (COP = 2.0)

Gas Heat (70% Efficiency)

5% Reflectance

80% Emittance

Elec. Cooling (COP = 2.0)

Gas Heat (70% Efficiency)

R-20 Insulation R-20 Insulation

20,000 Sq. Ft. 20,000 Sq. Ft.

v.

Portland

Boston

New York

Pittsburgh

BaltimoreCleveland

Detroit

Indianapolis

Chicago

Milwaukee

Minneapolis

Richmond

CharlotteNashville

Atlanta

St. Louis

Little Rock

Jacksonville

Miami

TampaNew Orleans

Houston

Ft. Worth

Phoenix

Boulder

Cheyenne

Boise

Reno

Portland

Seattle

SLC

Las Vegas

Los Angeles

AlbuquerqueOk. City

Louisville

Birmingham

Kansas City

San Francisco

$0$100$200

$300$400$500

$0$100$200

$300$400$500

Annual Heating / Cooling Cost Savings:

Reflective Roof versus Non-Reflective Roof

(-$50)

(-$100)

(-$50)

(Dollars per 20,000 Sq. Ft. Roof Area / R-20 Insulation)

Portland

Boston

New York

Pittsburgh

BaltimoreCleveland

Detroit

Indianapolis

Chicago

Milwaukee

Minneapolis

Richmond

CharlotteNashville

Atlanta

St. Louis

Little Rock

Jacksonville

Miami

TampaNew Orleans

Houston

Ft. Worth

Phoenix

Boulder

Cheyenne

Boise

Reno

Portland

Seattle

SLC

Las Vegas

Los Angeles

AlbuquerqueOk. City

Louisville

Birmingham

Kansas City

San Francisco

Annual Heating / Cooling Cost Savings:

Solar Load Effects

High Solar Loads Push Bands Northward

Portland

Boston

New York

Pittsburgh

BaltimoreCleveland

Detroit

Indianapolis

Chicago

Milwaukee

Minneapolis

Richmond

CharlotteNashville

Atlanta

St. Louis

Little Rock

Jacksonville

Miami

TampaNew Orleans

Houston

Ft. Worth

Phoenix

Boulder

Cheyenne

Boise

Reno

Portland

Seattle

SLC

Las Vegas

Los Angeles

AlbuquerqueOk. City

Louisville

Birmingham

Kansas City

San Francisco

Annual Heating / Cooling Cost Savings:

Solar Load EffectsLow Solar Loads Push

Bands Southward

The Economics of Cool Roofing

Local Energy Price Effects

Metric

Heating Degree Days

Cooling Degree Days

Electricity ($/KWH)

Annual Savings

New York City

5090

1002

$0.1236

$360

Salt Lake City

5636

1054

$0.666

$160

The Economics of Cool Roofing

Local Energy Price Effects

Metric

Heating Degree Days

Cooling Degree Days

Electricity ($/KWH)

Annual Savings

Baltimore

4912

1133

$0.0947

$280

Richmond

4097

1297

$0.585

$160

The Economics of Cool Roofing

Reflectivity Effects

City

Seattle

Detroit

Indianapolis

Charlotte

Phoenix

55% Reflectivity

(-$100)

$0

$60

$260

$860

75% Reflectivity

(-$160)

-($20)

$60

$340

$1,160

Annual Savings (Loss)

Change

(-60%)

n/a

n/c

30%

35%

The Economics of Cool Roofing

Study Limitations

Demand Charges

Non-Air-Conditioned Buildings

Calculator Accuracy / Validity

Portland

Boston

New York

Pittsburgh

BaltimoreCleveland

Detroit

Indianapolis

Chicago

Milwaukee

Minneapolis

Richmond

CharlotteNashville

Atlanta

St. Louis

Little Rock

Jacksonville

Miami

TampaNew Orleans

Houston

Ft. Worth

Phoenix

Boulder

Cheyenne

Boise

Reno

Portland

Seattle

SLC

Las VegasLos

Angeles

Albuquerque

Ok. City

Louisville

Birmingham

Kansas City

San Francisco

$0$100$200

$300

$400

$500

$0$100$200

$300$400$500

(-$50)

(-$100)

(-$50)

The Economics of Cool Roofing

Reflective Roofs & The Building Owner

Where will the economic payoff stimulate investment?