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