COOL ROOFING SUMMARY
Definitions:
Solar Reflectance – a measure of the ability of a surface material to reflect sunlight – including the visible,
infrared and ultraviolet wavelengths – on a scale of 0 to 1. Solar reflectance is also called "albedo."
Emittance – refers to a materials ability to release absorbed heat.
Solar Reflectance Index (SRI) – a value that incorporates both solar reflectance and emittance in a single
value to represent a material's temperature in the sun. SRI quantifies how hot a surface would get
relative to standard black and standard white surfaces. It is defined so that a standard black (reflectance
0.05, emittance 0.90) is 0 and a standard white (reflectance 0.80, emittance 0.90) is 100.
Materials with the highest SRI values are the coolest choices for roofing. Due to the way SRI is defined,
particularly hot materials can even take slightly negative values, and particularly cool materials can even
exceed 100.
Cool Roofing Programs
Energy Star®
Low slope1
Initial
Aged2
Steep slope
Initial
Aged2
Calif. Title 243
Low slope
Initial
Aged2
Green Globes
Low slope
Steep slope
USGBC LEED®
Low slope
Steep slope
ASHRAE
Solar
Reflectance
Emittance
Solar
Reflectance Index
0.75
75
0.65
0.50
0.25
0.15
0.70
0.63
784
29
0.70
1
0.75
784
29
Roof pitch 2/12 or less.
Three year field exposure. If CRRC testing for 3-year field aged reflectance is not available, it can be
derived using the California Title 24 calculation method for aged solar reflectance.
3
Requirement for conditioned spaces only.
4
Roughly equivalent to, for example, 0.65 reflectance and 0.90 thermal emittance, although a
number of different combinations of reflectance and emittance can achieve this value.
2
SIKA CORPORATION • ROOFING
100 Dan Road • Canton, MA 02021
Tel: 781-828-5400 • Fax: 781-828-5365 • usa.sarnafil.sika.com
Characteristics of Common
Roofing Systems1
Black EPDM
Smooth Bitumen
White Granular Surface
Bitumen
Dark Gravel on BUR
Light Gravel on BUR
White Thermoplastic
1
Sika Sarnafil’s
EnergySmart
Cool Colors
Sarnafil EnergySmart
White
Sarnafil EnergySmart
Tan
Sarnafil EnergySmart
Light Gray
Sarnafil EnergySmart
Patina Green
Sikaplan Fastened 45
EnergySmart White
Sikaplan Fastened 60
EnergySmart White
Sikaplan Adhered
EnergySmart White
1
2
Solar
Reflectance
0.06
0.06
0.26
Emittance
0.86
0.86
0.92
Solar Reflectance
Index
-1
-1
28
0.12
0.34
0.83
0.9
0.9
0.90
9
37
104
Lawrence Berkeley National Laboratory Cool Roofing Materials Database
Initial Solar
Reflectance
Aged Solar
Reflectance
Initial
Thermal
Emittance
Aged
Thermal
1
Emittance
Solar
Reflectance
Index
Aged Solar
Reflectance
Index
0.83
0.70
0.90
0.86
104
85
0.73
0.65
0.85
0.86
89
78
0.50
0.44
0.84
0.85
56
49
0.55
0.46
0.86
0.85
64
51
0.83
0.64
2
0.89
Pending
104
Pending
0.85
0.66
2
0.89
Pending
107
Pending
0.85
0.66
2
0.89
Pending
107
Pending
Applicable only to CRRC
Derived using the California Title 24 calculation method for aged solar reflectance
DOE Cool Roof Calculator
http://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htm
ENERGY STAR Roofing Comparison Calculator
http://rsc.ornl.gov/
Cool Roof Benefits







Potential to reduce A/C tonnage
Lower cooling costs
Improved occupant comfort
Longer roof life
Urban heat island mitigation
Less smog
Lower peak demand on the electricity grid
SIKA CORPORATION • ROOFING
Listings
Approved
Slope
CRRC &
Energy Star
CRRC &
Energy Star
CRRC &
Energy Star
CRRC &
Energy Star
CRRC &
Energy Star
CRRC &
Energy Star
CRRC &
Energy Star
Low &
Steep
Low &
Steep
Steep
Steep
Low &
Steep
Low &
Steep
Low &
Steep
Cost Savings
Americans spend about $40 billion annually to air condition buildings – one-sixth of all electricity
generated in this country. White, reflective roofing can help reduce the amount of air conditioning
needed in buildings, and can reduce peak cooling demand by 10 - 15% and can provide 10% - 20% air
conditioning cooling savings for the building owner. This could possibly save 30 -40 mega watts per year
in California.
Case Study
“Measured Energy Savings and Demand Reduction from a Reflective Roof Membrane on a Large Retail
Store in Austin”, Ernest Orlando Lawrence Berkeley National Laboratory, June 2001, LBNL-47149.
The study measured and documented summertime air-conditioning daily energy savings and demand
reduction from a reflective roof membrane retrofit on a large retail store (100,000 sq. ft.) in Austin,
Texas. The original black rubber (EPDM) membrane was replaced with a white thermoplastic membrane
with the following results:
-
decrease in average maximum roof surface temperature from 168oF to 126oF
-
estimated total annual energy savings of $7,200
-
estimated present value of future abated expenditures of $61,000 to $71,000 over a conservative
roof life estimate of 13 years
Federal and State Rebate & Incentive Programs
Established in 1995, the Database of State Incentives for Renewable Energy (DSIRE) is an ongoing project
of the Interstate Renewable Energy Council (IREC), funded by the U.S. Department of Energy and
managed by the North Carolina Solar Center. The website provides a comprehensive listing of federal,
state and local energy efficiency and renewable energy rebate and incentive programs.
http://www.dsireusa.org/
SIKA CORPORATION • ROOFING