Cool roofs is a term used to describe roofs that have high solar reflectance and high infrared emittance values that significantly lower the cooling load of the building, thus help reduce the building energy consumption. As reported by Oak Ridge National laboratory, cool can roofs save up to 40% in cooling costs.
Solar reflectance is the amount of solar radiation that a roof reflects. Cool roofs can achieve solar reflectance of over 70%. Reflected solar energy allows the roof to remain cooler, which means less heat is transferred into the building. For cool roofs the higher the value the better.
The infrared emittance of a roof is a measure of absorbed solar radiation that is emitted, or given off from the roof surface back into the sky. Emittance of metal roof can be as high as 90%. For cool roofs the higher the value the better.
Cool Roof Product Certification Programs:
Energy Star
In 1992 the US Environmental Protection Agency (EPA) introduced ENERGY STAR as a voluntary labeling program designed to identify and promote energy-efficient products to reduce greenhouse gas emissions.
Products that comply with the Energy Star criteria are eligible to carry the Energy Star label and are listed as an energy Star qualified product.
To meet the Energy Star requirements for low slope roofing (2:12 or less), the product must have an initial reflectivity of 0.65 and an aged reflectivity of 0.50 after three years of weathering. Reflectivity is not a function of product but of material.
To meet the Energy Star requirements for steep slope roofing (greater than 2:12), the product must have an initial reflectivity of 0.25 and an aged reflectivity of 0.15 after three years of weathering.
Butler® Colors:
Color |
Reflectance |
Aged |
Initial |
Energy Star Compliant |
|
Low Slope |
Steep Slope |
||||
Galvalume |
0.68 |
0.57 |
0.12 |
Yes |
Yes |
Birch White |
0.55 |
0.55 |
0.86 |
No |
Yes |
Shell Gray |
0.42 |
0.41 |
0.87 |
No |
Yes |
Solar White |
0.70 |
0.68 |
0.86 |
Yes |
Yes |
Solar Green* |
0.27 |
pending* |
0.85 |
*No |
*Yes |
Country Wheat |
0.51 |
0.50 |
0.86 |
No |
Yes |
Sandalwood |
0.34 |
0.34 |
0.87 |
No |
Yes |
Santa Fe Red |
0.22 |
0.21 |
0.86 |
No |
No |
Hunter Green |
0.09 |
0.09 |
0.88 |
No |
No |
Santa Ana Blue |
0.16 |
0.16 |
0.87 |
No |
No |
Terra Brown |
0.10 |
0.10 |
0.87 |
No |
No |
CRRC - Cool Roof Rating Council
The Cool Roof Rating Council was created in 1998 to develop accurate and credible methods for evaluating and labeling the solar reflectance and thermal emittance (radiative properties) of roofing products and to disseminate the information to all interested parties.
The CRRC is incorporated as a non-profit educational organization for the following purposes:
At the core of the CRRC is its Product Rating Program, in which roofing manufacturers can label various roof surface products with radiative property values rated under a strict program administered by the CRRC.
Solar White MR-24® has been processed by the Cool Roof Rating Council (CRRC). The information shown below will appear on the CRRC web site after the next update. The California energy efficiency standards require a CRRC rated cool roof for low slope roofs on conditioned buildings. The standards become effective October 1st. Butler now has a roof panel that meets the California requirements.
Company Name and Contact |
Brand |
Model |
Type |
Initial Solar Reflect. |
3-year Solar Reflect. |
Initial Therm. Emit. |
3-year Therm. Emit. |
Low-slope |
Steep-Slope |
CRRC Prod. ID |
Butler Manufacturing |
MR-24 |
Solar White |
Metal |
0.70 |
0.68 |
0.85 |
0.81 |
X |
X |
0756-0001 |
Helpful links:
http://www.epa.gov/heatisland/strategies/coolroofs.html
http://www.coolroofs.org/
http://www.coolmetalroofing.org/
http://www.energystar.gov/
http://www.coolmetalroofing.org