Understanding Cool Coatings

“Coolness” is measured by two properties, solar reflectance and thermal emittance. Both properties are measured from 0 to 1 and the higher value, the “cooler” the roof. Solar Reflectance Index (SRI) calculates these two values (solar reflectance and thermal emittance) to determine the roof and wall’s ability to reject solar heat.

• Solar Reflectance (SR): The ability to reflect a percentage of solar radiation from the surface back into the atmosphere.
• Thermal Emittance (TE): The ability to radiate a percentage of absorbed solar energy (heat) back into the atmosphere.
• Solar Reflectance Index (SRI): A calculation method using solar reflectance and thermal emittance values to determine the roof’s ability to reject solar heat.

Learn more about cool coatings here: 

• Metal Roofing Alliance (MRA)
• Cool Roof Rating Council (CRRC)

Solar Reflective Coatings Help Keep It Cool

Sherwin-Williams offers roof reflective coatings for both coil and extrusion with pigments altered physically and chemically to reflect infrared radiation while absorbing the same amount of visible light. The result is that both the coating and the metal roof stay cooler, while maintaining color retention.

Sustainability Benefits of Cool Coatings

Cool roofing and wall panel requirements appear in national and local energy codes, sustainable building initiatives, and energy rebate programs. Higher SRI Values contribute to lower surface temperatures, reducing ambient air temperatures, thereby mitigating the urban heat island effect. Urban heat islands are caused by roof and pavement surfaces retaining the suns’ heat, causing elevated temperatures, increased greenhouse gas (GHG) emissions, and local climate disruptions. Cool coatings minimize these adverse effects, while increasing occupant comfort and reducing the occurrence of health issues associated with poor air quality and smog. When used in new construction, cool coatings systems offer opportunities to earn LEED credits such as:

1. Building product disclosure and optimization - material ingredients
2. Building product disclosure and optimization - environmental product declarations
3. Building life cycle impact reduction
4. The heat island reduction – roof and wall

When you design with sustainability in mind, it is crucial to use products and suppliers that offer you the resources and solutions to help you meet your goals. At Sherwin-Williams Coil Coatings, we work directly with our customers to help their projects meet sustainability requirements of national and global initiatives.

Applications and Use Cases for Solar Reflective Coatings

Cool coatings can be applied to a number of pre-treated substrates, including Galvalume® aluminum, and Hot-Dipped Galvanized (HDG) steel and can be applied to the following building products: