What makes cool roofs so cool?

By Emma Peterson. 

Lauren Rogers of Sherwin-Williams shares cool roof coating basics and benefits. 

As energy costs rise and climate change continues to raise concerns about the planet, cool roof coatings have been developed as an innovative construction solution. These coatings are designed with advanced materials and pigments that allow them to, in comparison to traditional roofing materials, maintain lower roof surface temperatures. In this Read Listen Watch (RLW)® webinar, Heidi J. Ellsworth spoke to Lauren Rogers of Sherwin-Williams about these coatings and the benefits of maintaining a lower surface temperature.  

The first thing Lauren explained was that cool coatings reduce heat absorption in two ways, solar reflectance and thermal emittance. Solar reflectance is a surface’s ability to reflect solar radiation (sun rays). On the other hand, thermal emittance is how well a surface emits heat through infrared radiation. These two measurements, how much heat is reflected and how much is released, are what make up the solar reflective index measurement. Lauren explained, “The solar reflective index (SRI) is a calculated value that combines a material solar reflectance and thermal emittance into a single number. And typically, these SRI values range from zero to 100 and then a standard darkest black you can get will have an SRI of zero and then while a standard white pure white, it will have an SRI of 100.” 

These high SRI coatings are perfect for urban areas that are struggling with what is called the urban heat island (UHI) effect. Lauren explained, “Cool coatings are helping mitigate the urban heat island effect. For a basic definition, UHI is where urban areas are experiencing higher temperatures. So these cool roofs are helping mitigate and keep the temperatures of these urban areas a bit lower.” That’s not to say they can’t be a great option for more rural areas as well. In addition to lowering temperatures, these coatings can improve the durability of metal roofs against the effects of weathering.  

For contractors looking for those higher SRI coatings, the ones that will better reflect heat and stay cooler, they should look for products that have been certified by third-party labs like the Cool Roof Rating Council (CRRC). Lauren shared how Sherwin-Williams works with this group, saying, “SRI values are typically calculated in a lab. So often these values must be requested but are easy. Here at Sherwin, we calculate these at our Fort Myers, Florida facility. Then we have our values verified by the Cool Roof Rating Council, the CRRC, that is a third-party, non-biased source that vets and approves SRI values of coatings.” 

Read the transcript, Listen to the conversation or Watch the webinar to learn more about cool roofs and their benefits.