Solar Reflectivity Issue

Background

In 1998, the Cool Roof Rating Council (CRRC) developed a Cool Roof Coating Standard (ANSI/CRRC S100) that requires roof coatings to achieve certain solar reflective values. This program has been widely adopted into various building codes and greenbuilding standards in much of the United States. This standard resulted in a shift to only being able to utilize light colored coatings and/or solar reflective engineered pigments. The CRRC initiated the process to revise the ANSI/CRRC S100 standard (CRRC S100) in fall 2023, beginning with the formation of the CRRC Consensus Body. The S100 standard is being updated to cover specimen preparation and test methods for measuring the initial and aged solar reflectance and thermal emittance of exterior wall coating products. ACA is actively participating in the update of the standard as a voting member of the Consensus Body.

CRRC released their Wall Product Rating Program in January 2022. Similar to their current Roof Rating Program, the Wall Product Rating Program rates exterior wall products based on the surface radiative properties such as solar reflectivity and thermal emittance levels. In September 2022, the CRRC released their Wall Products Directory, a publicly available database for the radiative properties of exterior wall products. ACA currently sits on the Cool Wall Rating Council’s (CRRC) Wall Product Rating Program’s Technical Committee and provided technical support during the development of the new program to ensure the program requirements are achievable for our industry. As minimum solar reflectivity requirements for walls are being adopted into building codes and green building standards, the type of pigments currently used in exterior wall coatings will likely shift to lighter colors or result in the increased use of solar reflective engineered pigments. The CRRC is updating their ANSI/CRRC S100 “Standard Test Methods for Determining Radiative Properties of Materials” standard that serves as the basis of their methods for rating the surface radiative properties of both roof and exterior wall coatings. ACA was accepted to participate in the consensus body and will review the technical work as the standard is updated. ACA has reinstated the Solar Reflectivity work group to discuss the technical aspects of the standard and continue to address any upcoming changes to green building codes around this issue.

ACA is continuing to actively monitor the addition of potential requirements for the use of solar reflective wall products in green building codes. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) finalized an addendum to expand Standard 90.1-2019 by adding requirements for south, east, and west-facing walls to have a minimum solar reflectance of 0.30 in climate zone 0. The U.S. Green Building Council (USGBC) approved a proposed LEED pilot credit for solar reflective wall coatings that gives credit when solar reflective coatings with a minimum solar reflectance of 0.60 and a thermal emittance of 0.75 are used. The National Association of Home Builders (NAHB) recently included reflectance requirements for walls in the 2020 edition of the National Green Building Standard (ICC/ASHRAE 700). The state of Hawaii has included minimum solar reflective requirements into their energy code and is the first US state to do so. The International Energy Conservation Code (IECC) was updated to include a reference to ASHRAE 90.1 Addendum S. Given how reliant many green building codes are on ASHRAE 90.1, we are likely to see this Addendum S added into several green building codes and standards over the next code cycle. ACA will continue to monitor for any proposals relating to solar reflective requirements.

Given the focus on climate change and limiting the urban heat island effect, the CRRC is considering creating a Pavement Coatings Program. Several cities in the US have started pavement pilot programs to test their effectiveness in limiting the urban heat island effect. The CRRC anticipates that the need for solar reflective pavement coatings will increase as cities work to limit overheating due to climate change. The pavement coating program would be similar to both the roof and wall coatings program.

In 2023, ACA’s Katherine Berry was elected to the CRRC’s Board of Directors. ACA will continue to work with the CRRC to ensure their roof and wall product rating programs are technically sound and achievable for our industry.

ACA Action

ACA will continue to provide technical and industry expertise to the CRRC through the Board of Directors and the Wall Product Rating Program Technical Committees to ensure the program continues to be achievable for our industry. ACA will continue to monitor for the addition of minimum solar reflectivity requirements for coatings used on walls and roofs in green building codes and standards.

ACA Staff

Katherine Berry
Director of Sustainability & Environment