Cool Roof Policy Updates Trend in US Cities
By Sarah Schneider - Deputy Director, Cool Roof Rating Council
Due to the rise in extreme heat waves and increased urbanization, more and more cities across the globe are adopting policies and programs that require or encourage the installation of reflective roofing products on new and existing buildings. Commonly referred to as “cool roofs,” these building materials help mitigate urban heat island effect, which can have important implications when it comes to protecting public health and saving lives.
In the past 10 years, there has been a major uptick in cool roof and UHI policies by U.S. cities, and not just cities in the sunbelt. To date: Austin, Chicago, Chula Vista, California; Dallas, Denver, Houston, Los Angeles, Miami Beach, New York, Philadelphia, Los Angeles County and Washington, D.C., have all implemented cool roof mandates.
Some jurisdictions also require buildings to be LEED certified, such as Atlanta and Washington, D.C. Under LEED Version 4.1, up to two points can be awarded for the installation of a cool roof under the Sustainable Sites Credit for heat island reduction.
Many cities also encourage cool roofs through voluntary green building programs, income-qualified programs and financial incentives. Currently, Anaheim, California; Austin; Chicago; Los Angeles; Louisville, Kentucky; Pasadena, California; and Orlando offer a cool-roof rebate, while Baltimore; New York City; Philadelphia and San Antonio, Texas, deploy programs that install cool roofs on low-income homes.
The adoption of cool roofs can also be seen at the state level. California has had a prescriptive cool-roof requirement in its building code (Building Energy Efficiency Standards, Title 24, Part 6) since 2005. Alabama, Florida, Georgia, Hawaii, Nebraska and Texas also have building codes with cool-roof requirements. As states update their building codes, it’s possible that more of them will adopt energy-efficiency measures such as cool roofs.
During the day, a cool roof reflects solar radiation away from the building and, at night, releases any heat that was absorbed by the roof. In addition to combating urban warming, a cool roof also lowers the demand for air conditioning, decreases peak electrical demand and increases occupant comfort. Collectively, cool roofs also improve outdoor air quality and help with electrical grid stability. Cool roof materials also complement green and solar roofs.
Cool roofs are available in a variety of product types, including field-applied coatings and factory-coated metal. Historically, flat or low-sloped roofs were transformed into cool roofs by coating them white. However, there are now "cool color" products on the market that use darker-colored pigments that are highly reflective in the near infrared (non-visible) portion of the solar spectrum.
The “coolness” of a roof coating is determined by two basic properties: solar reflectance (sometimes called albedo) and thermal emittance. Solar reflectance is the fraction of solar radiation that is reflected away from the roof, while thermal emittance is the efficiency by which the roof can reradiate any heat that was absorbed into the building. The values of both properties range from 0- 1. In addition to these two metrics, the “coolness” of a roof can also be represented by its solar reflective index value, a calculated metric that combines solar reflectance and thermal emittance into one value. SRI values are usually between 0-100, with particularly cool materials exceeding 100.
With numerous products available for installation on commercial and residential buildings, identifying roofing materials that meet the needs of a project can be a daunting task. The CRRC’s Rated Products Directory is one resource for users looking to receive LEED credits, comply with building codes, or qualify for rebates or loans.
In addition to the CRRC’s work developing, implementing and communicating a radiative energy performance rating system for roof surfaces, the organization recently amended its bylaws to permit the rating of exterior wall products. Recent research by Lawrence Berkeley National Laboratory found that cool walls can save as much energy as a cool roof. The CRRC is currently exploring the development of a Wall Product Rating Program in collaboration with the wall industry.
About the Author
Sarah Schneider has been the Deputy Director of the Cool Roof Rating Council since 2013. She oversees the maintenance of the CRRC’s American National Standard (ANSI/CRRC S100) and accreditation to ISO/IEC 17065, and works closely with the CRRC Technical Committee; Ratings, Codes & Standards Committee; and Wall Rating Steering Committee. Schneider has a master’s degree in public policy and a Bachelor of Science degree in environmental science.