Cool Roof, California Title 24, Solar Reflectance Index (SRI)
What is Cool Roof?
A cool roof (or energy efficient roof) reflects and emits the sun’s solar energy back to the sky instead of absorbing and transferring heat to the building below.
“Coolness” is measured by two properties, solar reflectance and thermal emittance. Both properties are measured from 0 to 1 and the higher the value, the “cooler” the roof.
The California Title 24
Building Energy Efficiency Standards are designed to ensure new and existing buildings achieve energy efficiency and preserve outdoor and indoor environmental quality.
California has 16 climate zones that represent a geographic area for which an energy budget is established.
Solar Reflectance Index (SRI)
Solar Reflectance Index (SRI) is a measurement that combines a surface’s solar reflectance and thermal emittance. SRI is an indicator of how well a surface reflects (reflectance) and releases absorbed solar radiation (emittance).
The higher the SRI value, the lower its surface temperature and heat gain into a building will be. This helps reduce the urban heat island effect, as it requires less energy consumption from air conditioning systems.
North Country Unfading Green SRI Certified and California Title 24
In March 2018, at PRI Construction Materials Technologies, North Country Unfading Green slate was tested to determine the solar reflectance, thermal emittance, and solar reflectance index value. At the time of testing this color met the standard and Title 24 for medium and high wind conditions.
Test methods used included:
ASTM C 1549-16: Standard Test Method for Determination of Solar Reflectance Near Ambient Temperature Using a Portable Reflectometer.
ASTM C 1371-15: Standard Test Method for Determination of Emittance of Materials Near Room Temperature Using Portable Emissometers.
Both of these test methods are Energy Star, Leadership in Energy and Environmental Design (LEED), and Cool Roof Rating Council (CRRC) approved methods for determining radiative properties.
The solar reflectance index (SRI) was calculated in compliance with ASTM E 1980-11: Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surfaces.
Note: Testing was done for research purposes and was done to all the current standards at the time.
To request a copy of our North Country Unfading Green SRI Certified and California Title 24 laboratory test results, please email info@ncslate.com
