An energy-efficient roof has the ability not just to regulate the attic temperature but also to prevent the sun from compromising indoor comfort levels. Many manufacturers advertise their products as “cool”, but which ones are cool enough to really make a difference?
To help you choose the roofing system with excellent, long-term performance, Lone-Star Roof Systems explains the concepts you should know to measure energy efficiency:
What Is Reflectance?
Reflectance measures how well the roofing material can bounce solar heat back into the sky. On a scale of 0 to 1, a higher decimal number means better reflectance. Inefficient roofs absorb most of the energy the sun throws at them, but the “cool” ones block the heat because of their high solar reflectance values.
Generally, light-colored roofs are “cooler” than dark-colored ones. However, any experienced roofing contractor would tell you that some energy-efficient products come in bold hues for better curb appeal. The best examples are CertainTeed’s Landmark Solaris® PLATINUM and GAF’s Timberline® Cool Series® asphalt shingles.
What Is Emittance?
Emittance refers to the ability of the roof to cool itself after absorbing heat, which is also measured the same way as solar reflectance. Roofing materials with high thermal emittance values are good at giving off the sun’s energy rather than retaining it.
What Is the Solar Reflectance Index?
The SRI is the standardized measurement that rolls the roofing material’s reflectivity and emissivity properties into one. The scientists at Lawrence Berkeley National Laboratory developed it using the complex formula as per ASTM E 1980. By combining the two thermal properties, you only need to look for a single value to know how energy-efficient the product is.
Although most manufacturers still report reflectance and emittance information separately, the SRI has gained currency since the Cool Roof Rating Council began using it. Professional roofers would also tell you that the U.S. Green Building Council utilizes it for evaluating cool-roofing products.
At Lone-Star Roof Systems, we give you access to an impressive selection of roofing options to help you achieve your energy efficiency goals. Call us at (855) 520-0909 today to talk about your needs in Bryan or Huntsville, TX, and to get an estimate.