Los Angeles a Leader in Cool Roofing
9/3/2015
Los Angeles has long been a leader in culture, entertainment, and science. It now adds another credential to the list: green building. Los Angeles became the first major city to require cool roofing on all new roofs and roof replacements. This measure was decided on by the Los Angeles City Council to reduce energy use and energy costs, and to promote the health and wellness of Los Angeles residents and workers.
What Is A Cool Roof?
Cool roofing works by reflecting sunlight instead on absorbing it, and by shedding heat quickly in order to keep the roof temperature low. Cool roofs have been shown to significantly reduce roof temperatures—more than 50°F at the height of a hot summer day. If you’d like to learn more about cool roofing, visit our cool roof page in the resources below.
How Do Cool Roofs Work?
The “coolness” of a roof is determined by its SRI, or Solar Reflectance Index. The SRI is determined by looking at two factors:
- Solar Reflectance: This is the primary factor in determining how well cool roofing shingles function. Solar reflectance measures the amount of sunlight that is reflected rather than absorbed. A higher number means more sunlight is reflected, and the roof will stay cooler. This is also measured by its effectiveness over time, or “aged solar reflectance.”
- Thermal Emittance: This is the secondary factor; it measures a roofing material’s ability to release heat into the air. The more heat is released, the less heat is absorbed by your roof.
What Are The Green Roof Requirements for LA?
The LA Green Building Code requires the following criteria be met for all residential buildings:
| |
Min. 3-yr Aged Solar Reflectance |
Min. Thermal Emittance |
SRI |
| Steep-sloped roof (≤ 2:12) |
0.63 |
0.75 |
75 |
| Low-sloped roof (> 2:12) |
0.20 |
0.75 |
16 |
Notice that the cool roof requirements are different based on how steep your roof is. Make sure your roofing material meets the guidelines for the slope of your roof. If you're not sure about the slope of your roof, a roofing contractor should be able to assess your roof and explain your options.
The change to cool roofing will take some time-- it's only required on new roofs and complete roof replacements at this point. However, as cool roofing products become more common in the Los Angeles area, it will help reduce the heat island which often accompanies urban areas. Want to learn more? Check out our resources below.
Resources: