Do you know why it’s important to know the solar reflective index of your commercial flat roof?
When your commercial roof has reached the end of its life cycle or has been damaged beyond repair, it’s time to decide what type of new roofing system is best suited to your needs. In the past 20 years, with rising energy costs, roofing manufacturers, government agencies, and consumers have started to focus on keeping energy costs down. One of the most effective ways of doing this is to choose a “Cool Roof”, and the easiest way to ensure that you are choosing the highest-performance cool roof is to look at the Solar Reflective Index (SRI).
The SRI is a simple yet comprehensive way of qualifying a cool roof with a single, easy-to-read number value. The SRI is expressed in digits from 0 to 100, with a higher number meaning a cooler roof. The SRI is measured twice – once when the roof is brand new, and again after 3 years. It was developed by the Lawrence Berkeley National Laboratory and is the result of many measurements input into a rather complicated mathematical formula. As a building owner on the market for a new commercial roof, all you need to do is look at the SRI value for the roofing system that you are considering, without having to decipher and interpret a lot of technical roofing and physics terminology.
The Cool Roof Rating Council (CCRC), an independent organization that verifies and labels cool roofing products, has endorsed the Solar Reflective Index as the best method of certifying a cool roof. They do continue to use the older rating method as well, which involves taking two measurements — how well the roof surface can reflect light energy (solar reflectance) and how quickly the surface releases absorbed heat (thermal emissivity). This 2-value measuring system was fairly effective and gives a general idea of how energy-efficient a “cool roof” will be, but it has several limitations. For example, a roofing system might have high solar reflectance and poorly release absorbed heat. Or it might not reflect the sun very well, but it is great at releasing absorbed heat. Which is better? What about winds over the roof surface, or insulation in contact with the roofing materials? The old method leaves us scratching our heads.
If you are considering a new Cool Roof for your building and would like to know more about the Solar Reflective Index, including a rating of specific roofing systems by manufacturer, you can visit the Cool Roofs Directory at Coolroofs.org.
The table below gives a general overview of the SRI values of common types of commercial roofing systems.
|Roofing System||SRI||3-yr SRI|
|Single Ply PVC, white||108||90|
|EPDM, standard black||-3||-3|
|Asphaltic Membrane, white||32||27|
Reach out to Complete Commercial Roofing, we’d be happy to answer any additional questions you have about this topic. Call 765-457-4848 today!