Most people think of a roof as something that protects from the rain, and a bad roof is referred to as a “leaky roof.” But in Southern California, there are other elements that beat down on the flat roofs of many commercial buildings more constantly and severely than rain: heat and sunlight. That’s where cool roofs come in. They protect structures from rain, but also greatly reduce heat – and consequently air conditioning and utility expenses.
One important characteristic to look for when choosing a cool roofing product is the material’s solar reflectance. This is a measurement of how well a surface material reflects sunlight. Not just the visible light we see, but also the infrared and ultraviolet wavelengths that heat up a building’s interior from above. Solar reflectance can also be called “albedo” (Latin for “whiteness”).
Another important term is emittance. Once a roofing material is heated up by the intense energy of the sun, how long will the roof hold onto that energy? A material with a high rate of emittance will release heat and help keep a building cooler than a material with a low rate of emittance.
Cool roofs are measured by a combination of solar reflectance and emittance – the Solar Reflectance Index (SRI). The SRI demonstrates how hot a surface would be relative to standard white or standard black surfaces. Materials with the highest SRI maintain the coolest roof.
One high quality roofing membrane is made by Sika and is called Sarnofil. Sarnofil has the best SRI in its class and is virtually impervious to water damage. It is rolled out in large sheets and hot welded at the seams. Sika is so confident in Sarnofil, that they warranty it even in the presence of ponding – a common site on flat roofs. While other roofing warranties contain exclusions for ponding, it will not compromise the Sarnafil roof system.
Of course, the right materials are only useful in the hands of the right installer. SunPower by Green Convergence has been installing Sika Sarnofil cool roofs for years in locations such as medical device giant Medtronic, the Paramount studio lot, and other large-scale commercial jobs across SoCal. Green Convergence has an in-house sheet metal fabrication department, which gives them much greater flexibility to address unique challenges presented by any roof, and they can provide solar solutions to go along with roofing when needed.