Courtesy Dicor Corporation
[Editor’s note: This information is provided by roof membrane manufacturer Dicor. While there’s plenty of “promotion” for their product included, some of the information and principles may be of assistance to our readers.]
Sometimes your RV needs a new roof. It could be because of age, or it could be because you backed under that tree branch and tore a hole in your roof that is not repairable, or it just could be that you want to change the look of your RV. When shopping for a new roof, one of the things you’ll want to consider is color.
The past few years have seen the growth of roof membrane colors like never before. There’s bright white, polar white, tan, gray, ivory, champagne, et al. Along with this preponderance of color has come discussion about “cool” roofs. That’s what we’ll be discussing today.
When you hear the term “cool” roof, what people are talking about is how well the roofing material is at reflecting and displacing solar heat in order to reduce the heat buildup in an RV. The bottom line is the better your roof is at reflecting light and dissipating heat, the cooler your living quarters will be and the less your air conditioning will need to work. That not only prolongs the life of your AC (your condenser runs less), but it also saves energy – and that’s good for the environment.
So how do you tell how “cool” an RV roof is? Well, sometimes helpful data is available. To show you what I mean, I’ll share some data from independent third party testing of Dicor’s Polar White DiFlex II™ TPO roofing. Dicor Polar White scored well in two attributes: Reflectivity and Solar Reflective Index. These two characteristics sound similar but they are quite different. Let me explain.
Reflectivity is the measurement of a material’s ability to reflect solar energy back into the atmosphere. It is like the expression: “Right back at you.” Light hits a surface and, instead of being absorbed, it is “reflected” back into the atmosphere. Reflectivity is measured as a percentage on a scale from 0 (hotter interior) to 100 (cooler interior). The higher the number the better, since it is reflecting more light. By this measure, DiFlex II Polar White earned an 86% rating. To put that into perspective, the reflectivity rating of acrylic white paint is 80%, while the reflectivity of aluminum is 61%.
Then there is the Solar Reflective Index (SRI), which measures a material’s ability to release residual heat that has been absorbed by the material. Remember, not all light is reflected – some of it is absorbed and that generates heat in the material. In short, it gets hot. Think about walking barefoot on the beach sand that has been in the sun all day. Ouch! SRI measures the ability of the material to send that heat back into the atmosphere. Think of the phrase: “Now get out.” Here Polar White received a 108 score on the high (cooler) side of the scale, compared to 100 for acrylic white paint and only 50 for aluminum.
The high reflectivity and SRI rating resulted in DiFlex II Polar White being listed by the Cool Roof Rating Council. (CRRC is a non-profit organization that implements and communicates accurate radiative energy performance rating systems for roof surfaces.) That’s quite a feat.
So should you avoid any of the other colors on the market today? Absolutely not! They all have their individual reflectivity and SRI values. Just keep in mind that darker colors absorb more light and generate more heat.