The concept behind cool roofs is really quite simple; light-colored or “cool” roofs reflect solar radiation (heat) while darker roofs absorb it, inevitably warming the building underneath and increasing the load on cooling systems. According to the California Consumer Energy Center, cool roofs can reduce surface temperature by up to 100 degrees Fahrenheit and drop cooling needs by a significant amount. On a communal scale, cool roofs are also a major player in reducing urban heat island effects.
So why aren’t roofs all over the country as white as the clouds that glide over them?
Well many commercial buildings do have white or light-colored roofs. Such buildings require an incredible amount of energy to cool, so minimizing heat gain is most definitely in the company’s best interest. Secondly, most commercial and industrial buildings have flat or low-pitched roofs, eliminating any aesthetic argument from the discussion.
Contrarily, on the steeper sloped roofs of most residential dwellings, aesthetics usually take the front seat over energy efficiency because homeowners typically want darker roofs, a notion supported by conventional roofing products themselves (asphalt, tile, wood shakes), which naturally lend themselves to darker pigments. In response, however, several roofing companies are developing “cooler” colors for their roofing products. Products that may not be as reflective as white or near-white shingles, but are a big step up from conventional choices.
So how do cool roofs, designed to reflect sunlight, jibe with solar panels, which are designed to absorb it?
Very well in fact. Rather than working against the panels, the reflectivity of cool roofs sends more light to the panels from all directions. While this may not do much in aiding flush mounted arrays and panels that are not in a position to absorb any of the reflected light waves, it certainly does not hurt.
Solyndra, for example, has created specially designed panels that absorb direct, reflected, and diffuse light.Yet Solyndra’s panels are specifically designed for commercial rooftops. And other unique designs, while versatile and built to take advantage of reflective surfaces, are as yet limited in scope of function.
So do we need solar panels designed for pitched but cool roofs or should the residence of the 21st century have a flat roof? Good question.In the meantime, there is no reason for the two to be at odds. Just like green roofs, there are other ways that a cool roof benefits a solar array. It goes like this: cool roofs reduce home cooling costs by a hefty margin and heating and cooling our the average home’s biggest energy consumers and solar electric systems work hard to provide that energy. Therefore savings on cooling equals savings on energy which equals an easier work day for the solar system and perhaps a smaller system to start with…which equals savings for your savings account.