Most HVAC contractors are not also roofing contractors. They do, however, spend a lot of time on roofs, as that typically is where commercial buildings' cooling towers, air-cooled chillers, and air handlers are located. In warmer climates, HVAC-industry professionals have been exposed to cool roofs, which, along with LEDs, generally are low-hanging fruit in terms of overall ROI. The most common cool-roof strategies are vegetated roofs, non-vegetated reflective roofs, or a combination of the two. Here in South Florida, which is ASHRAE Zone 1, heat-island roof effect in our urban areas can impact building cooling costs by 20 to 70 percent and is estimated to be 5 to 10 percent of peak electricity demand for building cooling.
For those unfamiliar with heat-island effect, this is the absorption of heat by hardscapes—particularly, darker, non-reflective surface materials—and radiation to surrounding areas. Heat-island effect can be from roofs or non-roof (e.g., parking lots) sources. It is not uncommon for late-afternoon temperatures in downtown areas to be 7°F higher that those in outlying rural areas. Besides additional cooling costs, heat islands pose risks to human health from heat-related injuries, such as heat cramps, exhaustion, and heat stroke.
Green-building-rating-system reflective-roof credits generally require a high-albedo surface over a majority of roof area. For example, LEED 2009 for both new construction and existing buildings requires a Solar Reflective Index (SRI)—a measure of a material’s ability to reject solar heat, based on reflectance and emittance, with standard black equaling 0 and standard white equaling 100—of 78 or more for flat or low-sloped roofs and 29 or more for high-sloped (pitched) roofs. If you have a sloped roof, you can find shingles providing a SRI of 78 or more in a variety of colors, including shades of green, blue, and red. For flat roofs on commercial buildings—either a new roof or an existing roof that is to be painted or coated—the color choice is limited to shades of white (polar white, snow white, etc.).
That soon may be changing. In 2009, researchers at Oregon State University accidentally discovered a new color, a never-before-seen shade of blue they dubbed YInMn Blue after its three constituent elements: Yttrium (Y), Indium (In), and Manganese (Mn). The new pigment, commercially available from Shepherd Color Co., absorbs UV and is resistant to high temperatures. As a roof coating, it offers the promise of a cool and attractive roof. It’s still a bit pricey, and it probably will be a while before YInMn Blue offers as short a simple payback period—based on energy savings—as its more common white counterparts, but it’s a very cool—as in trendy—color. As my artist friend Erin Bassett noted when I mentioned I was writing about a never-before-seen color, I’ll never be a fashionista, but maybe I can be a fashioneer!