Possibly one of the easier and less-invasive ways to industrial sustainability is through the use of cool roofs.
Making a rooftop “cool” can be as easy as painting on a coat of white paint to reflect light and heat instead of absorbing it into a building. Using improved reflective roof coatings instead of conventional roofing materials when replacing or resurfacing a roof can reduce air conditioning costs and greatly minimize energy use.
If starting from scratch and constructing a building from the ground up, installing a cool roof is a great first step; in most circumstances, there are no additional costs than those of a traditional roof.
"‘Cool roofs’ are one of the quickest and lowest cost ways we can reduce our global carbon emissions and begin the hard work of slowing climate change,” says former United States Secretary of Energy Steven Chu.
Having a cool roof not only enhances durability but also reduces cooling load buildup and the “urban heat island effect,” a condition in which cities are considerably warmer than their surrounding rural areas. Some buildings are also exploring green roofs in an effort to make urban areas more sustainable.
Cool Roofing Methods and Applications
Roof systems are composed of multiple layers, but it’s the outermost sun-exposed layer that gives a roof “cool” properties. According to the Department of Energy’s guidelines for selecting cool roofs, dark roofs absorb 90% or more of incoming solar energy, potentially reaching temperatures of higher than 150°F (66°C) during sunlight hours. Light colored roofs absorb less than 50% of that solar energy.
A cool roof coating is applied similarly to a very thick paint and is a very effective energy efficient option; it doesn’t even necessarily have to be white. A cool dark color reflects more sunlight (40%) than a similar conventional dark color (20%), but still less than a light-colored surface (80%). Cool roof coatings also offer protection from UV rays, chemicals, and water, and can ultimately extend a roof’s life.
For low-sloped roofs, pre-fabricated single-ply membrane sheets can be applied to the roof with mechanical fasteners, adhesives, or ballasts like stones or pavers. Built-up cool roofs can be constructed by embedding gravel in a flood coat of asphalt, or by applying a mineral surfaced sheet (i.e. a modified bitumen sheet membrane) with reflective mineral granules or with a factory-applied coating.
Another efficient cool roof solution is spray polyurethane foam. Two liquid chemicals are mixed together which expand to form a thick solid material resembling Styrofoam. This adheres to the roof and a protective cool coating is then applied.
An eco-solution for steep-sloped roofs is cool shingles. Most types of asphalt, wood, polymer, or metal shingles can be coated during factory production to give more reflective qualities. Clay, slate, or concrete tile roofs can be naturally reflective or can be treated to provide additional protection. Unpainted metal is a good solar reflector but bad thermal emitter so it would have to be painted or covered with a cool reflective coating to achieve cool roof status.
Solar panels are an incredibly green solution but don’t usually provide enough roof weather protection to be considered a cool roof solution. Many roofs are also not suitable for solar panel installation. Building-applied photovoltaics (solar panels built for roofing) could be the answer, but this is still being further researched.
Storming the global cool roofs market are key players Owens Corning, CertainTeed Corporation, GAF Materials Corporation, TAMKO Building Products Inc., IKO Industries Ltd., ATAS International Inc., Henry Company, PABCO Building Products, LLC., Malarkey Roofing, and Polyglass S.p.A. These companies are up-to-date on cool roof innovations, and using state-of-the-art technology such as drones to detect problem areas and identify safety hazards; they show customers the best green solutions.
With the massive rise in the interest and demand for sustainability, cool roofing technologies are constantly being updated and developed.