Reflective Roofing Systems Save Energy at Federal Facilities
April 1, 2002
California's Edwards Air Force Base and San Diego Naval Base Marine Barracks are taking advantage of reflective roofing systems. The new roofing systems, which have been installed on existing facility buildings, serve to waterproof, insulate, and keep low-slope roof surfaces cool. Energy savings are achieved through the innovative use of technology to coat a roof with a durable, new surface. The high level of infrared emittance of the new surface, in combination with its high solar reflectance, can reduce peak surface temperatures by more than 35 percent. Depending on the level of conventional insulation in the roof, decreases in the heat flow through the roof can be equally dramatic.
The coating exceeds the requirements of the ENERGY STAR® roof products program and provides a low-slope roof with initial high solar reflectance (81 percent). For products suitable for both low-slope and steep-slope applications, the ENERGY STAR>® roof products program requires initial solar reflectance greater than 65 percent. (See www.energystar.gov/products/, then click on "Roof Products.")
By using this system, the U.S. Army Corps of Engineers, who is responsible for the maintenance of the facilities at the San Diego Naval Base, has qualified for an energy rebate from the State of California. The rebate was earned from California's Energy Initiative Rebate Program for the reduction in energy consumption that is expected as a result of the application.
On new roofs, a sprayed-on polyurethane foam (SPF) base provides insulation, structure, and contour for drainage. However, unprotected polyurethane foam, even when covered with a gravel topcoat, will deteriorate due to ultraviolet light. It is also prone to water damage, erosion, drying, cracking, and attack by birds. When used alone, SPF requires frequent maintenance, re-sealing, and cleaning.
The application of polyurea permanently seals the SPF base with a seamless, flexible, extremely tough membrane with excellent water and chemical resistance. TOTALSHIELD™ polyurea, for instance, has the additional advantage that it can be applied to vertical as well as horizontal surfaces with equal effectiveness.
A final topcoat of a highly reflective coating with small hollow borosilicate spheres provides a sealed, bonded surface with high solar and ultraviolet reflectance and high infrared emittance. It protects both the polyurethane foam and the polyurea from solar and ultraviolet damage. The National Aeronautics and Space Administration developed the hollow borosilicate spheres for use in the thick insulating tiles that protect the space shuttle upon re-entry into the atmosphere. Use of these spheres in reflective roof coatings is an example of the transfer of space technologies to the benefit of the general public.
At Edwards Air Force Base and San Diego Naval Base, the roofing system was first encapsulated through the application of a primary coat of polyurea. This precludes the need to remove hazardous materials, including asbestos, while conforming to all Federal, State, and local environmental and code requirements. An additional advantage is that the light-weight polyurea does not require additional structural members to support the retrofit system like some ballasted systems. As in new roof applications, a final reflective topcoat containing the borosilicate spheres provides a permanently sealed, highly reflective surface for protection against ultraviolet degradation and for enhanced energy efficiency.
EERS International, Inc. of Fort Lauderdale, Florida, supplied the polyurea and the highly reflective topcoat containing the borosilicate spheres to the Edwards Air Force Base and San Diego Naval Base Marine Barracks. The reflective coating is a patented product marketed under the name CERAMICOAT. EERS International, Inc. is a partner in the Energy Star>® program. When the energy savings from application of the systems are factored into the projected life-cycle costs for installation, operation, maintenance, and repair of the systems, the roofing systems pay for themselves in as few as 3 years. The life-cycle analysis shows that the benefits of these systems include:
- class "A" roof fire protection as defined by ASTM E-108,
- highly energy-efficient roof,
- lower installation cost than other commonly used roofing systems,
- minimal maintenance costs, and
- a projected 3 to 5 year payback of investment through energy savings alone.
For more information, please contact Tom Petrie of ORNL at email@example.com or see FEMP's Buying Energy Efficient Products Web site at www.eere.energy.gov/femp/procurement/roof.html.