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Why Choose Steel
Buildings consume one-third of all energy and two-thirds of all electricity generated. Cool metal roofs can help reduce energy consumption by lowering cooling loads with their wide array of finishes, designs and colors. While metal roofs can be made with steel or aluminum, the majority are steel roofs.
The roof can have the greatest impact on the energy use of a building. Lightly colored, more reflective roofs can save up to 40 percent in cooling energy, as reported by the Heat Island Group of the Lawrence Berkeley National Laboratory.
Cool metal roofs are an excellent option for commercial retrofit applications because they can be efficiently installed with above-sheathing ventilation, allowing heat to dissipate through the ridge vent in hot weather while acting as an insulating layer when it is cold. Metal roofs can result in as much as a 30 percent reduction in heat gain through the roof.
Metal roofs provide the optimal foundation for photovoltaic installations since the roof can be expected to last longer than the PV system it supports.
Wall and roof solar heat recovery systems can be integrated with steel cladding and used to provide air, water or process heating needs.
Cool metal roofing is available unpainted, with thermosetting coil-applied paint finishes, or with granular-coated surfaces. This family of roofing can achieve solar reflectance of over 70 percent, meeting the EPA Energy Star Roof Products Program performance criteria.
Emissivity as high as 90 percent can be achieved for painted and granular-coated metal roofing.
Painted metal roofs retain 95 percent of their initial reflectance and emittance over time. They resist the growth of organic matter and shed dirt more readily than other materials.
Cool metal roofing can help to mitigate the Urban Heat Island Effect because of its high reflectance, which can reduce ambient air temperatures.
The steel industry has developed numerous systems that effectively eliminate or reduce thermal bridging through steel members. Systems include steel panels embedded into foam insulation, "warm wall" designs where steel is placed entirely inside the insulation layer, and cost-effective ways to use continuous foam insulation.
A higher-performing building can be constructed without necessarily adding excessive amounts of foam insulation to the exterior. Higher-efficiency water heaters or heating and cooling equipment, better windows, or more insulation elsewhere are all options to explore.
Steel framers and manufacturers are being encouraged to get involved early with the designer or building owner to ensure a good performing building that does not needlessly overburden the framing with excessive costs for energy code compliance.
Steel Framing Alliance's Thermal Design Guide
describes how to use a building simulation or performance approach to getting the most out of your design. However, this requires a change in the role of framers or steel manufacturers or suppliers on the constructed project. They must be willing to get much more involved in the upfront design of the building.
AISI Fact Sheet, "Cool Metal Roofs are Energy-Efficient and Cost-Effective"
Find out how steel can contribute to a LEED v4 project