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FREQUENTLY ASKED QUESTIONS ABOUT METAL ROOFING |
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Can a metal roof be considered a cool roof? |
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Metal roofing is a family of products that are comprised of unpainted metal and prepainted organic-coated metal. Research at the Oak Ridge National Laboratory shows the long-term performance of metal roofing with regard to solar reflectance and infrared emittance. Initial results show superior performance over other forms of construction for light-colored painted panels. Metal roofing products also stay clean over time, and do not pick up dirt, debris and other pollutants that could cause the high reflectance to degrade over time. Metal roofs retain 95% of their initial solar reflectance over time. Many competitive roofing products show significant degradation of their initial reflectance from dirt and biological growth. Metal roofing products are listed in the EPA Energy Star Roof Products Program. Their thermal properties often meet “cool roofing” criteria for rebates, credits and incentives. |
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Doesn’t metal roofing have low emissivity? |
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Unpainted metal has a relatively low emissivity, whereas a pre-painted metal roof typically has exceptionally high emissivity values. In many climates, though, infrared emittance is not a significant contributor to the overall roof performance. For example, in northern cool climates, low infrared emissivity can actually be desirable because a roof with lower emissivity holds in the building heat, which is better for thermal performance. In this type of situation, unpainted Galvalume sheet, with its high reflectivity and low emissivity, would be beneficial to overall energy savings. It is well proven that high emissivity in southern warmer climates plays a significant role in thermal performance. Here, painted and granular coated metal roofs can perform very well. |
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Is metal roofing noisy? |
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When installed with solid sheathing, a metal roof on a building will silence noise from rain, hail and bad weather as well as, if not better than any other roofing material. |
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How will a metal roof stand up to extreme weather? |
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A metal roof can withstand decades of abuse from extreme weather like high winds, heavy snow, hailstorms, and even wildfires. Metal roofing is available with a 120-mph wind rating, meaning it can withstand wind gusts of up to 120 miles per hour, equal to an F2 tornado. In cold and snowy climates, metal roofing has been the choice of building owners for years. It sheds snow fast, which protects the structural integrity of the roof, and it eliminates ice damming at the eaves. In areas that are prone to wildfires, metal roofing can protect your building when burning embers land on the roof. |
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Is a metal roof environmentally responsible? |
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Metal roofing is a sustainable building material. The high recycled content of metal roofing is far superior to asphalt-based products. According to the National Association of Homebuilders Research Center, 20 billion pounds of asphalt shingles are dumped into U.S. landfills every year. In many cases, a metal roof can often be installed over the current roof, without tearing off what's already there. This helps to reduce this excessive shingle landfill waste. |
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Is metal roofing recyclable? |
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Metal roofing is 100% recyclable if it is ever removed as part of a building renovation. Other roofing materials are often disposed of by the ton in landfills. The LEED program recognizes the importance of recyclability. Most metal roofs have recycled content from 25-95%. |
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Doesn’t condensation become a problem with metal roofs? |
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Metal roof systems can perform as well as conventional building construction. Adding a standing seam roof to a building re-roof project would allow the addition of extra insulation to provide a higher overall energy efficiency. Metal building systems and roofing systems can comply with the most recent ASHRAE 90.1 Energy Standard, which is quickly being adopted across the country and is recognized as a strict energy standard. |
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Aren’t metal roofs heavy? |
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Metal roofing can have a weight that is one third to as little as one eighth that of conventional roofing shingles. Lower weight means less load on the structure, and it can allow for metal roofing to be installed directly over old roofing material. |
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Won’t metal roofs rust? |
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Today’s metal roofing systems are made of corrosion resistant coated steel products. Aluminum-zinc alloy coatings are used to provide excellent corrosion resistance to steel roofing. High performance oven-baked paint systems are commonly used on metal roofing to provide aesthetic appeal. The paint systems provide premium color stability over decades and protect the metal substrate from the weather. Even in the unpainted condition, Galvalume coated steel roofs have been documented to provide useful life through 30 years. Based on the minimal coating loss measured, these metal roofs have been estimated to last more than 50 years before first maintenance. |
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What are the disadvantages of non-metal roofing systems compared to pre-painted metal roofing? |
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The success of cool roofs relies on maintaining the reflectivity of the roofing system. Energy savings are not necessarily constant over the lifetime of the roof system, as the solar reflectivity of a roof surface changes. Color changes caused by aging, dust, air-borne pollutants, water ponding, and the effects of biological attack can all reduce the performance of non-metal Cool Roofing (e.g. EPDM, sprayed-on coatings). High levels of maintenance and/or cleaning are critical to maintaining a highly reflective, cool surface for non-metal roofing systems. In contrast, unpainted and pre-painted metal roofing systems shed dirt and do not have problems with biological attack. Unpainted and pre-painted metal roofs are able to maintain their reflectivity over longer periods of time with minimal maintenance. In addition, metal roofing has a significant recycled content, is recyclable, sustainable, and has a much longer life span compared to most non-metal roofing systems. |
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