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Metal roofs protect homes from extreme weather events with durable, attractive solutions that reduce the homeowner’s carbon footprint. According to industry data, 7 million homeowners replace their roof each year -- many are looking for new "green", energy-saving options. With a minimum recycled content of 28 percent and demonstrated ability to lower energy consumption, metal roofs are in great demand.
In the U.S., metal comprises 10% of the overall residential re-roofing market. (McGraw-Hill Construction and Analytics)
Copper has played a role in architecture for thousands of years (see: Copper in architecture). In the 3rd Century B.C., copper roof shingles were installed atop of the Loha Maha Paya Temple in Sri Lanka. And the Romans used copper as roof covering for the Pantheon in 27 B.C. Centuries later, copper and its alloys were integral in European medieval architecture. The copper roof of Hildersheim Cathedral, installed in 1280 A.D., survives to this day. And the roof at Kronborg, one of northern Europe's most important Renaissance castles that was immortalized as Elsinore Castle in Shakespeare’s Hamlet, was installed in the 1585 A.D. The copper on the tower was renovated in 2009.
New manufacturing and coating technologies have allowed metal roofs to expand into the residential roofing market.
Metal Roofs are Attractive and Versatile
•Residential metal roofs are available in a wide variety of designs, textures, styles and colors.
•Metal roofing is available in traditional vertical seam profiles or can be manufactured to resemble wood shake, slate, shingles or clay tiles.
•They can complement any type of architecture.
Metal Roofs are Durable
•Resistant to cracking, shrinking and eroding, metal is virtually a maintenance-free roofing material that lasts.
•Metal roofing systems can withstand extreme weather conditions including heavy snow loads, hail storms and wildfires.
•Many metal roofing systems feature interlocking panels, which resist and eliminate damage from high winds.
•Residential metal roofs have long-term warranties, often up to 50 years.
Metal Roofs are Energy and Cost Efficient
•Metal roofs can save homeowners up to 40% in annual energy costs, depending on geographical region.
•Residential metal roofs have a lower life cycle cost compared to other roofing materials.
•Metal roofs increase the value of a home. In fact, a metal roof adds approximately $1.45 per square foot to a home’s overall value.
•Many insurance companies give discounts of up to 35 percent to homes with metal roofs.
Metal Roofs are environmentally friendly
•Many residential metal roofs now utilize reflective pigment technology, which results in overall home energy efficiency.
•Residential metal roofs are made from 30-60% recycled material.
•Conventional roofing products contribute an estimated 20 billion pounds of waste to U.S. landfills annually, whereas metal roofs can often be installed over an existing roof, omitting the need for tear-off and disposal.
There is a myth that metal roofs are louder than other types of roofs during a rainstorm. As long as the roof is properly installed with correct underlayments, it won't be any louder than an asphalt roof. Still, this myth makes some people reject metal roofs.
=== Metal roofing in retrofit applications
Metal roofing is usually easily applied over an existing roof. In situations where reducing the cost of labor is essential, it can be helpful to have this option.
Many different types of coatings are used on metal panels: anti-rust, waterproofing, heat reflective. They are made of various materials such as epoxy, ceramic and, more recently, materials developed through nanotechnology.
Metal sheet roofs are very affordable, durable, and quick to install, which makes their use extremely popular in the construction of commercial and industrial buildings. The major problem with metal roofs in warm weather is that they absorb and retain enormous quantities of heat. In non-air-conditioned buildings, this translates directly into high building envelope heat loads, temperature and moisture build-up. In air-conditioned buildings, it means higher energy costs as the air-conditioning has to fight the heat that builds up during the day, even when the sky is overcast (ultraviolet rays, the major source of heat from solar radiation, will penetrate clouds). Because buildings with metal roofs are hotter than the things around them, they contribute to the urban heat island effect. A metal sheet roof in tropical countries, for example, can reach a temperature above 75°C / 167°F.
Ceramic coatings are the most popular heat reflective coatings applied on metal sheet roofs worldwide. The technology is several decades old and was initially developed by NASA for the American space program. Most ceramic coatings are made from regular paint, with ceramic beads mixed in as an additive. Although they reflect, on average, 75% to 85% of solar radiations, their performance tends to plummet by 30+% after a few years because of dirt build-up. Their composition and thickness (from 500 to 1,000 micrometres) can cause cracks to appear, and the color selection is very limited — mainly white with a matte finish. Because of this, their application is mostly limited to industrial and commercial buildings. However, when the cost of the investment is the main issue, they are an affordable choice for insulating metal sheet roofs.
Nanotechnology solar reflective coatings are efficient heat-reflective coatings that can be applied on roofing materials. They are radiant barriers which increase in performance exponentially with the surface's heat, making them perfect for application on metal sheet roofs. Heat load on buildings with metal sheet roofs is typically reduced by 30%, which instantly improves the building's energy-efficiency and caps heat build-up. Developers can take advantage of the affordability and wide availability of metal roofs while transforming them into a high performance heat shield. Traditional under-roof insulation such as PU foam or PE foam can provide additional insulation.
This new generation of nanotechnology coatings adds value and benefits to metal sheet roofs:
Coatings are sometimes applied to copper. Clear coatings preserve the natural color, warmth and metallic tone of copper alloys. Oils exclude moisture from copper roofs and flashings and simultaneously enhance their appearance by bringing out a rich luster and depth of color. The most popular oils are Lemon Oil, U.S.P., Lemon Grass Oil, Native E.I., paraffin oils, linseed oil, and castor oil. On copper roofing or flashing, reapplication as infrequently as once every three years can effectively retard patina formation. In arid climates, the maximum span between oilings may be extended to from three to five years. Opaque paint coatings are used primarily for work applied over copper when substrate integrity and longevity are desired but a specific color other than the naturally occurring copper hues is required. Lead-coated copper coatings are used when the appearance of exposed lead is desired or where water runoff from uncoated copper alloys would ordinarily stain lighter-colored building materials, such as marble, limestone, stucco, mortar or concrete. Zinc-tin coatings are an alternative to lead coatings since they have approximately the same appearance and workability. (For more information, see: Copper in architecture: finishes.)