A metal roof is a roofing system made from metal pieces or tiles characterized by its high resistance, impermeability and longevity. It is a component of the building envelope. Zinc, copper and steel alloys are commonly used.
Metal roofs can last up to 100 years, with installers providing 50 year warranties. Because of their longevity, most metal roofs are less expensive than asphalt shingles in the long term.
Metal roofing can consist of a high percentage of recycled material and is 100% recyclable. It does not get as hot as asphalt, a common roofing material, and it reflects heat away from the building underneath in summertime. On a larger scale, its use reduces the heat island effect of cities when compared to asphalt. Coupled with its better insulating abilities, metal roofs can offer not only a 40% reduction in energy costs in the summer, but also up to a 15% reduction in the energy costs in the winter according to a 2008 Study by Oak Ridge National Laboratory. This finding is based on the use of a strapping system of four inches between the plywood and "cool-color" metal on top, which provides an air gap between the plywood roof and the metal. Cool-color metals are light, reflective colors, like white. The study went on to say that re-sealing and insulating air ducts in the attic will save even more money.
Metal roofing is also lightweight, creates little stress on the load bearing roof support structures and can be installed on top of an existing roof. A lightweight roof is very useful for large and or old structures, as it helps to maintain the overall structural integrity of the building. Despite its light weight, metal roofing provides increased wind resistance when compared to other roofing materials. This is because metal roofing systems use interlocking panels.