Metal roof

Zinc, standing-seam roof in Poland

Flat-seam metal roofing was used here on the problem areas. Cauterets, France.

A metal roof is a roofing system made from metal pieces, or tiles. It is a component of the building envelope.

History

Copper has played a significant role in architecture for thousands of years (see: copper in architecture). In the 3rd century B.C., copper roof shingles were installed atop the Lovamahapaya Temple in Sri Lanka.^[1] The Romans used copper as roof covering for the Pantheon in 27 B.C.^[2] Centuries later, copper and its alloys were integral in European medieval architecture. The copper roof of St. Mary's Cathedral, Hildesheim, installed in 1280 A.D., survived until its destruction during bombings in World War II.^[3] The roof at Kronborg, one of northern Europe's most important Renaissance castles (immortalized as Elsinore Castle in Shakespeare’s Hamlet) was installed in 1585 A.D.^[4] The copper on the tower was renovated in 2009.^[5]

Advantages

• Can consist of a high percentage of recycled material and is 100% recyclable^[6]
• Does not get as hot as asphalt, reflects heat away from the home better than asphalt (reducing energy bills in the summer), which reduces the heat island effect when compared to asphalt. Coupled with its better insulating abilities, metal roofs can offer a 40% reduction in energy costs in the summer, and up to a 15% reduction in the energy costs in the winter according to a 2008 Study by Oak Ridge National Laboratory. This is based on a strapping system of four inches between the plywood and the "cool-color" metal on top. ^[7] This allows an air gap between the plywood roof and the metal. Cool-color metals are the light colors like white. The study went on to say that re-sealing and insulating air ducts in the attic will save even more money.^[8]
• Because of their longevity, most metal roofs cost less money than asphalt shingles in the long term.^[9]

Material types

• Corrugated galvanized steel. This describes the original product that was wrought iron–steel sheet coated with zinc and then roll formed into corrugated sheets.
• A blend of zinc, aluminum, and silicon-coated steel, sold under various trade names like "Zincalume", "Galvalume", etc. Sometimes left in the raw zinc finish, but more widely used as a base metal under factory-coated colors.
• Standing seam metal. This is a metal product that comes in rolled form and in various widths. The material is "seamed" together using a special seaming tool that is run vertically up the panel to seal the joints and prevent water intrusion.
• Metal tile sheets. These are usually painted or stone-coated steel.
• Stainless steel. Usually roll-formed into standing seam profiles; however, shingles are available.
• Copper. Copper roofs offer corrosion resistance, durability, long life, low maintenance, radio frequency shielding, lightning protection, and sustainability benefits. Copper roofs are often one of the most architecturally distinguishable features of prominent buildings, including churches, government buildings, and universities.^[10] Today, copper is used in roofing systems, flashings and copings, rain gutters and downspouts, domes, spires, vaults, and various other architectural design elements. At the Lyle Center for Regenerative Studies copper is used for regenerative principles of sustainable design: if the building were to be dismantled the copper could be reused because of its high value in recycling and its variety of potential uses. A vented copper roof assembly at Oak Ridge National Laboratories (U.S.) substantially reduced heat gain versus stone-coated steel shingle (SR246E90) or asphalt shingle (SR093E89), resulting in lower energy costs.^[11]
• Aluminum.
• Stone coated steel. Panels made from zinc/aluminium-coated steel with acrylic gel coating. The stones are usually a natural product with a colored ceramic coating.
• Lead
• Tin

Coating

Several different types of coatings are used on metal panels: anti-rust, waterproofing, and heat reflective. They are made of various materials such as epoxy and ceramic.

Ceramic coatings can be applied on metal roof materials to add heat reflective characteristic. Most ceramic coatings are made from regular paint, with ceramic beads mixed in as an additive.

Coatings are sometimes applied to copper.^[12][13] 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., lemongrass 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.^[14] 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.^[15] Zinc-tin coatings are an alternative to lead coatings since they have approximately the same appearance and workability.^[16][17]

See also

• Corrugated galvanised iron
• Reflective surfaces (geoengineering)
• Green building
• Metal Building Manufacturers Association
• Metal Roofing Alliance

References

1. Seale, Wayne (2007). The role of copper, brass, and bronze in architecture and design; Metal Architecture, May 2007
2. Copper roofing in detail; Copper in Architecture; Copper Development Association, U.K., www.cda.org.uk/arch
3. Copper Roofing in Detail; Copper in Architecture; Copper Development Association, U.K., www.cda.org.uk/arch
4. Kronborg completed; Agency for Palaces and Cultural Properties, København, http://www.slke.dk/en/slotteoghaver/slotte/kronborg/kronborgshistorie/kronborgfaerdigbygget.aspx?highlight=copper
5. Agency for Palaces and Cultural Properties, Renovation of the Tower of Christianborg Palace., http://www.slke.dk/en/slotteoghaver/slotte/christiansborgslot/hovedslottet/renoveringaftaarnet.aspx?highlight=copper+roof
6. http://www.cnbc.com/id/100876837
7. http://www.metalroofing.systems/top-70-metal-roofing-facts-faqs-pros-and-cons-consumer-guide/
8. Miller, William; Kośny, Jan (2008). "Next-Generation Roofs and Attics for Homes". 2008 ACEEE Summer Study on Energy Efficiency in Buildings. ISBN 0-918249-58-9.
9. http://www.bobvila.com/articles/381-metal-roofs-on-the-rise/
10. Austin, Jim (2006). Copper: The peacock of metals, Metal Roofing, April–May 2006; www.metalroofingmag.com
11. Copper roofs are cool, Architecture: Working with Copper, Copper Development Association, 2009; http://www.copper.org/publications/pub_list/pdf/a4094.pdf
12. Clear coatings on copper alloys – Technical Report; Copper Application Data, A4027; Copper Development Association
13. Clear organic finishes for copper and copper alloys; Application Data Sheet 161/0; Copper Development Association Inc.
14. Finishes – Coatings, Copper in Architecture Design Handbook, Copper Development Association Inc., http://www.copper.org/applications/architecture/arch_dhb/finishes/finishes.html#ctngs
15. Sternthal, Daniel (2000). Copper flashings in contemporary construction, The Construction Specifier, Magazine of the Construction Specifications Institute, October 2000
16. The glory of copper; Metal Roofing Magazine, December 2002/January 2003
17. Sternthal, Daniel 2000. Copper flashings in contemporary construction, The Construction Specifier, Magazine of the Construction Specifications Institute, October 2000