The Metal Construction Association (MCA) has released new research findings that conclude that certain metal roof systems can last at least 60 years, meaning they do not require replacement during a commercial building's service life. Most non-metal roofing systems require one or more full replacements within a typical building's 60-year service life, which is costly and often adds to the solid waste stream in landfills.
The study, sponsored by MCA and the ZAC Association, was conducted with oversight of three independent consulting firms which analyzed low-slope, unpainted 55 percent Al-Zn coated steel standing seam roofing, in a wide range of environments across the US
This type of roof material is known by many trade names throughout the world, principally GALVALUME® and Zincalume® in the United States. It is very common on low rise commercial buildings such as warehouses, schools, distribution centers, shopping centers, exposition halls and other facilities. Experts estimate that the market size for this type of low slope roofing in the US is over 350 million square feet.
The research team selected 14 building sites in 5 climate regions of various geographies in the continental United States, exhibiting a spectrum of climates related to heat and humidity including Hot-Dry, Hot-Humid, Cold-Dry, Cold-Humid, and Moderate-Acid. The precipitation acidity also varies considerably from one site to the next over this broad geography.
The research study concluded that the expected service life of an unpainted 55 percent Al-Zn coated steel standing seam roof constructed today in a wide range of environments using best practices can be expected to be in excess of 60 years, a value that equals the assumed building service life as described in the USGBC's Leadership in Energy and Environmental Design building rating program, version 4.
In the study, the steel panel roofs experienced corrosion rates that conservatively project service lives well beyond the service life of most buildings. The range depends on the climate and the local precipitation pH.
The study also confirmed that these types of metal roofs resist corrosion even in "weak" spots, such as sheared edges and panel profile bends. Inspections showed an absence of significant red rust after up to 35 years, indicating exceptional corrosion resistance in areas susceptible to exhibiting the first signs of corrosion.