What About Galvanized?
Even when painted, galvanized steel flashing and mounts can be expected to last only about 15 years according to the Sheet Metal and Air Conditioning National Association's (SMACNA) Architectural Sheet Metal Manual. A primary reason that Quick Mount PV’s flashed mounts last much longer than galvanized steel products is due to the fact that our products are constructed with corrosion resistant aluminum and all exposed hardware is stainless steel. This combination of materials provides an estimated life of 50 years. The SMACNA manual allows for, at minimum, 24-gauge galvanized steel but stipulates that the flashing must be painted as well.
PV modules are expected to provide power for 20-30 years, and in some areas even longer. For this reason, it is usually a good idea to install new shingles or tile underlayment prior to solar installation so that you won’t have to reroof down the road. For this same reason, using a flashed mounting system that lasts as long as the PV modules makes the most sense.
SMACNA's manual lists the pros and cons of a range of flashing materials, including stainless steel, copper, lead, aluminum, and galvanized steel. Stainless is considered 100-year compatible, but is very expensive and relatively difficult to fabricate in the field. Copper and lead will last nearly as long and are easy to field fabricate, but they are expensive, and lead is toxic to work with on a regular basis. Aluminum is considered 50-year compatible, is much less costly and non-toxic, but is still not as easy to field fabricate as galvanized steel, copper and lead. Because Quick Mount PV flashings are fabricated to the right size, there’s no need for any metal cutting on the roof.
Galvanized steel flashings are inexpensive, readily available, and easy to fabricate at the job site. However, many roofing manufacturers’ instructions warn that using galvanized flashings may void their warranty altogether. If you must use galvanized steel flashings, be sure to carefully read the roof warranty. Some warranties may accept galvanized flashing of 24 gauge while at the same time rejecting slightly thinner 26 gauge.
One more note on the use of galvanized steel: The Unified Facilities Guide Specifications for USACE (US Army Corps of Engineers), NAVFAC (Naval Facilities Engineering Command), AFCESA (Air Force Civil Engineer Support Agency), and NASA (National Aeronautics and Space Administration), forbid the use of galvanized flashings, as they do not have the life expectancy required to last as long as their roofs.
For more details, visit: www.smacna.org
