NOW Opinion on Aluminum Sheet vs. Aluminum Composite
Updated: April 11, 2012
Frequently owners, specifiers, and building contractors ask our personnel for recommendations regarding aluminum composite material and aluminum sheet. NOW Specialties engineers, markets, and fabricates systems for both and is uniquely qualified to comment on the similarities and differences between the two products.
The discussion should begin with definitions: aluminum composite material (ACM) is a thermoplastic core, chemically-bonded to two prefinished aluminum sheets, usually 0.02” thick (equivalent to 25-gauge). The exterior sheet is coil-coated with a high-performance PVDF coat, normally warranted for 30 years, in compliance with ASTM D-4214 (chalk resistance) and with ASTM D-2244 (fade resistance). The interior sheet is finished with a siliconized polyester paint in a random color, unless specified otherwise.
Aluminum sheet is a solid material and an almost entirely pure element. When properly used in architectural applications, it is cut into sheets, fabricated and formed, then post-finished. The exterior side is finished in a spray-applied PVDF coat, normally warranted for 10 or 20 years, in compliance with ASTM D-4214 (chalk resistance). Warranties have been known to altogether omit ASTM D-2244 (fade resistance) or allow application tolerances of ∆2, per D-2244. AAMA 2605-05 even states that “exact color uniformity should not be expected” when using “pearlescent mica or metallic” finishes. Reiterating this point in the interest of clarity, the material is delivered and installed exhibiting ∆2 color differences, and color fade begins afterward, exempt from any warranty obligation. The interior side of aluminum sheet is finished with primer, unless otherwise specified.
ACM does have some inherent disadvantages: sheet widths are limited to 62”; the material cannot be welded; it is not meant to be used in roll-forming or break-metal applications; and producing small quantities of custom colors can be cost prohibitive. In contrast, the heavier aluminum gauges of aluminum sheet can be welded, and the lighter sheet/coil gauges can be used in roll-forming and break-metal applications. Aluminum sheet also allows for more affordable custom color selection since no post-applied color is significantly more or less expensive than any other color. Aluminum sheet is, however, limited in maximum width and is much more prone to visible oil-canning, despite its increased material cost.
One perceived but unfounded disadvantage of ACM is that the routed corners reduce the material to a single, exterior sheet, with an approximately 25-gauge thickness. (See our 1100 system details for a graphic depiction of this.) Designers often require reinforced corners with a shop-adhered aluminum angle on the back side of the routed corner. ACM fabricators can accommodate this requirement with very little cost. Indeed, many installation systems already incorporate this reinforcement into the extrusion profiles. Again, see our 1100 system details for more information.
For welded panels, small quantities of custom colors, roll-formed profiles, and break-metal flashing, NOW Specialties recommends aluminum sheet or coil. For almost all other architectural applications, we recommend aluminum composite material, which is flatter, more affordable, more design-flexible, and superior in paint finish and color consistency.
For further information, or to comment on this position, please contact Collin Sutt: 972-416-7065 (firstname.lastname@example.org).