Why is it important to use a panel mounting system that allows for expansion and contraction of Aluminum Composite Material?
Aluminum Composite material (ACM) consists of two skins of aluminum, typically 0.020″ thick each, sandwiching a core material. ACM is routed from the back to create a V-Groove, leaving a little bit of the core material on the back side of the front skin. This routed panel can then be folded easily by hand along the groove.
The remaining aluminum face skin is now what holds the panel in place for years to come. As with any building product, there is a certain “coefficient of linear expansion”, meaning that as temperature changes, the material will shrink (when it cools) or expand (when it warms up).
In a typical “rout and return” system panels are v-grooved and folded to make “returns” around the perimeter and Panel Extrusions are fastened to these returns. These fabricated panels, sometimes called cassettes, are then fastened to the building using a variety of methods, either with wall extrusions, mounting clips, etc… Many times however, these panels are mounted to the substrate without allowance for thermal expansion, often pushed tight one against the other.
When there is no allowance for thermal expansion the panels may begin to show “wrinkles” or “waffling” on the panels exposed surfaces, often called the “oil can” (pictured) effect and must be avoided. Thermal expansion may also cause bending at the weakest parts of the panel which is at the folds of the returns.
This means expansion and contraction will in effect be opening and closing the fold repeatedly, although it is a very small amount, potentially weakening the fold or allowing for uncontrolled water penetration.
What happens when you repeatedly bend Metal? Finally it breaks! Unfortunately this is one feature that many façade designers and consultants overlook when specifying an ACM Rainscreen System.
There are a lot of factors involved that increase or decrease the likelihood of there being a problem with thermal expansion. One is the color of the ACM. Another is temperature ranges. Some regions have very small temperature ranges all year long and other have radical changes not only from day to day but from season to season as well.
The Fairview Arrowhead Panel Installation System (pictured) has been designed, engineered and tested to safely allow for thermal expansion and contraction.