You have chosen Alucobond for the endless design possibilities that this superior cladding product affords. Now, serious consideration must be given to functionality in terms of how the Alucobond will be attached to the building. Generally speaking, Alucobond is installed in one of three ways: Route and Return Wet Seal, Route and Return Dry Seal, and Rain Screen. While all three of these attachment methods perform very well when engineered, fabricated, and installed properly, there are situations in which one may be more appropriate than another. When choosing an attachment method a designer must consider budget, aesthetics, maintenance, and perhaps most importantly, how the Alucobond will be incorporated and function within the overall wall assembly.
The methods by which Alucobond has been installed over the last 35 years have evolved. Originally the accepted method embraced the concept of building a wall in which the Alucobond façade acts as the primary weather barrier by caulking all the joints between panels. Today, highly engineered systems function in such a way that manage any moisture that infiltrates the wall cavity and also allows for continuous exterior insulation that drastically improves the thermal efficiency of the building.
Starting at the beginning of this evolution we’ll take a closer look at the Route and Return Wet Seal System. This method (while not always the case) is typically considered to be the most economical way to install Alucobond. It relies on a primary silicone sealant between each panel for an air and water barrier. The system utilizes basic male / female clips to attach the material to the building and can accommodate anything from the simple to the very complex panel designs.
This attachment method also presents a number of challenges. Cleanliness can become an issue if the building owner isn’t diligent about maintaining the façade. This is due to the fact that silicone caulk attracts dirt. This dirt over time, and between rain cycles, weeps from the caulk joints and down the face of the panel. If left unattended this will cause the caulk joints and panels to look extremely dirty within a short period. Inevitably, the silicone sealant between the panels will have to be replaced. Perhaps the most destructive potential problem with the Route and Return Wet Seal is its’ limitation to manage moisture.
Because the caulk joint is the primary weather barrier, it is critical that the sealant is perfectly installed without as much as a pinhole within the bead. As we know, because “perfect” is seldom obtained in construction and pinholes can occur in a bead of caulk from time to time, under wind-load negative pressure is created within the wall cavity which often sucks moisture into the system. Once inside, there is no way for this moisture to escape thus creating a black mold situation. Lastly, due to the fact that this system is the least sophisticated, the pool of contractors fabricating and installing composite aluminum panels in this way is quite large. While this can be a good thing in the interest of competitive bidding, it also opens the project up to contractors that may not have the same level of expertise as those who work with the more highly engineered attachment methods potentially further exasperating some of the issues discussed above.
As Alucobond became a more popular façade solution, people started to identify some of the shortfalls of the Route and Return Wet Seal attachment method and began to develop systems to address these issues. The Route and Return Dry system functions similarly to the Wet Seal but gaskets are incorporated into the joints between panels in lieu of the silicone sealant. This allows the façade to stay much cleaner over time, in fact, rainfall typically is sufficient to keep the façade looking tidy.
Further, this system introduced continuous extrusions around each panel to maintain structural integrity and a secondary gutter system helps to insure water-tight performance. While these advancements addressed many of the shortcomings of the Wet Seal System, they did not come without a price as the Route and Return Dry Seal is typically 25-30% more expensive than the other attachment methods (including the Rain Screen to be discussed later.) This can be attributed to a couple of issues: (1) the amount of aluminum required for the continuous extrusion hardware / secondary gutter, and (2) installation time tends to be increased due to the critical importance of seating each panel correctly to allow for the gasket to achieve the necessary water-tight seal. While this system is still considered to be an accepted way to install Alucobond, budgetary concerns and the reliance on a gasket as the primary weather barrier typically render this method as the least utilized attachment method of the three.
Today, variations of the Route and Return Rain Screen System are by far the most popular methods for installing Alucobond. Reputable fabricators have subjected their rain screen solutions to rigorous air and water tests and an increasing number have also participated in fire testing. The fact that these contractors have taken it upon themselves to test their systems in accordance with strict building code requirements (and are willing to provide architects and designers with the results) has prevented many substandard fabricators from even participating in rain screen construction. Specifying a Route and Return Rain Screen increases the likelihood that the complete wall assembly, not only the Alucobond component, will function as designed and required by code. These highly engineered and tested systems have now addressed all of the deficiencies of the past.
Architects can choose between a rain screen with inboard or outboard insulation. Increasingly designers of wall assemblies are moving the insulation to the outboard side of the wall. This allows for a continuous layer of insulation free from the normal penetrations required by typical inboard insulation construction. When a wall assembly is constructed in this way, with the proper thermally broken attachment clips, and in compliance with ASHRAE 90.1, there is a significant benefit to the thermal efficiency of the building’s HVAC system. While outboard insulation wall assemblies typically cost more (+/-20%) than inboard insulation, the ROI on HVAC costs is at least that much and often continues in perpetuity.
Aesthetically, a concealed membrane is used over the substrate as the primary air and water barrier. This allows the joints between panels to remain open. Water is managed through a gutter system and open joint ventilation allows the wall to breathe, eliminating the negative pressure and black mold concern. The system is extremely low maintenance due to the absence of caulk. In addition, options are now available to the designer in terms of reveal size and color.
The Route and Return Rain Screen is much easier to install given the fact that moisture maintenance now happens behind the Alucobond material and less time and effort is spent preventing air and water infiltration at the panel joints. Because rain screen construction has become the standard within the industry, it has significantly driven the price down to the point that, what was once considered the most expensive way to install Alucobond, many times now can be the most economical method. Given all the benefits of the Rout and Return Rain Screen System and the fact that it remains an economical solution, one must ask “why would any other system be used?”
In conclusion, it’s important to reiterate that under perfect conditions all three of the typical attachment methods perform very well. As with any construction methodology, advancements are made over time to develop better practices and products to satisfy evolving building codes, help decrease the likelihood of human error, and increase the building’s overall longevity. Rain Screen construction is the culmination of many years of study and practical experience and clearly appears to be the future of Alucobond design, fabrication, and installation.