There seems to be a large misunderstanding in the architectural community of what represents a pressure equalized rain screen system (PER), particularly when specifying wall panel systems. Far too often the pressure equalized rain screen system, or AAMA 508-07, “Voluntary Test Method and Specification for Pressure Equalized Rain Screen Wall Cladding Systems”, is referenced, however the AAMA 509-09, “Voluntary Test and Classification Method of Drained and Back Ventilated Rain Screen Wall Cladding Systems is presented in the specification details, which leads to confusion.
The significant difference between these two types of wall cladding systems, hinges on the amount of water and moisture that the panel system will allow through it, which then reaches the sub-wall or built out wall assembly behind it. More often than not, rain screen systems are improperly specified, as the manufacturers and suppliers of the drained/back-ventilated wall panel systems will often market their systems as being designed after the AAMA 508-07 systems. This is usually done to allow them more leverage in getting specified and increasing the odds of being used on key building projects. How is this allowed to happen though? How do I tell them apart?
The key difference is as simple as this. In order to comply with an AAMA 508-07 pressure equalized rain screen system test, a wall assembly specimen that has been sealed around the edges of a test rig must have vacuum drawn at 15 KPa on the system for 15 minutes, and no more than 5% moisture or wetting can be measured on the sub wall, during or after the test. This is very different than when an AAMA 509-09 system is tested, because it is an open joint system and no vacuum can possibly be drawn on it. The 509-09 system being a drained/back-ventilated open joint wall panel system should never be mistaken for an AAMA 508-07 (PER) system. It is important to remember that AAMA 509-09 test protocol is a classification method and not a pass/ fail test. Hence (DBV) systems will likely allow much more water to enter the wall cavity than a (PER) system. It is important for the designer and detailer to understand the volume of water that must be managed and drained from the (DBV) systems via the AAMA 509-09 test, and as a result that the proper moisture barriers are utilized to keep the building dry.
While reviewing specifications for our customers upcoming projects and when receiving inquiries from architectural firms, on our designed and tested panel systems, we inevitably have the discussion with them to clarify which building envelope, 508 or 509, is being considered and why. Most Fabricators who perform Division 07 scope of work are finding themselves becoming more and more frustrated when it comes to attempting to comply with specifications these days. It seems some Architects and Spec writers are still not comprehending the key differences between the two systems. Naturally, this can lead to poorly performing wall assemblies and problematic structures, resulting in compromised building envelopes, excessive water infiltration, mould, mildew and other health related problems.
Architects and Spec writers should also know that regardless of whether a system is specified as AAMA 508-07 or AAMA 509-09, neither of these systems are water tight or should be referred to as a `wet joint system’. If you happen to come across a wet joint spec that calls for a AAMA 508 or 509 system, then you should begin to look for clarification from the Architect on what he is looking to accomplish with his design. This is because wet joint (caulk joint) systems have the panel joints or reveals filled with backer rod and caulking right to the face of the panel, leaving no openings for weep holes or potential pressure equalization to take place. These errors found in specs are often the result of cut-and-paste procedures when changes are being made to designs. Perhaps a decision has been made to use another product in lieu of aluminum plate or aluminum composite panels, and the assumption made is that the alternate product will perform the same and provide a pressure equalized rain screen façade, when it is often found not to be the case. The result of this lack of diligence is often a poorly designed/performing facade.
The unfortunate but all too often downside to the misunderstanding and miss-application between the pressure equalized rain screen system and the drain/back-ventilated system, can result in a compromised wall assembly. There are countless examples throughout North America, where a AAMA 509-09 facade was constructed, while the principles of the AAMA 508-07 pressure equalized rain screen systems were thought to have been followed. The consequences of this inaccurate application are structures now laden with mould, mildew and various other health concerns. Unfortunately, the costs associated with these damages and the repair work to these failed facades can range from hundreds of thousands of dollars, to a complete tear down and rebuild.
The lack of education on the differences between AMMA 508-07 and AAMA 509-09 systems often leads to owners incurring additional and unnecessary costs. With value engineering being such a focal point these days, designers and owners are willing to consider almost any alternate product to meet budgets, and in doing so neglect to consider whether their wall assembly will perform the same. Perhaps smarter designs using fewer building materials and faster installation procedures should be considered, especially if system performance and quality can me maintained while having a positive impact on budget. EVOMAXci? EVOMAXci is a new wall assembly system comprised of components including sub-wall, rigid insulation, z-bars, EVO™ ACM.After all, if an owner can save 10 to 20% in construction costs and utilize a superior integrated system for a wall assembly, using a specified tested (PER) system, wouldn’t they want to know this?
Make sure you understand the differences between AAMA 508-07 and AAMA 509-09 before you begin the design-build process, so that you can avoid costly mistakes or repairs down the road. Too often we see composite specs come out that say pressure equalized rain screen system, then call for a AAMA 509-09 system.
Time for a phone call!
Do your due diligence and research so you understand the difference between these two systems, their applications and uses.
Be aware, be knowledgeable and clarify, for your own sake.