Always an Open Door
by John Lewis
At the American Architectural Manufacturers Association (AAMA) we understand that industry standards can only be considered as such if the industry agrees. Thatís why a consensus-based approach has been in place for many years in the standards development process. All drafts must be reviewed by all bonafide stakeholders and their concerns must be addressed.
Letís take an example, such as the recent updating of a six-year-old standard into the recently published AAMA 450-06, Voluntary Performance Rating Method for Mulled Fenestration Assemblies. This defines how to determine the air leakage resistance, water penetration resistance and structural performance of two or more individual window products installed in a single rough opening using joining members, or mullions.
The original document, AAMA 450-00, was first developed through AAMA back in 2000. It allowed the mullion assembly to be given a rating, which could then be considered along with the ratings of the individual units in determining a rating for the entire unit configuration. The document was referenced as the foundation for mullion performance of factory-mulled combination units in AAMA/WDMA/CSA 101/I.S. 2/A440-05 and has formed the basis for optional certification of mulled assemblies under the AAMA Certification Program (resulting in a label tab indicating compliance).
The performance of mulled assemblies first gained higher-profile attention among building professionals and manufacturers in studies analyzing the damage during the 2004 and 2005 seasons. Some researchers lamented the fact that mulls in combination assemblies had not been built or tested to meet a standard and often showed disappointing performance, such as excessive water leakage.
AAMA 450-00 first defined procedures for determining the performance of mulled assemblies four years prior to these hurricane damage studies. The method essentially assigns a design pressure rating to the mulled assembly, which in turn establishes the structural and water leakage test pressures for the assembly. The design pressure is defined as the lower of that for either the individual mulled products or for the full combination assembly, as determined by either testing the total assembly, testing the mullion elements as individual components, or by calculation. Analysis based on any of these three options can then be used to determine the performance of mulls in different combination assemblies and sizes.
The standard also defines the framing material physical properties, load distribution, attachment to the rough opening and sealant considerations for grouping of mulled assemblies (so as to economically qualify more than one configuration by a single test) and sets forth appropriate ASTM test methods for determining the different performance factors.
In 2004, AAMA took a fresh look at the 2000 edition with input from the Window and Door Manufacturers Association (WDMA) in the form of 13 suggested revisions. While most of these suggestions were editorial in nature, a few were substantive and received due consideration by the Joint Task Group. Ultimately, about half of the suggestions were judged as having merit through the consensus process and were adoptedĖthe most substantive addressed the size of the tested mulled assembly.
The result of this collaboration: the AAMA 450-06 update was published earlier this year. The process worked as intended once again; the task group meeting attendees represented suppliers, testing laboratories and a minimum of ten window manufacturers, representing all framing materials.
Participation in the ongoing standards development process must be unifying, not divisive. We must work around the common focal point of customer satisfaction to bring our various factions together for the greater good of satisfied customers. Our audiences want and need credible, professional guidance. They deserve nothing less.
John Lewis serves as technical director for the American Architectural Manufacturers Association in Schaumburg, Ill. He can be reached at
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