Volume 8, Issue 3 - March 2007

WDMA Opens Up

Choosing the Best Prescription
Comparing Performance-Based Standards vs. Prescriptive Engineering
by Joel Hoiland

What’s the true value of performance-based standards rather than prescriptive engineering? Performance standards encourage greater industry innovation and higher customer satisfaction through a premier quality product. 

Standards need to be dynamic documents that meet industry needs. How a door, window or skylight operates in the field is the most important criteria and we continue to develop standards based on the performance needs of all constituents, rather than focus on specific materials and components.

The value of performance-based engineering is clear. This method encourages the use of both new and proven technologies and processes, not material exclusivity. By focusing on performance, consumers are assured of the latest materials that are the most efficient, cost effective and relevant to the installation or the environment of the project. 

Prescriptive or Performance
The wording and requirements of a standard determines how it will be applied by the user. Standards are created for a specific purpose and in such a manner so as not to be misinterpreted easily. And in reality, standards may contain both prescriptive as well as performance criteria. 

A prescriptive standard is one that contains wording that specifically describes the “ways and means” of attaining the end results. Prescriptive standards usually do not state what is to be attained, but simply specify how it is to be attained. They usually include minimums or limitations on certain elements of the process being described and specify precise dimensions, quantities or materials that must be used. Following prescriptive standards allows manufacturers to skip the diligence and engineering calculations for design. The downside to a prescriptive design method is that it is restrictive, limits innovation and creativity and tends to “over-design” to make the design a “one-size-fits-all” solution.

A performance standard contains wording that specifically describes the end-result to be attained and the tests to be performed to provide that result, without stating the methods for achieving its requirements. This type of standard is worded to describe how the design, method or specification is to perform when completed. Following performance standards requires an understanding of how materials, components and assemblies interact. The upside to a performance design method is that innovation and creativity are incorporated in design easily and products take advantage of their full capability.

Standards Take Charge
The release of 101/I.S.2/A440-05, Standard/Specification for Windows, Doors and Unit Skylights was pivotal to WDMA’s goal to continue to offer and promote performance-based standards. 

WDMA worked diligently to develop this specification for doors, windows and unit skylights to reflect current, real-world performance standards. Now, work continues on the next revision of this standard to further remove needless prescriptive language and add market-driven performance characteristics. WDMA has released a major revision to interior architectural doors called the Industry Specification for Architectural Wood Flush Doors or I.S. 1A. Focusing on distinct performance levels and application-driven specifications, I.S.1A joined 101/I.S.2/A440-05 to provide the industry with a well-rounded compendium of standards that aids the construction community. In addition, I.S. 6A-01, Industry Standard for Architectural Stile and Rail Doors, currently in a draft review stage, also will focus on performance characteristics wherever applicable. 

The marketplace expects and deserves quality products. WDMA is positioning itself as the technical leader in performance standards and as a representative of the diverse materials used to manufacture doors, windows and skylights. This paves the way for WDMA members to make products that can be installed with confidence and long-lasting results. 

Joel Hoiland is the president of the Window and Door Manufacturers Association based in Des Plaines, Ill. He may be reached at jhoiland@wdma.com.


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