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North American Fenestration Standard Frequently Asked Questions

What is Performance Grade?

Performance Grade is a numeric designator that defines a specific set of NAFS-specified product performance requirements for a specific Design Pressure (DP) range as required by conditions at the intended location of the building. A product achieves a Performance Grade rating only upon successful completion of all applicable tests–primarily those for structural performance under wind loading and for resistance to water penetration and air leakage.

What do the Performance Classes included in NAFS represent?

Changes in the 2008 version of NAFS realigned and reduced the total number of the Performance Class designations as defined by the Performance Grade (a set of performance requirements corresponding to a Design Pressure range) at the intended location of the building. This simplifies the specifier’s task in matching fenestration performance to project requirements and consolidates testing requirements for manufacturers.

In the 1997, 2002 and 2005 editions, there were five Performance Classes - R, LC, C, HC and AW. For the 2008, the C and HC performance classifications were eliminated and replaced with a singular CW classification. There have been no further changes to the performance classifications since 2008, which are currently defined as:

  • R: commonly used in one- and two-family dwellings
  • LC: commonly used in low-rise and mid-rise multi-family dwellings and other buildings where larger sizes and higher loading requirements are expected
  • CW: commonly used in low-rise and mid-rise buildings where larger sizes, higher loading requirements, limits on deflection and heavy use are expected
  • AW: commonly used in high-rise and mid-rise buildings to meet increased loading requirements and limits on deflection, and in buildings where frequent and extreme use of the fenestration products is expected

For more information, visit the Performance Class Overview web page.