Fenestration Performance Classes Translated

Fenestration standards are always evolving due to changes in technology, building codes and rating system performance requirements. The performance-based, material-neutral North American Fenestration Standard (NAFS) governing windows, doors and skylights, AAMA/WDMA/CSA 101/I.S.2/A440, is no exception. The last time performance classes were changed was between the 2005 to the 2008 version. The 2008 edition 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 simplified the specifier’s task in matching fenestration performance to project requirements and consolidate testing requirements for manufacturers.

In the 1997 and 2002 editions, there were five performance classes, described as: “R” for Residential, “LC” for Light Commercial, “C” for Commercial, “HC” for Heavy Commercial and “AW” for Architectural. The descriptions were intended to act as a general guide in helping to determine which class was best suited for a particular application. In the 2005 edition, the five performance classes remained but the descriptions were deleted, as the choice of Performance Class is made independently of the use of a building. (Note that the term “Performance Grade” is used in NAFS-08 to prevent confusion with “Performance Classes” as used in NAFS-05.) NAFS-08 provided clarification of the meaning of and difference between design pressure (DP) and performance grade (PG). This was done because some manufacturers were marketing products solely based on the design pressure (DP) rating. PG means that the product was tested to the applicable design pressure as well as all the other requirements identified by the standard/specification.

Starting with the 2008 edition of NAFS and continuing in the 2011, 2017 and 2022 editions, the C and HC performance classifications have been eliminated. A new “CW” classification has been added, which reduces the total number of performance classifications from five to four.

Note: The water penetration resistance test pressure is based on 15% of the design pressure (DP) for LC, CW, and HC performance classes and 20% of the design pressure (DP) for AW performance classes. The minimum water resistance test pressure for R-class products is 140 Pa (2.90 psf) – higher than 15% of the DP. The water resistance test pressure is capped at 580 Pa (12 psf) in the U.S and 720 Pa (15 psf) in Canada. The water penetration resistance test pressure for R products is also 15% of DP. It just starts at 2.9 psf for the DP of 15. Note also that for skylights, the structural design pressure is 200 percent of design pressure, whereas it is 150 percent for windows and doors.

For more information on changes to the 2008, 2011, 2017 and 2022 editions of NAFS performance classifications, visit the NAFS Overview web page.

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