Performance Class Overview
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 latest change from the 2005 to the 2008 version (now referenced in current International Building Codes and available as the basis for third-party testing and certification) have 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 will simplify 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-2008 to prevent confusion with “Performance Classes” as used in NAFS-2005.) 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.
For the 2008 edition of NAFS, 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. Entry-level (“gateway”) Performance Grades are:
- 15 psf (720 Pa) for R class (commonly used in one- and two-family dwellings)
- 25 psf (1200 Pa) for LC class (commonly used for low- and mid-rise multifamily dwellings and other buildings where larger sizes and higher loading requirements are expected)
- 30 psf (1,440 Pa) for the new CW class (commonly used in low- and mid-rise buildings where larger sizes, higher loading requirements, limits on deflection and heavier use are expected)
- 40 psf (1,920 Pa) for the AW class (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)
Optional performance grades may be specified in each class (except AW) above the minimum gateway requirement in increments of 240 Pa (5 psf), up to a maximum cap of 4,800 Pa (100 psf). This is higher than the caps specified in NAFS-05 for Classes R through HC– where the performance classes were capped at 2,880 Pa (60 psf) above the minimum gateway design pressure. There is no maximum Performance Grade for AW products.
The table below compares the basic parameters for Performance Classes as listed in NAFS-05 and NAFS-08 as related to the Performance Grade.
Note also that the format of the “primary designator” – the way in which compliant windows are identified – has also changed. Formerly consisting of the type code, followed by the class and performance grade (design pressure) – e.g. C-R25 for a casement product tested for R-class qualification at a design pressure of 25 psf – the designator now consists of the performance class followed by the “PG” designation and the size tested, and then the type code (e.g., class R-PG25; size tested 760 X 1520 mm (30 x 60 in) – product type C).
To qualify for a given performance grade (PG), a representative specimen of the product must pass all required performance tests for the following, in addition to all required auxiliary (durability) tests for the applicable product type and desired performance class:
a) Operating force (if applicable)
b) Air leakage resistance
c) Water penetration resistance
d) Uniform load deflection test
e) Uniform load structural test
f) Forced-entry resistance (if applicable)
*Skylight Performance Classes. Per NAFS-08, unit skylights are specified as either R or CW class [R, C or HC under NAFS-05] with the minimum Performance Grades shown. Optional Performance Grades within these classes for unit skylights are the same as those for windows and doors. AW and LC classifications are not available for unit skylights.
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 gateway 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 Gateway 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 and 2011 editions of NAFS performance classifications, visit the NAFS Overview web page.
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