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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.

What operator types were added to the 2017 version of NAFS?

Changes from the 2011 to the 2017 versions of NAFS added operator types including the Folding Door (FLD) System, Limited Water Folding Door (LWFLD), Top Turn Reversible (TTR) and Tropical Awning Window Secondary Storm Product (TASSP). Also added was the ability to label a door system as tested without hardware by adding an “X” to the door designation.

The five newly added operator types are:

  1. Folding Door (FLD) system: a door system that has, at a minimum, a hinge or pivot attachment of any type between two leaves (panels) and three vertical axes about which the leaves rotate. The leaves can be folded to the interior or exterior of the opening. These systems are either top hung or bottom supported by hardware that attaches to a single track system and include, at a minimum, two pivoting/ folding leaves, a frame, and a track and roller assembly. The frame has vertical and horizontal members that are joined at the intersections that fully encompass the operating and inactive leaves in a closed position. A flush set track assembly can exist in place of a sill assembly. Additional hinged and pivoting/folding leaves and/or a single-side-hinged leaf can be included in the door system.
  2. Limited Water Folding Door (LWFLD): a Folding Door System that is limited water. Limited water is a product designation that indicates that the water penetration resistance performance was achieved by testing at a pressure less than the minimum test pressure required for the indicated Performance Class and Performance Grade (PG).
  3. Top Turn Reversible (TTR) Window: a window consisting of an operable sash hinged on each vertical side that projects outward from the plane of the frame at the bottom but then pivots to allow complete reversibility of the sash. The opening can be limited in a pre-determined position for safety or to hold the sash in position under wind load. The sash is restricted in the fully reversed position for safety during cleaning.
  4. Tropical Awning Window Secondary Storm Product (TASSP): a Secondary Storm window consisting of one or more top-hinged or pivoted sash that swing outward at the bottom edge and are operated by one control device that securely closes them at both jambs without the use of any additional manually controlled locking devices (also referred to as Jal-awning window and Jalousie window). 
  5. Door System as Tested Without Hardware (for example, DASHDX), six additions: The system is tested with the hardware excluded. This is done for systems that the hardware is sold independently of the door and therefore testing of the combination is not appropriate.