In demanding environments where long-term high performance and durability are desired, CW and AW Class rated products should be specified and installed. The industry standard - AAMA/WDMA/CSA 101/I.S.2/A440 (NAFS – "North American Fenestration Standard / Specification for windows, doors, and skylights") defines the minimum performance and testing requirements for four classes of fenestration products. The Performance Classes are designated R, LC, CW and AW.

A general summary from NAFS 2022 notes the following:

“The Performance Class ratings should be regarded as an indication of the level of performance, with the least stringent requirements established for the R Performance Class and the most stringent for the AW Performance Class. The following descriptions can be used as a general guide in helping to determine which class is likely best suited for a particular application:

• 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.”

Each product type has a defined “gateway” set of primary requirements for the applicable product type. These gateway performance requirements are the minimum allowable performance levels for that specific performance class. There are also gateway or minimum test sizes for width and height for each performance class and product type. It is not unusual for product to be designed and tested to higher requirements. 

Typically, the minimum performance levels and the gateway size change as the Performance Class changes. All gateway test specimens achieve certain minimum Performance Grades (PG) with corresponding performance levels for air leakage resistance, water penetration resistance, uniform load resistance and, where required, forced-entry resistance and operating force. AW and CW products also have a maximum deflection limit of L/175 (where L is the length of the unsupported span) under the uniform load deflection tests. L/175 is also a requirement of complying with ASTM E1300 “Standard Practice for Determining Load Resistance of Glass in Buildings." AW products also require that permanent set not exceed 0.2 percent of the mullion span when tested to 150 percent of the design pressure while CW allows 0.3 percent and R and LC are less stringent at 0.4 percent.

All gateway test specimens must also achieve certain additional minimum performance levels for auxiliary (durability) and material tests specific to the product operator type. Generally, improved water penetration resistance and air leakage requirements have been specified for AW products compared to those specified for CW products. Operable AW products are also required to pass the life cycle testing per AAMA 910, which includes 4000 cycles of all operable components, six thermal cycles from 0ºF to 180ºF degrees and repeating air infiltration and water resistance after these tests.

Below is an example of how minimum or gateway requirements for air and water testing change by Performance Class for awning, hopper and projected window products.

*R-PG15 products are tested at 2.92 psf, which is higher than the 15 percent of design pressure, as required for other higher ratings within the R class.

Below is an example of how minimum or gateway requirements change for defection and life cycle testing by Performance Class for awning, hopper and projected window products.

The following is an example of summary data on the first page of the test report for an AW product.

Note: Optional Performance results are listed on page 6 of the report.

Test Completion Date: March 10, 2010