PERFORMANCE: Codes & Standards

North American Fenestration Standard

The North American Fenestration Standard/Specification for windows, doors and skylights (AAMA/WDMA/ CSA 101/I.S.2/A440) provides a method for rating the structural performance, water resistance and air leakage of fenestration products. Ratings determined in accordance with this standard can be used to show compliance with the air leakage requirements of building energy codes and with ASCE 7, the calculation method for wind loads in the International Building Code.

Under the 2008 version of this standard, windows can achieve one among four performance classes depending on the stringency of test conditions and the achieved ratings:

R Class: Commonly used in one and two family dwellings.

LC Class: Commonly used in low- and mid-rise multifamily and other buildings where larger sizes and higher wind loading requirements are expected.

CW Class: Commonly used in low- and mid-rise buildings where larger sizes, higher wind loading requirements, limits on deflection, and heavy use are expected.

AW Class: Commonly used in mid- and high-rise buildings to meet increased loading requirements and limits on deflection, and in buildings where frequent and extreme use of the fenestration products are expected.

Depending on the performance class, qualifying products must meet minimum requirements for sample size and structural and water resistance test pressure, as well as additional test requirements. To qualify for any of the performance classes, most windows must have a tested air infiltration rate no higher than 0.3 CFM/ft2. AW class windows are tested at a higher pressure than R, LC and CW class windows.

The following organizations can provide more information on the North American Fenestration Standard:


Facade Design Tool



Window Technologies

Case Studies

Tools & Resources