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Window Classification by Performance Standards


Performance-based standards for windows and doors rate completely fabricated products according to how they perform under actual job site conditions. They compare key performance attributes of different manufacturers’ windows of the same type and grade for a given application.

These essential performance characteristics are structural performance under wind loading and the level of resistance to air leakage, water penetration and forced entry. Other performance requirements for specific window types (casement, horizontal sliding, etc.), as well as for optional energy efficiency attributes (thermal performance and condensation resistance), can be referenced to meet specific markets or job criteria.

The specifier or product designer determines the level of performance desired under defined conditions. Then, factoring the characteristics of the material and components into the equation, the manufacturer builds a window that meets the specified performance level. In general, the required performance drives the product’s design.

The industry recognizes five Performance Classes, each of which addresses the needs of a particular market segment by requiring increasingly stringent basic performance requirements:

Each of these performance classes are commonly used as follows:

  • Residential (R): used in one- and two-family dwellings.

  • Light Commercial (LC): used for low- and mid-rise multifamily dwellings and other buildings where larger sizes and higher loading requirements are expected.

  • Commercial Window (CW): used in low- and mid-rise buildings where larger sizes, higher loading requirements, limits on deflection and heavier use are expected.

  • Architectural Window (AW): 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.

The table below compares the basic parameters for Performance Classes as related to the Performance Grade (Design Pressure), Structural Pressure and Water Resistance: