Defining and Understanding Window Opening Control Devices

A critical life safety feature in buildings and residences, window opening control devices (WOCDs) are designed for emergency egress through operable windows for occupants and emergency personnel. To simultaneously provide fall protection, these systems must meet strict performance standards. 

To clarify the definition of WOCDs, understand relevant code requirements and gain a better understanding of how these devices work, the Fenestration & Glazing Industry Alliance and the Window & Door Manufacturers Association have released a technical bulletin, AAMA/WDMA TB-24-01. 

These important window fall prevention devices were originally introduced with the 2008 edition of ASTM F2090, Standard Specification for Window Fall Prevention Devices with Emergency Escape (Egress) Release Mechanisms, delineating how to properly test, operate, specify and install WOCDs. 

WOCDs release a window sash to fully open by either two independent single-action devices or one dual-action device. The device then automatically resets when the sash is closed, reverting to its original opening of no more than four inches. 

The release mechanism is designed to prevent accidental activation while still enabling the window to open in an emergency situation without the need for special keys, tools or knowledge. 

Drilling down 

Fall prevention provisions in the building code are triggered when the lowest portion of an operable window opening is more than 72 inches above the finished grade or other surface below on the exterior of a building, and the dimension from the finished floor to the lowest portion of the window opening is less than 24 inches or 36 inches, depending on the building occupancy type and/or state or local code requirements. 

When fall prevention requirements are applicable, the code requires use of a device that is compliant with ASTM F2090 – either a WOCD, a window fall prevention guard or a specialized window screen. If the window opening is not required for emergency escape and rescue, the code allows simply limiting the opening dimension of an operable window such that it would prevent the passage of a four-inch diameter sphere or a non-operable window can be installed. 

For those openings greater than 75 feet above grade, devices must comply with ASTM F2006, Standard Safety Specification for Window Fall Prevention Devices for Non-Emergency Escape (Egress) and Rescue (Ingress) Windows. However, such devices should not be installed on openings required for emergency escape and rescue because they are not designed to be released, but rather act more as barriers that are more permanent in nature. 

WOCD operation 

To better understand single- and dual-action mechanisms, an example of the former is a lever that can be flipped on, with two such devices installed on the same window. A dual-action device requires two separate, distinct and consecutive actions to release the WOCD; for instance, pushing in one button and, while holding that button in, sliding over a lever. 

For single- or double-hung windows, the standard requires either two independent single-action devices or one dual-action device per window, located above the top of the bottom sash. For a sliding or gliding window, the mechanism is located at the sill. In both cases, the egress release mechanisms must be readily visible when the sash is in the fully closed position, or when the window sash has reached the controlled open position, or both. The WOCD must then automatically reset. 

With a casement, awning or hopper window, the sash is attached to the frame by the metal arm. By pushing a button inward toward the window jamb, and sliding upward vertically, the arm is released to fully open the window. When the window is closed, the WOCD automatically resets. 

While currently referenced in U.S. building codes, some provinces in Canada are also considering including ASTM F2090 in their local codes. 

As a member of the Window Safety Task Force, FGIA offers additional window safety resources for more information on preventing window falls. 

The full AAMA/WDMA TB-24-01 technical bulletin is available as a free download at the FGIA Online Store.