Post fabrication valving

In this approach, a secondary fabrication process is needed at, or near, the installed location. It typically involves using a one-way valve installed into either the IGU spacer or one of the glass panes before gas filling occurs. Such valves are specified and designed to be mechanically depressed under a specific differential pressure load to adjust the pressure in the cavity relative to the atmospheric pressure at the manufacturing site. After venting, the valve returns to a closed position, usually under a spring load. This method requires the valve to remain uncovered during transport for pressure adjustment after installation of the IGU.

When the IGU is glazed, the valve can be actuated to allow proper pressure equalization venting. Placement of setting blocks and glazing sealant should be evaluated when locating the valve to avoid restricting airflow of the valve outlet. Additionally, mechanical loading of the valve by framing material could cause stress in the sealing and mounting of the valve should be verified to prevent moisture or gas leakage.

The IGU must be specified and designed to have sufficient strength to perform under cyclical thermal loads, seasonal temperature changes, and at the venting pressure of the valve. Calculations will ensure the proper valve is used so the IGU’s final internal pressure at the time of installation will be within the design limits of the edge seal.

Conclusion

Each of these pressure equalization methods and their associated application guidelines is covered in thorough detail in IGMA TM-3200-21. For each approach, this manual addresses advantages and disadvantages, and provides factory-to-field recommendations for manufacturing and quality, storage and shipping/handling, installation (glazing), and considerations for dealing with environmental conditions to which the IGU will be exposed at all stages. Commercially available software programs which can address the germane variables and predict the glass deflection also are listed in the manual.

Author

Amy Roberts is Fenestration and Glazing Industry Alliance’s (FGIA’s) director of Canadian and technical glass operations. She oversees FGIA’s Canadian standards and regulatory building and energy codes, as well as the Insulating Glass Manufacturers Association of Canada (IGMAC) certification program for insulating glass units (IGUs). Roberts has more than 20 years of industry experience in glass and insulating glass (IG) manufacturing, and in both residential and commercial window manufacturing.