Most modern windows are equipped with double or triple glazing in the form of insulated glazing units (IGUs). These IGUs have an airtight seal at the perimeter that traps some type of gas between the window panes—usually argon, but sometimes krypton or ordinary air.
Ideally, the IGU perimeter seal is permanent. If the IGUs are filled with argon or krypton—gases that improve the IGU’s energy performance—you don’t want any of the precious gas to leak out. Moreover, you never want any humid air to enter into the space between the glass panes, since the entry of humid air can lead to condensation between the panes (sometimes called fogging).
IGUs perform well when they are installed at an altitude close to that of the factory where the IGUs were assembled. However, if IGUs from a sea-level factory are transported to a job site at a high elevation—usually defined as a location above 5,000 or 6,000 feet—then all kinds of bad things can happen:
Window experts have been aware of the problems associated with high-altitude installations of IGUs for decades, and many technical articles address the problems. Back in 2000, for example, BuildingGreen published an article on the topic called “High Elevation Problems Jeopardize Gas-Fill Windows.”
The article referred to a class action lawsuit against Hurd Windows, in which the plaintiffs alleged that certain Hurd Windows may not have had the U-factor promised by the manufacturer, since argon may have leaked out of so-called “breather tubes” installed to address issues related to high-altitude installations. In response to the suit, Hurd Windows eventually agreed to a $5.3 million settlement.
The large settlement shook up the window industry. After the Hurd settlement, almost all window manufacturers understood the need to carefully examine available options to address these high-altitude installations.