Understanding Double-Paned Window Cracking During Storms: An Inside and Outside Explanation

During a storm, a double-paned window might crack on the inside or outside, a phenomenon that often baffles homeowners. While it's a common misconception that the gas layer inside the window cannot crack, various factors can contribute to such events. This article delves into these factors to provide a clearer understanding of window cracking during storms.

The Anatomy of a Double-Paned Window

Double-paned windows, also known as insulating glass (IG) units, consist of two panes of glass separated by a space filled with a special gas, usually argon or krypton. This helps to improve energy efficiency by reducing heat loss. Each pane has specific surfaces: surface 1 and 2 are on the outside pane, and surface 3 and 4 are on the inside pane. These designations are important for handling, installation, and maintenance, as surfaces can have different coatings such as UV film, shading film, or impact film.

Why Does a Double-Paned Window Crack?

Glass cracks due to two main reasons: impact or stress. Most often, the glass cracks due to stress generated within the window frame. This stress can be caused by various factors, including violent winds during a storm.

How Storms Affect Double-Paned Windows

During a storm, the pressure inside and outside the window equalizes, typically through tiny gaps or inconsistencies in the building's seal. This pressure drop can cause the gas layer between the panes to push outward, leading to slight bowing of the glass. If there is a flaw or crack, the pressure may cause the glass to break.

Cracking can occur either on the inside or outside of the window. If a crack starts on the inside, it might be due to:

Pressure differences caused by the storm Existing flaws or defects in the manufacturing process Small, invisible flaws that became significant over time Indirect forces from activities inside the house, such as opening or closing windows

If a crack starts on the outside, it could be due to:

Direct impact from flying debris High wind pressure Improper installation or positioning of the window

Getting a New Window

If your windows are under warranty (typically from 5 to 15 years), you can usually request a replacement. This warranty covers manufacturing defects, which may be the cause of the cracking. It's important to have the window evaluated by a professional to determine the exact cause and whether a replacement is necessary.

Conclusion

While it's common to assume that only the outside of a double-paned window can crack, both inside and outside cracking can occur during storms. These cracks are usually due to stress and pressure differences, and they can be covered under warranty. Understanding these factors helps homeowners make informed decisions about their windows and how to maintain their energy efficiency and safety.