Haven’t the Foggiest? What You Need to Know About Fogging Windows in Claims

Double-paned windows are the most popular types of residential windows in the United States. They’re particularly susceptible to fogging, which compromises the functionality and aesthetics of the affected windows. Fogging is typically caused by age-related deterioration of the glass seals, resulting in condensation between the panes. Adjusters should verify the cause of loss before making claims decisions, ensuring they have the most complete information available.

Which Windows Are Susceptible to Fogging?

Window fogging occurs in double-paned or triple-paned windows. Double-paned windows are standard in new home construction and as replacement windows, making them the most common type of residential window. They have a higher R-value than single-paned windows, resulting in greater energy efficiency. Triple-paned windows have an even higher R-value, but they are rare in residential construction or as replacements; they are more commonly used in commercial settings.

A double-paned window consists of two panes of glass separated by a spacer within the frame, which keeps the two panes in place. The spacer contains a desiccant that absorbs moisture to prevent condensation. The space between the panes can be filled with air or a dry, inert gas, forming an insulating gap. A flexible sealant prevents air movement and keeps out moisture. However, if the sealant fails, moist air may become trapped in the air gap, leading to fogging.

The two glass panels, air gap, desiccant, and sealant make double-paned windows more energy efficient, but if a seal is compromised, humid air may be trapped between the panes, leading to window fogging.

What Causes Window Fogging?

Window fogging is the result of humid air entering the gap between the two panes. This is typically caused by age-related deterioration of the window’s sealant, which is the most common point of window failure. As the sealant deteriorates, the seal is broken, and moisture in the air is introduced to the gap. As the trapped air heats up from sunlight, it expands and forces air out of the broken seal. Then as the window cools, the panes contract, causing the window to suck humid air in between the panes. Condensation forms between the panes, obscuring the glass. Moist air may also introduce minerals into the gap, which may build up into mineral deposits over time.

This window has sustained sealant failure caused by age-related deterioration, which has led to fogging and discoloration due to mineral deposits.

Many factors may cause stress to the windowpanes, frames, and seals, leading to sealant failure. These factors include:

• Repeated opening and closing of the window
• Repeating opening and closing of nearby doors
• Repeated exposure to water
• Expansion and contraction caused by temperature fluctuations
• Changes in atmospheric pressure
• Daily changes in wind direction
• Environmental pollutants
• Exposure to radiation from the sun

The sealant in south- and west-facing windows will typically deteriorate faster than those in the structure’s other windows because of the greater sun exposure. It’s also possible that birds, rain, hail, or other objects can contribute to the deterioration of the sealant, but such impacts will rarely break the seal of an otherwise functional window.

How Do We Investigate Window Failures, Like Fogging?

Donan’s licensed forensic engineers follow the same process when evaluating a window failure, whether or not fogging is the reported cause of loss. They consider:

• The date of any recent weather events
• The age of windows/replacement windows
• The type and source of the windows
• Previous structural damages and repairs
• Any other problems, such as binding, water intrusion, etc.

We consider the age of the windows because it’s possible for double-paned windows to sustain sealant deterioration after as few as 10 years, leading to condensation between the panes. We also consider other sources of failure, such as damaging winds, which are likely to leave other collateral indicators, including downed tree limbs, damaged roof coverings, or dented gutters or downspouts.

When evaluating a window claim, Donan Engineering provides a comprehensive report to answer questions about the failure.

Adjusters can avoid settling for unnecessary window replacements by working with Donan Engineering. Our nationwide network of window experts can verify the cause of loss and scope of damage.

Submit an assignment to receive actionable intelligence you can use to make informed decisions about your next windows claim.