Why Is My Window Foggy?

Foggy windows can affect visibility, comfort, and energy efficiency in a home. While this may seem like a minor inconvenience, persistent fogging—especially between glass panes—often points to a deeper issue requiring attention. Allied Glass & Aluminum Products Ltd has long served the Victoria area with expertise in residential and commercial glass solutions, in this blog we will discuss the causes of fog on windows and what can be done to fix the issue.

What Causes Window Fogging?

Window fogging typically results from the interaction between temperature differences and moisture. There are three main types of condensation:

• Interior condensation: Appears on the inside surface of windows when warm, moist indoor air contacts the cold window glass. This usually happens in winter and is often linked to high indoor humidity.

• Exterior condensation: Forms on the outside surface, typically in the early morning or during humid conditions. It’s a natural result of outdoor humidity and temperature shifts and generally does not require repair.

• Between-pane condensation: This is the most concerning type, occurring when the seal on a double- or triple-pane window fails. Once this seal is compromised, moisture enters the air gap, creating fog or cloudiness between the panes.

Causes of Seal Failure

The most common reason for fog inside a window unit is a seal failure in insulated glass units (IGUs). These are double- or triple-pane windows with a sealed air space between the layers. Seal failure can occur due to:

• Age: Older windows are more likely to experience seal degradation over time.

• UV exposure: Continuous sunlight weakens the seals, especially in south- or west-facing windows.

• Poor installation: Improperly installed glass windows may place pressure on the seals, leading to premature failure.

• Moisture intrusion: Leaks in the window frame or surrounding structure can also compromise the seal.

When a seal fails, the insulating gas inside the panes escapes, and moisture takes its place, resulting in foggy or streaked windows. This often indicates the need for glass repairs to restore the window's performance.

When to Consider Repair

Persistent fog between window panes is not just a cosmetic issue. It may reduce energy efficiency and, over time, lead to damage to surrounding materials due to excess moisture. Homeowners should consider window glass repairs when:

• Fog obstructs visibility and natural light.

• Energy bills increase due to reduced insulation.

• Mould or rot appears near the window frames.

• The condition of the glass continues to worsen.

A professional assessment may be required to determine whether repairs can address the issue or whether glass replacement is more appropriate.

Supporting Window Clarity and Performance

Maintaining clear and functional windows plays an important role in indoor comfort, energy efficiency, and home aesthetics. Fogging can signal deeper problems, especially when it occurs between panes of glass. Understanding the root causes and addressing them with the right repair solution helps protect the long-term condition of your glass windows.

Allied Glass & Aluminum Products Ltd, in Victoria, has extensive experience with residential and commercial glass concerns. Contact our professional team to discuss your window glass repair requirements and request a quote today.