Window sash damage is a common building problem addressed by claims personnel. Insurance coverage of window related losses is often dependent on the nature of the damage and whether it occurred as a result of one incident or over time. Pane breakage, rotted frames, foggy double panes, and jammed frames are among the many problems that perpetuate insurance related claims. The following are three classic examples of window sash losses that serve to illustrate the issues faced by the claims analyst.

1) Interior Moisture Damage
Moisture damage to windows can occur from the inside, primarily from condensation on window components during the winter. High humidity levels mean moisture laden air condenses on cold surfaces such as single pane glass and window sash without thermal breaks. Without proper maintenance the sash deteriorates as exemplified in the window shown in Figure 1 to the right.

Humidity levels in the home are often a result of personal lifestyle choices and significantly affect the deterioration of window sash. Some insured's prefer unusually high humidity in the home, which can accelerate window sash deterioration if appropriate maintenance is not performed.

Defective humidification units in a home may lead to higher humidity levels, exacerbating deterioration of window sash. For the past 30 years, window frames have been constructed with thermal breaks that tend to reduce cold areas that encourage condensation. Some thermal breaks have been improperly designed, allowing significant cold transfer and increased condensation. These problems occur over time.

2) Sash Deterioration Defect
Older sash was constructed of hard woods with closed cell structures, which minimized the damage from water as compared to modern sash, which utilizes soft woods with an outer, water-resistant cladding. Figure 2 to the right shows an example of a modern casement window 10 years after installation, well within the warranty period.

Rain water has penetrated the outer aluminum protective cover and has rotted the bottom of the sash. This area is typically unseen by the home owner and becomes noticeable when there is difficulty opening or closing a window. The rotted bottom of the sash near the sill does not retain a square shape, causing jamming of the window while opening.

Figure 3 to the right is a close-up of the deteriorated wood where water became trapped after penetrating the outer cladding.

The windows were properly installed and maintained. A design defect exists in that water could easily bypass the seal and accumulate in an area that did not drain or dry out readily.

Researching recalls by the window manufacturer may reveal a recall as was the situation in this case where the manufacturer acknowledged the defect and gave a prorated credit to the homeowner for the failure during the warranty period.

Of course, water can enter a properly designed window system as a result of improper installation, handling damage (shipping) or other external damage (rocks from lawn mowers) suggesting that an inspection of the window system may be necessary.

3) Building Structural Movement
Structural movement of a building can cause problems with window systems. Deflection of the building structure can occur from settling, nearby construction, excessive loading, defective construction, deterioration of the structure, foundation movement and wind. Building deflection in the form of racking causes the window frame to distort, resulting in sash failure, window cracking and jamming when the window sash is raised or swung outward (Refer to Figure 4 to the left).

The damage can occur suddenly as a result of high wind pressure or excavation close to the building. The damage can also occur gradually as exemplified by settling or structural deterioration. The window in Figure 5 to the left suffered from cracking and deformation of the sill.

As evident in Figure 6 below, a rotted support beam (arrow) under the sill that is deflecting downward. Brickwork also attests to the downward deflection of the support beam, a long term deterioration related problem.

As in most losses, it is prudent to inspect the window system and obtain information from the insured as to the particulars of the problem with the window system. This may include:

The age of the window.
When the damage was first noticed.
Or any coincident circumstance, etc.

Photographs from the underwriters or an aerial (satellite photo) view of the home may show evidence of a preexisting condition.

Special Reports /

Technical Notebook: Window Sash Damage: Causes and Coverage

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