Three Classic Examples
By Charles C. Roberts, Jr., Ph.D., P.E.
Window sash damage is a common building problem addressed by claims personnel. In- surance 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
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 conden-sation. 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.