Double Glazed Window Repairs Double glazing can cause problems over time, including fogs between the glass or frames that are rotting. These are easy to fix and repair may be cheaper than you think. Make sure to contact the company from whom you purchased the item to determine if there is a warranty. It's worthwhile to try fixing any issues on your own first. Sealing upvc window repair seals (also known as upvc window repair seals) play an important part in the insulation of double-glazed windows. Seals that are not properly installed can cause condensation, drafts and other problems. Fortunately damaged seals can be repaired or replaced to restore the efficiency of your double glazing. The most obvious sign that double-glazed windows require sealing is water leakage between the glass panes.