Failed seals, what can be replaced without changing the frame, and how to avoid a repeat.
Misting between the panes is not condensation you can wipe off — it means the sealed unit has failed and moisture is inside the cavity. Once that happens, the insulating performance of that unit is gone.
The good news is that this is usually a glass problem, not a window problem.
The perimeter seal is exposed to constant thermal movement. Over years it can break down, especially where drainage is poor and water sits against the bottom edge of the unit. Once the desiccant in the spacer bar is saturated, misting appears.
If the frame is sound and the hardware works, the sealed unit alone can normally be replaced. It is far cheaper than a new window and it is an opportunity to upgrade the glass specification at the same time.
If the frame is distorted, the hinges are failing, drainage is blocked by design or several units have failed across the same window, replacing the window is usually the better long-term decision.
Send a photo of the affected windows and we'll advise whether it's a glass job or a window job.
Drilling and drying treatments do not restore the seal or the insulating gas fill. Replacing the unit is the reliable fix.
Sealed units usually carry their own guarantee period. It's worth checking the original paperwork before paying for replacements.
Most common obscure patterns are still available, and we'll confirm the match before ordering.