Where the condensation appears matters
- On the room side: the air inside is too humid or the glass is cold. Ventilation and lower humidity solve it.
- On the outside: it appears on cool mornings on glass that insulates well. This is normal and clears on its own.
- Between the panes: the insulated glass unit is no longer sealed. This is the only case where the glass must be replaced.
Why condensation forms between the panes
An insulated glass unit has two or three panes, separated by a spacer and sealed around the edges. The spacer contains a material that absorbs any moisture left inside.
Over time, the edge seal can fail because of age, large temperature swings, poor installation or an impact. Humid air gets between the panes, the absorbent material becomes saturated and condensation appears.
What happens if you do not replace it
The glass does not become dangerous, but it insulates less well, and the condensation leaves deposits between the panes that cannot be cleaned. Over time, the problem shows up more often.
Replace the glass or the whole window?
If the frame and sash are in good condition, only the glass unit is replaced. It is quicker and cheaper than a new window.
If the profiles are warped, the hardware no longer closes properly or the frame seals are destroyed, replacing the window is also worth discussing.
How the glass is replaced
- The glass is measured on site: dimensions, thickness and type of glass.
- A new unit is ordered with the same thickness, so it fits the existing profile.
- The glazing beads holding the glass are removed and the old unit is taken out.
- The new unit is fitted on the correct setting blocks, so the window does not sag and closes properly.
- The beads are refitted and the closing is checked.
How to reduce condensation on the room side
- air the room briefly and often, especially after showering and cooking;
- use the cooker hood and the bathroom extractor fan;
- do not cover the radiator under the window with heavy curtains;
- do not dry laundry in unventilated rooms.
Frequently asked questions
Can the glass be repaired without replacing it?
There are methods for drying the space between the panes, but the seal is not restored to factory standard and the problem can return. The reliable solution is to replace the glass unit.
Can the glass be replaced in timber or aluminium frames?
Yes. The glass unit can be replaced in timber, PVC or aluminium frames, as long as the profiles are in good condition.
Does the whole window need replacing if only one pane has condensation?
No. Only the affected glass unit is replaced.
