Condensation on the inside of double glazed windows: causes and solutions
Not sure whether your misty window needs new glass? First, check where the moisture is. Condensation on the room-facing surface is different from mist trapped between the panes. JJ’s Glass & Glazing helps homeowners in Leicester and the surrounding area assess their glazing and replace failed double glazed units where needed.
Where is the condensation?
- On the inside surface: if it wipes off from inside the room, indoor moisture is condensing on cold glass. This alone does not mean the sealed unit has failed.
- Between the panes: mist you cannot wipe away from either accessible surface can indicate a failed sealed unit.
- On the outside: external condensation can occur on energy-efficient glazing and does not, by itself, mean the window is faulty.
Why does condensation form inside?
Moist air releases water onto glass when the surface is cold enough. Cooking, showers, drying clothes indoors and normal everyday living all add moisture. Limited ventilation lets that moisture build up. Double glazing helps keep the inner pane warmer, but it cannot remove moisture from the room.
How to reduce surface condensation
- Use kitchen and bathroom extractor fans during moisture-producing activities.
- Keep existing ventilation openings clear and use trickle vents as intended.
- Ventilate rooms regularly when safe and practical.
- Reduce indoor clothes drying where possible, or ventilate the drying space.
- Wipe away standing water and check whether it returns.
If persistent damp affects walls or several rooms, investigate the wider moisture and ventilation problem. Replacing glass alone may not solve it.
When should the glass unit be replaced?
If moisture is trapped inside the sealed cavity, ask for a glazing assessment. Where the frame is suitable and in good condition, replacing the double glazed unit may be possible without replacing the whole window. Opening windows or wiping the glass cannot remove moisture trapped within a failed sealed unit.
Double glazed unit replacement in Leicester
JJ’s Glass & Glazing replaces misted and broken down double glazed units, as well as individual glass panes. We cover Leicester and surrounding areas within approximately 40 miles. Send a photo of the affected window, your location and an indication of how many panes need attention. We can discuss the next steps and arrange accurate measurements where needed.
Unsure what you need? Use our Request a Quote page and explain whether the moisture wipes off or appears trapped inside the glass.
Common questions
Does internal condensation always mean failed double glazing?
No. Moisture on the room-facing surface often relates to humidity and cold surfaces. Moisture between the panes needs a different assessment.
Will replacement glass stop all condensation?
No guarantee can be made. The cause matters: indoor humidity and ventilation still need attention.
Do I need new frames?
Not necessarily. We assess whether your existing frame can accept a replacement sealed unit.
Further guidance: Glass and Glazing Federation consumer guides and Energy Saving Trust window advice.