Droplets on the room-facing side of a window usually indicate moist indoor air meeting cold glass. Condensation trapped between panes points to a different problem: failure of the sealed glazing unit. The position, timing and recurrence of the moisture are the first clues to the correct repair.
First identify exactly where the water sits
Run a clean dry cloth over the inside of the window. If the moisture disappears, it is on the room side. If it cannot be wiped away from either side of the glazing and looks misty within the unit, the insulating glass seal may have failed. Water on the outer face of double glazing can occur on clear, cool mornings and does not automatically indicate a defect.
Do not assume that every wet window requires new glazing. Replacing a sound window without addressing moisture production or ventilation may leave the same condensation problem in place.
Why condensation is often worse in autumn and winter
Cooking, washing, showering, indoor laundry and breathing all add moisture to household air. Cold window surfaces allow some of that moisture to condense. Bedroom windows may become wet overnight even when they looked clear before bedtime. The UK government’s guidance on existing-home ventilation explains the importance of exchanging moist stale air with fresh air and keeping intended ventilation systems working.
A quick comparison of common symptoms
| Symptom | Likely direction to investigate | First action |
|---|---|---|
| Morning water on inner glass | Indoor humidity and cold surface | Check ventilation and moisture sources |
| Fog permanently between two panes | Failed insulating-glass seal | Ask a glazing specialist to assess the unit |
| Water enters during wind-driven rain | Frame, drainage or external seal | Investigate weatherproofing |
| Black mould around reveals | Persistent moisture, cold bridge or water ingress | Investigate cause rather than repaint |
Check the ventilation before sealing more gaps
Make sure bathroom and kitchen extraction runs and actually moves air, that duct outlets are unobstructed, and that window trickle vents or designed air inlets are not taped shut. A handyman may clean accessible grilles, replace a defective cover or investigate draught seals, but an electrical fault or new fixed wiring calls for an appropriate electrician. Ventilation must be considered as a system; blocking fresh-air paths to stop a draught can worsen moisture.
What a handyman can reasonably check
Useful non-specialist work can include examining damaged perimeter seals, checking whether casements close evenly, looking for obvious blocked frame drainage slots and making minor adjustments within the window manufacturer’s instructions. A technician can also inspect loose internal trim or damaged sealant, provided the cause is understood. Drilling holes into a sealed double-glazed unit is not a normal way to restore its original thermal performance.
Where the water collects tells another part of the story
A little moisture at the bottom of glass differs from water running down walls or soaking a timber sill. Repeated wetting can damage paint, timber and plaster. If condensation is accompanied by persistent mould, staining elsewhere, a strong musty smell or unexplained damp, investigate the wider building. UK damp and mould guidance emphasises identifying and resolving the underlying cause, not treating appearance alone.
Reducing condensation without unrealistic routines
- Use effective extraction during cooking and bathing, and continue it as recommended after use.
- Keep intended ventilation openings functional.
- Dry clothes outdoors or use a suitable ventilated arrangement when practical.
- Maintain sensible, reasonably consistent indoor heating rather than letting rooms become persistently cold.
- Wipe substantial moisture from windows and sills while the underlying issue is investigated.
A portable dehumidifier can help in some situations, but it is not a substitute for repairing leaks, maintaining ventilation or improving a defective installation.
When to use a glazing specialist or surveyor
Persistent mist between panes generally requires evaluation of the glazing unit. Water ingress during rain may require frame or building-envelope diagnosis. A surveyor can be appropriate where damp follows a pattern inconsistent with simple condensation. For rented accommodation, report persistent mould or water ingress to the landlord or managing agent and retain dated photos.
Frequently asked questions
Should I leave a window open all winter?
Not necessarily. Follow the design of your home’s ventilation and use suitable extraction; constant wide opening is not the only strategy.
Will new silicone stop misting between panes?
No. Surface sealant cannot normally restore a failed hermetic seal inside an insulating-glass unit.
Can a handyman repair the cause?
Sometimes—for example, a loose sash or blocked accessible drain. Glazing replacement, complex ventilation alterations and structural damp problems need the appropriate specialist.