Condensation on Windows: Causes and What to Do

Water droplets on your windows can be frustrating, especially when they return every morning or leave the sill wet.

Condensation forms when water vapour in the air meets a surface cold enough for it to turn into liquid. On windows, the first useful question is where the moisture is: on the inside surface, outside, or between the glass panes.

Those are different situations. Knowing which one you can see helps you describe the problem without having to diagnose it yourself.

Condensation on your windows: what to check first

Location: can you wipe it from the room-facing surface, or does it appear outside or trapped between panes?
Timing: does it appear overnight, after cooking or showering, or throughout the day?
Pattern: is one window affected, one room, or most of the home?
Effect: does it clear, pool on the sill, or appear alongside mould or damaged finishes?
Changes: did it start after new windows, ventilation work or another repair?

Check only what you can safely reach. You do not need to climb outside or dismantle anything.

If you rent, report persistent moisture, mould, damage or suspected window faults through your landlord’s usual repair channel.

Why is there condensation on the inside of my windows?

Moisture enters indoor air through ordinary activities such as cooking, showering, drying laundry and breathing. If the window surface becomes sufficiently cold, some of that moisture can condense on the glass.

The amount you see depends on the moisture in the air, surface temperature and how effectively moisture leaves the home.

It does not automatically mean the window is faulty. Equally, recurring condensation should not simply be dismissed as something the resident has caused.

Heating, insulation and ventilation can all be relevant to understanding persistent moisture problems. Our guide to how ventilation works in your home explains trickle vents, extractor fans and other systems.

Why does condensation appear every morning?

Windows can become colder overnight, allowing moisture to collect on the glass. You may first notice it when you open the curtains.

Instead of treating every wet window as the same problem, note what happens next. Does the moisture clear during the morning? Does it remain all day? Is there water collecting on the sill?

For example, “the bedroom window is wet most mornings and the sill remains damp at lunchtime” gives more useful context than “the windows are bad”.

A morning pattern alone does not establish the cause or show whether the ventilation system is adequate.

What does condensation on the outside mean?

External condensation can occur on modern, well-insulated glazing because the outer glass stays cold while less heat escapes from indoors.

It may clear as the sun warms the glass or the weather changes. Outside condensation by itself does not automatically indicate a window defect.

You might see it on some panes but not others because their position and surroundings differ. Pilkington’s window guidance explains this distinction.

If you are unsure where the moisture sits, describe that uncertainty when asking for advice.

What if the moisture is between double-glazing panes?

Misting trapped between the panes of a sealed double- or triple-glazed unit is different from droplets on the room-facing surface.

It can indicate failure of the sealed glazing unit and needs assessment by an appropriate professional. Ventilating the room or wiping the accessible glass will not repair a failed unit.

If you rent, report the affected window to your landlord. Record whether the misting stays in the same area and whether it changes over time. Do not attempt to dismantle or reseal the glazing yourself.

This explanation concerns sealed glazing units; separate secondary glazing has a different arrangement.

What can you safely do about indoor condensation?

Practical steps can help manage moisture while you report any persistent problem:

Wipe accessible water droplets and dry the sill.
Use kitchen and bathroom extraction as intended.
Keep trickle vents open and unblocked.
Use pan lids when cooking.
Where possible, dry laundry outdoors; if that is not possible, explain your circumstances when seeking advice.
Open windows when appropriate and safe, taking account of security and your household’s needs.

Follow instructions for any mechanical ventilation system. Report fans that stop working or vents that are damaged.

The government’s existing-home ventilation guide explains why moisture removal and background ventilation matter.

These steps are not a guarantee that condensation will stop, and they do not replace investigation of a possible property problem.

When should you report it to your landlord?

Report persistent indoor condensation, repeated pooling water, damage, broken ventilation or misting between sealed panes.

If damp or mould appears, report it promptly rather than waiting to collect a complete set of photographs. Explain any health concerns or effects on your household.

Government guidance says landlords should investigate underlying causes of damp and mould. Resident advice should not substitute for addressing those causes.

Our damp-and-mould guide explains what to do, while how to report a repair to your landlord helps you make a clear report.

If the affected room also feels unusually cold, our cold-room guide suggests observations worth sharing.

What should you record?

Keep the record simple:

The room and specific window.
Dates, times and photographs.
Where the moisture appears.
Whether it clears or returns.
Any pooling water, mould or damage.
Previous reports, inspections and work.
Changes after a repair or window replacement.

For example: “Since the bedroom window was replaced, moisture has collected on the inside most mornings. Photos show the window and sill on three separate dates.”

Describe what you observed without assuming the replacement caused it. Clear observations can help landlords and contractors compare current conditions with previous work and decide what needs investigating.

Keep the window problem connected to your home’s history

Use your House Krowd account to keep photographs, observations and repair updates together. Continue reporting concerns through your landlord’s usual channel too.

After an inspection or repair, note what was done and whether the moisture returns. Our guide to what to record after a completed repair explains how to keep that follow-up connected to the original issue.

Knowing your home means noticing useful patterns, not having to become a building expert.

Sources and further reading

This guide provides general information, not a diagnosis of your home. The government rented-housing guidance linked above applies to England.

Why Does Condensation Keep Forming on My Windows?