You open the curtains in the morning and the window is wet again. Wiping it dry helps. Until tomorrow.
Condensation on the inside of your windows usually means there is a lot of moisture in the air and that this moisture is settling on the colder glass. It can be caused by showering, cooking, sleeping or drying laundry indoors, but also by insufficient ventilation.
Where the condensation appears already tells you quite a lot. On the outside, it is usually nothing to worry about. On the inside, ventilation is often the first thing to check. Is the moisture between two panes of glass? Then the insulating glass is probably no longer properly sealed.
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Condensation on the inside, outside or between the glass?
Before you start cleaning ventilation grilles or booking a professional, first check exactly where the moisture is. It makes quite a difference.
Condensation on the inside of the window
This is the type you usually need to do something about. Warm, humid air hits the colder glass and turns into small water droplets.
A little condensation after showering or cooking is not immediately a problem. But if your windows are soaking wet every morning, water runs down the glass or black marks appear around the frame, too much moisture is probably staying inside your home.
Things to check: ventilation grilles, mechanical ventilation, airflow and how much moisture is being produced in the room.
Condensation on the outside of the window
Do you wake up to condensation on the outside of the glass? In most cases, you do not need to repair anything.
With well-insulated glazing, the outer pane can become quite cold during the night. Moisture from the outside air can then condense on it. Once the temperature rises, it usually disappears by itself.
In that case, your window is essentially doing its job.
Condensation between double glazing
Can you not wipe the moisture away from either the inside or the outside? Then the condensation may be between the panes.
This usually means that the sealed cavity between the panes is leaking. The insulating glass has lost its proper seal.
Cleaning will not solve that problem. The glass needs to be assessed and usually replaced.
Condensation between the panes? Have a glazier inspect the window →
What causes condensation on the inside of windows?
Condensation itself is fairly simple. There is moisture in the air and it comes into contact with a cold surface. The more useful question is why enough moisture stays inside your home to make the windows wet every day.
1. A lot of moisture is produced indoors
Showering, cooking, breathing, mopping and drying laundry indoors all add moisture to the air.
That does not have to be a problem as long as the moisture can also escape. If you produce a lot of moisture and ventilate too little, cold glass is often the first place where you notice it.
2. Not enough fresh air enters the room
Opening a window for five minutes is not the same as continuous ventilation.
If you have ventilation grilles, they need to be open and clean. If you close them because it is cold outside, you are not only keeping the cold out. You are keeping the moisture in as well.
No ventilation grille in a room that is repeatedly damp? Installing one can provide a more permanent solution.
View ventilation grille installation →
3. The mechanical ventilation is not working properly
Many homes use mechanical ventilation to remove humid air from the bathroom, toilet and kitchen.
If you notice hardly any extraction, the bathroom stays humid for a long time or the ventilation unit is unusually quiet, check whether the system is still working properly.
A ventilation system that is there but does very little is mainly a fairly large box attached to the ceiling.
4. The glass or frame becomes very cold
The colder the glass, the faster moisture condenses on it. That is why condensation is more common in winter and more common on older windows or particularly cold parts of a property.
But even modern glazing can develop condensation on the inside if the humidity level indoors is high enough.
5. Your home has been insulated, but the ventilation has not kept up
Sealed gaps, new frames, better glazing. Good for reducing heat loss.
But air that previously moved in and out naturally through small gaps no longer does so. Proper ventilation therefore becomes even more important as a home becomes more airtight.
How can you find the cause yourself?
You do not immediately need to replace anything. A few simple checks can often tell you a lot.
1. Check where the condensation is
Inside, outside or between the panes? This is the first and most important distinction.
2. Check when it happens
Mainly in the bedroom in the morning? Moisture from breathing combined with limited ventilation is probably playing a role.
Mainly during and after showering? Check the bathroom ventilation.
After cooking? Check how humid cooking air is being extracted.
3. Check your ventilation grilles
Are they open? Are they free from dust? Is there a curtain, cupboard or another object blocking the airflow?
Ventilation grilles are fairly simple pieces of equipment. They just work considerably less well when they are permanently closed.
4. Check the mechanical extraction
Hold a thin sheet of paper against an extraction vent, for example in the bathroom. If it is clearly pulled towards the vent, there is at least some airflow.
If you notice hardly any difference between the different settings or there is no extraction at all, it may be worth having the ventilation system checked.
5. Check whether it affects one window or the whole property
Is only one window constantly wet? Then the position or the glazing itself may be part of the problem.
Are several windows, the bathroom and perhaps even cold walls damp? That points more towards a broader ventilation or moisture issue.
Do you also see damp patches on the walls? Read more about how to distinguish leaks, rising damp, penetrating damp and condensation.
What can you do right now about condensation?
Is the window wet this morning? You do not need to spend three weeks investigating before doing anything.
Dry the glass and frame.
Keep ventilation grilles open and clean dirty grilles.
Increase mechanical ventilation during and after showering and cooking.
Use extraction while cooking and avoid producing unnecessary moisture.
Avoid letting the home become very cold for long periods.
Make sure air can move between rooms.
A moisture absorber can reduce a small, temporary moisture problem. But if you need to dry the window every morning, that is mainly a sign that you need to deal with the cause.
Can you solve condensation yourself or do you need a professional?
Things you can do yourself
Always start with the simple things:
open and clean ventilation grilles;
ventilate properly while sleeping, cooking and showering;
use extraction systems;
dry wet bathroom surfaces after use;
check whether air can move freely through the property.
Does the condensation clearly reduce afterwards? Then you also have a good indication of where the problem was coming from.
When is a more permanent solution sensible?
If your windows remain wet every day despite proper ventilation, there is little point in experimenting forever.
There may not be enough fresh-air supply. The mechanical ventilation may not be working properly. Or the problem may be in the glazing itself.
At that point, investigating the cause makes more sense than buying another moisture absorber.
Which professional do you need for condensation on windows?
Not enough fresh-air supply
If there is no ventilation grille or the existing grille needs replacing, a glazier can install a suitable ventilation grille in or around the window.
Have a ventilation grille installed →
Mechanical ventilation is not working properly
If humid air is no longer being removed properly and the ventilation unit turns out to be old or defective, have the system checked. If replacement is necessary, a heating or ventilation professional can carry out the work.
Replace mechanical ventilation →
Condensation between double glazing
In that case, additional ventilation will not solve the problem inside the window itself. Have the glazing inspected by a glazier.
When should you take condensation seriously?
A little moisture on the window from time to time is usually not an urgent problem.
Do not leave it too long if:
the windows are completely wet almost every morning;
water runs down the window or over the frame;
black mould appears around the window or on walls;
paint, sealant or wallpaper starts to come loose;
wooden frames remain damp for long periods;
the property continues to smell musty;
the mechanical ventilation no longer works;
you cannot work out where the moisture is coming from.
At that point, condensation is no longer just a window you need to wipe occasionally. It becomes a moisture problem that can cause damage.
How does a professional solve the problem?
That depends on the cause. A good solution therefore does not automatically start with replacing something.
Identify the cause. Where is the moisture being produced and how is the room ventilated?
Check air supply and extraction. Are grilles, vents and ventilation systems present and working?
Determine the appropriate solution. For example, installing a ventilation grille, repairing or replacing mechanical ventilation, or dealing with defective glazing.
Carry out the work and check the result. After the job, the system or installation is checked to make sure it works properly.
What happens if you do nothing about recurring condensation?
A misted window seems fairly harmless. And that is usually how it starts.
If the moisture returns every day, window frames and surrounding finishes can remain damp for long periods. Paint can peel, timber can be affected and mould can develop on cold, damp surfaces.
The pattern is usually:
too much moisture → condensation → persistently damp surfaces → mould or damage.
That is why drying the window is not the real solution. You want to prevent so much moisture from being left behind in the first place.
How can you prevent condensation from returning?
The most important step is making sure humid air can continuously leave the property and fresh air can enter.
Keep ventilation grilles open as much as possible.
Clean grilles and extraction vents regularly.
Keep mechanical ventilation running and temporarily increase the setting when showering or cooking.
Regularly check whether the extraction system is still working.
Avoid allowing humid air to remain trapped in one room for long periods.
If there is no option for continuous fresh-air supply, read more about the cost of installing a ventilation grille in a window.
How much does it cost to solve condensation on windows?
That mainly depends on the cause.
Cleaning an existing ventilation grille costs virtually nothing. Installing a new ventilation grille is a relatively small job. Replacing a ventilation unit or insulating glass is obviously more extensive.
So do not jump straight from the symptom to an expensive solution. First establish why the window is getting wet. Then you know what you are actually paying to fix.
For ventilation grilles, you can view the current ventilation grille price guide.
What do customers say about ventilation jobs through Zoofy?
When dealing with condensation, the goal is not to get even more information about humidity. You want the cause dealt with and the job completed properly.
A customer who had a ventilation grille installed through Zoofy wrote:
“The job went well. Good communication and everything was left neat and tidy.”
A customer who booked work on mechanical ventilation described the experience as:
“Job completed properly. Good communication, skilled work and friendly service.”
These experiences come from customers who had these specific jobs carried out through Zoofy.
Frequently asked questions about condensation on windows
Is condensation on the inside of windows normal?
A small amount of condensation can occur, for example after sleeping, showering or cooking. If the windows remain wet for long periods almost every day, it is worth checking ventilation and moisture production.
Why do I mainly get condensation on bedroom windows?
While you sleep, breathing adds moisture to the air. Bedrooms are also often relatively cool. With limited ventilation, condensation can therefore form easily on the window.
Why do I mainly get condensation in winter?
Windows and other surfaces are colder in winter. Warm, humid indoor air therefore condenses more quickly when it reaches those cold surfaces.
Does opening a window help with condensation?
Airing the room can quickly remove a lot of moisture. For a structural solution, continuous ventilation is more important, for example through ventilation grilles or a properly functioning ventilation system.
Does a moisture absorber help against condensation?
A moisture absorber may temporarily remove some moisture, but it does not solve insufficient ventilation or another structural moisture problem.
What does condensation between double glazing mean?
Condensation between the panes usually points to a failure in the seal of the insulating glass. You cannot wipe this moisture away yourself. A glazier can assess whether the glass needs replacing.
Do your windows keep getting wet? Deal with the cause
You can, of course, wipe the window dry again tomorrow morning.
And the morning after that.
That works perfectly well for the water that is already there. Slightly less well for the reason it keeps coming back.
Not enough fresh-air supply? Have a ventilation grille installed.
Is your mechanical ventilation no longer working properly? View mechanical ventilation replacement.
Is the condensation between the panes of double glazing? Have a glazier assess the glass.
Then you will not have to start with that cloth again tomorrow.
My name is Wilm, a construction and home improvement expert at Zoofy, with many years of experience in the construction and renovation sector. Over the years, I have supervised countless projects, ranging from small maintenance jobs to full-scale renovations. This hands-on experience has taught me how essential transparency in pricing and quality is for every project.
At Zoofy, I share my knowledge about construction costs, pricing, and smartly comparing jobs. Whether it’s the cost of a painter, a plumber’s hourly rate, or the price of a complete bathroom renovation, I help you understand what a fair price is and what to look out for.
My goal is to make home improvement projects more transparent, so everyone knows where their money goes. By combining up-to-date pricing information with real-world experience, I make it easier to find the right professional—without any surprises afterward.