How To Stop Condensation On Your Windows

Condensation on windows is an inconvenience in colder months, but if left untreated, it can lead to serious problems and shouldn’t be ignored.

Condensation can damage windows and furniture, cause mould and be detrimental to health.

Getting to the real cause of the problem is the only way to stop condensation from forming on windows and on walls inside your home. The first step is figuring out what is causing the excessive moisture in your home, and the solutions include improving ventilation and keeping a stable temperature.

There are three types of condensation that can happen on your windows and we cover all of them below.

We will also answer a few common questions at the end.

What Is Condensation?

Condensation is created by excess moisture in the air that forms on cold surfaces. Usually, on windows, when it’s colder outside than inside.

The air around us contains lots of microscopic droplets of water that we can’t see. When it’s more humid, the water content becomes more concentrated and more likely to ‘condense’ on surfaces.

Imagine a glass of iced water on a hot day that looks like it’s sweating. This is a result of the moisture in warm air colliding with the cold surface of the glass.

In warm air, the molecules are spaced far apart and this ‘holds’ the moisture, but in cool air, the molecules come together. When the molecules become close enough together, they merge into visible liquid. This is known as the 'dew point'.

At the dew point, we can see the drops of water form on a surface. Think of:

• Condensation on a mirror after a shower
• Kitchen window steamed up when cooking
• Moisture on windows when drying clothes indoors

Condensation doesn’t just form on windows, it can form on any cold surface. Especially in areas where moisture can become trapped:

• Windows that have blinds or curtains
• Behind large furniture against a cold wall
• Inside a fitted wardrobe on an external wall

Why Does Condensation Happen?

Condensation happens because rooms get too cold, they fluctuate between cold and hot, and there is excessive moisture from cooking, washing and expiration.

The biggest causes are showering, drying clothes on radiators and boiling pans. Underlying issues of damp can also be a persistent problem. But the main causes are usually day-to-day living habits.

Not turning on heating to save on bills is also a major contributing factor as moisture forms on cold surfaces.

Condensation will always form on the coldest surfaces in a room and that is usually noticed on window panes. Although walls can also have condensation, but it can be less noticeable than glass.

Types Of Window Condensation

Condensation is always most noticeable on your windows and your windows are a great barometer for how efficient your ventilation and condensation control is.

You might just think condensation is condensation, but there are three types that can happen on your windows and all happen for a different reason and have different solutions:

1. Internal pane condensation

This is the most common type of condensation and appears on the internal surface of your windows inside your home. 

You’ll typically notice it first thing in the morning, especially in bedrooms, bathrooms and kitchens where humidity naturally increases through daily activities like sleeping, cooking or showering. 

Homes that are well-insulated and airtight are also more prone to internal condensation because moisture has fewer escape routes.

Internal condensation is generally a ventilation issue, not a window fault. Improving airflow is key, whether that’s through trickle vents, extractor fans, opening windows regularly, or reducing moisture at its source. In some cases, upgrading to higher-performing glazing can help by keeping the internal glass surface warmer, reducing the temperature difference that triggers condensation.

2. External pane condensation

Condensation on the external face of your windows outside can confuse homeowners, but it is usually a sign that your windows are performing extremely well.

This type of condensation forms when the outer pane becomes colder than the surrounding air, typically overnight when temperatures drop and humidity is high.

With efficient double and triple glazing, little warmth reaches the external pane of glass so the surface stays cool enough to allow moisture in the early morning air to settle on it. This is completely natural and usually clears quickly once the sun rises or the air warms up.

External condensation is not a fault and doesn’t mean there’s a problem with your windows. In fact, it indicates that the glazing is insulating effectively. 

3. Between panes condensation

Misting between the panes of double or triple glazing is the one type of condensation you should never ignore. 

If moisture appears inside the cavity, the sealed space between the panes, it means the seal around the glass unit has failed. Once this seal is compromised, the insulating gas escapes and moisture-laden air enters, leading to misting, fogging or water droplets within the unit.

Unlike internal surface condensation, this cannot be wiped away, and unlike external condensation, it does not clear on its own. Over time, the insulating performance of the window decreases, making your home less energy-efficient and potentially increasing heating bills.

The only effective solution is to replace the failed sealed unit. In many cases, the frame can stay in place and only the glass unit needs replacing, but if the window is older or has multiple failures, replacing your windows is the only solution. If your windows are still under warranty, sealed-unit failure is typically covered, so it’s worth checking before arranging repairs.

How can condensation damage windows?

Simple Steps To Stop Condensation On Your Windows

The way to reduce condensation is through a multi-layered approach where all three of these factors are critical:

• Ventilation
• Reducing internal moisture 
• Maintaining stable indoor temperature 

In addition to this, for persistent and excessive condensation, you might need to consider insulation of the fabric of the building, such as the windows, floor, roof and doors, to help keep a stable temperature.

How To Improve Ventilation To Reduce Condensation

There are a few options to improve ventilation in your home:

Airflow/MEV system

Many new apartments are built with internal airflow systems to combat the problem. These systems use a network of ducts in the ceiling to extract and exchange air from the outside to inside. 

This maintains air circulation and a humidity balance within a property that is well-sealed.

Retrofitting a ventilation system in a house is invasive and expensive and not always possible in older houses.

PIV Unit

For an easier-to-install solution, Positive Input Ventilation (PIV) units can be fitted in areas that produce excessive moisture. Such as kitchens and damp basements.

The unit extracts the humid air from inside the house and draws in ‘dry’ air from the outside. This exchange of air helps to maintain the humidity balance.

Extractor fan

Having sufficient extraction in a bathroom is essential to reduce the excessive humidity produced by showers. Some fans have humidity control and will allow the fan to operate automatically if the humidity level increases above a set level.

Kitchens also need good extraction systems for cooking to remove smoke, smells and moisture.

Air vents/bricks

Air bricks often get blocked to stop draughts, but they do work to keep an area ventilated. A simple vent will ensure the humidity is managed in a room, but this does have the result of energy efficiency being reduced. For this reason, air bricks are not as popular as they used to be.

Air vents in windows do work to help with ventilation and stop condensation on the window. They can be installed on most windows.

Opening windows

Traditional windows were used to provide effective ventilation, which was essential when most homes were heated by fossil fuels.

• Sash windows were designed to allow for the bottom and top to be opened, that would draw air in and out, providing effective ventilation.
• Bay windows were designed to have two casement windows on either side to allow superior draw and ventilation.
• Transom windows above a door were designed to increase airflow around a property to move heat around internally and to ventilate.

Modern windows all have multi-point lock settings to allow them to be left open securely for ventilation. This is one of the simplest and easiest ways to keep your home ventilated and avoid condensation. However, if it is raining or excessively damp in the air, keep windows closed to stop the humidity from coming inside.

Reducing Moisture To Reduce Condensation

In combination with ventilation, reducing moisture is essential to stop condensation. The average household produces a considerable amount of water vapour each day just from normal living activities.

Something you might overlook, expiration from houseplants and pets also contributes to water moisture in the air and condensation. Although some houseplants can actually help to reduce condensation.

The biggest causes of excess moisture that cause condensation

All of these areas should be addressed to try and minimise the impact they have on contributing to humidity in the house:

• Cooking, boiling pans and kettles
• Showers and hot taps
• Washing machines and tumble dryers
• Drying clothing on radiators or indoor airers
• Large houseplants
• Wet logs stored for wood burners
• Unfound water leaks in cavities or under floors
• Rising damp in basements and ground-level buildings

Maintaining Stable Indoor Temperature And Heating Patterns

The air will always retain some levels of moisture, so the other critical factor to address is to ensure surfaces are not cold.

Condensation happens when moisture hits cold surfaces and what you don’t want is an internal fluctuation of temperature. The ideal scenario is for temperature internally to be a stable median consistent all the time.

Setting your central heating at a low temperature all the time is far better than letting a room go very cold and then blasting it with high-temperature heating. For example, when you go out to work and then return home. 

This is where energy efficiency at home is critical to ensure you can achieve and retain a consistent temperature at all times.

Having insulated doors and quality double or triple glazed windows can help to maintain temperature without an excessive energy bill.

How To Stop Condensation In Your Bedroom

Bedrooms are one of the most common places to find condensation because of natural expiration while we sleep. Every person breathes out warm, humid air throughout the night, and in a well-insulated room with the door closed, that moisture has nowhere to escape, leading to droplets on windows and damp patches around frames by morning.

To reduce bedroom condensation, the key is to improve ventilation and manage humidity overnight:

1. Increase airflow during the night

If safe to do so, keep trickle vents open or leave the window slightly open to let air circulate. Even a small amount of continuous ventilation can make a big difference to morning condensation levels.

2. Keep internal doors slightly open

A closed bedroom stops the air from circulating, so leaving the door ajar allows moisture to disperse into the rest of the home, where it can dissipate.

3. Maintain a consistent temperature

Cold rooms encourage condensation, as warm air from your breath hits cold surfaces and cools rapidly. Keeping the bedroom at a gently heated, stable temperature overnight helps prevent these temperature swings.

4. Avoid drying clothes in the bedroom

Drying laundry in a bedroom releases litres of moisture into the air, dramatically increasing condensation. Move drying racks to well-ventilated rooms instead.

5. Position furniture away from external walls

Large wardrobes or beds pushed against cold walls can trap moisture and create cold spots where mould can grow. Leaving a small gap behind furniture helps air circulate.

By combining good ventilation with stable heating and a few simple lifestyle changes, you can significantly reduce bedroom condensation and create a healthier, more comfortable sleeping environment.

Can Double Glazing Stop Condensation On Windows?

The reason we see so much condensation on single glazed glass is that the glass is susceptible to cold and stimulates the dew point from the water vapour in the air.

Double glazing helps to reduce condensation because the glass is not as cold as single glazed. The air gap inside the double glazing sandwich helps to keep the internal pane of glass closer to room temperature. This difference in temperature is enough to stop the water vapour from reaching the dew point and forming condensation on the glass.

Double glazing can’t eliminate condensation entirely, so following a combined approach of windows, ventilation and reduced moisture is the only way to completely get rid of condensation.