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How to stop condensation on windows

Aug 15, 2023Aug 15, 2023

If left untreated, condensation on windows can obscure your view and lead to mould growth, peeling paint and even structural damage.

While a level of condensation is inevitable, especially during damper, more humid weather, it’s always worth checking that your windows aren’t constantly wet and streaming.

In many cases, you can reduce condensation through a combination of ventilation and dehumidification.

Read on to discover what’s causing the condensation on your windows and learn effective ways to stop it.

At its core, condensation forms when warm, moist air interacts with a colder surface, causing the moisture in the air to convert into water droplets. This is a natural phenomenon; when air is saturated with moisture and can no longer hold any more water vapour, the excess moisture has to go somewhere.

If the air meets a cold surface, such as a windowpane, it cools down quickly and loses its capacity to hold moisture, causing the excess to condense into liquid form.

Steeper gradients in temperature (the difference between the temperature inside and outside) lead to more condensation.

Condensation varies from a light covering of steam to large, streaming water droplets that soak window sills.

A plethora of day-to-day activities inadvertently contribute to heightened levels of indoor moisture.

This, in turn, increases the likelihood of condensation forming on various surfaces within your home.

A hot shower is a prime culprit for elevating humidity levels in a bathroom. When you indulge in a steamy shower, hot water evaporates into the air, substantially boosting its moisture content.

This humid atmosphere becomes conducive to condensation, especially when it encounters cooler surfaces, including bathroom mirrors or windows.

To mitigate this effect, you might install an extractor fan or ventilate the room during and after the shower.

While taking one or two showers daily is unlikely to cause significant issues, if the shower is used multiple times per day, surfaces can become especially moist without adequate ventilation.

Cooking activities, particularly those involving boiling water or frying food, release a substantial amount of steam into the air. This moisture-rich air accumulates quickly, particularly if the area is poorly ventilated.

The coolest surfaces in the room, such as your kitchen windows, often attract that condensed moisture.

To alleviate this issue, use extractor fans or open a kitchen window to improve ventilation.

Drying clothes indoors can significantly elevate the moisture levels in your living space. As your clothes dry over time, the water they contain evaporates into the air.

In an under-ventilated room, this moisture has nowhere to go and will likely cause condensation inside windows.

If you have no choice but to dry clothes inside, use a dehumidifier to reduce air moisture levels, and make sure to open windows.

Condensation can be caused by a number of day-to-day activities, but simple steps can help to prevent build-up and potential damage. (Adobe)

Houseplants – particularly broad-leaved plants, such as the Monstera variety – are often overlooked sources of indoor moisture.

Plants release moisture into the air through a process called transpiration. While this is generally good for air quality, an abundance of houseplants in a confined space can increase humidity, causing condensation on walls and windows.

This may become an issue in conservatories during damp and humid weather.

Human activities, such as breathing and perspiring, also release moisture into the air, especially in damp and cool environments.

Moisture is more likely to build up when there are several people in a house or room.

Some areas in your home are more prone to developing condensation, potentially leading to mould and other serious issues.

In these “trouble spots”, air tends to stagnate, increasing the likelihood of moisture settling on cold surfaces. And since many of these spots are somewhat hidden from view, you may not realise they’re harbouring a damp problem.

Here are some key areas to keep an eye on:

Blinds and curtains can trap air between the fabric and the windowpane. This trapped air cools down more quickly than the air in the rest of the room, leading to condensation.

If these coverings are made of materials that absorb moisture, such as thick fabrics, the problem can become worse. Further, curtains and other fabrics can quickly attract mould and mildew if they remain damp for too long.

Placing large pieces of furniture, such as wardrobes and sofas, against an exterior wall can reduce air circulation.

The wall itself will likely be colder than the room’s average temperature, especially in winter.

This setup creates a pocket of cooler, stagnant air behind the furniture, where moisture can easily condense.

Fitted wardrobes, especially those situated against an external wall, are prime spots for condensation.

The wardrobe’s interior can become much cooler than the room itself, particularly if it’s made from materials that don’t insulate well.

Add to this the poor air circulation within wardrobes and you have an environment where condensation can quickly form on the back panel or even on your clothes.

You might not check the back of the wardrobe often, so any minor mould problems could quickly spread if you don’t stop them early.

Many people are concerned about excess condensation on windows, as this may indicate a damp home that harbours mould and mildew.

It’s important to note that some condensation on the inside of windows is perfectly normal. This indicates that the windows are providing an effective barrier between the inside and outside of your home. Issues arise when condensation doesn’t clear promptly or when it’s so excessive that it begins to stream down windows and penetrate other surfaces.

Condensation on the inside of windows can lead to aesthetic and structural damage, as well as black mould growth. (Adobe)

Condensation forming on the exterior surface of windows is most commonly seen during the warmer months.

This phenomenon indicates that your windows are doing an excellent job of keeping the interior of your home insulated.

Essentially, the warmer, moist air from outside hits the cool surface of the window and condenses. While it can be somewhat annoying, particularly if it obstructs your view, it’s usually not a cause for concern.

This type of condensation is a natural occurrence and doesn’t tend to lead to moisture-related issues, such as mould growth or structural damage.

Condensation on the inside of windows is a more serious issue and generally occurs in cooler temperatures.

When the external temperature drops, the internal surface of the window becomes cooler than the air inside the room.

If there’s a high moisture level in the indoor air, it will condense on the colder surface of the window.

Keep an eye on this form of condensation, as it can quickly lead to mould and mildew problems if left unchecked for extended periods.

It’s not unusual for people to notice condensation after installing new windows.

Initially, this can be concerning, but it’s usually attributed to the enhanced insulation properties of the new windows. The temperature differences between the internal and external surfaces should level out over time, and the overall condensation and moisture levels should decrease.

While new windows should reduce interior moisture problems by lowering air leakage, it’s still paramount to ventilate your home.

The presence of condensation on double– or triple-glazed windows indicates that moisture has found its way between the glass panes. If you notice condensation forming between the layers of glass, this may be a sign that the sealant has failed, which can be a significant issue.

Replacing or repairing the sealant may suffice in some cases, especially if you don’t notice condensation forming there often.

However, if it becomes a chronic issue or the inside of the windows is visibly wet and streaming, consider replacing the window.

Some level of condensation on the inside of windows is inevitable, especially when exterior temperatures cool and we begin to heat our homes.

However, persistent or severe condensation can inflict cosmetic and structural damage to your windows and even pose a risk to your health if it triggers mould growth.

Black mould commonly forms from uncontrolled moisture levels and can cause many health issues, including headaches, irritation and respiratory failure.

If you find a black mould problem, it’s crucial to act swiftly to prevent it from spreading.

The consistent and frequent formation of water droplets on windows can damage their surface coating, such as paint or varnish.

Wooden windows are more vulnerable, as excessive moisture can cause the wood’s paint or varnish to soften, lift and eventually peel away.

Not only does this degrade the appearance of the windows, but it also exposes the underlying wood to moisture, potentially leading to further damage.

Persistent moisture can upset the natural balance of wooden frames and sills, leading to drying and cracking over time.

When the wood eventually dries, it may non-uniformly contract, resulting in cracks that pull the fibres apart.

Cracked wood can provide convenient crevices for mould growth, further exacerbating the problem.

Perhaps the most alarming issue resulting from constant window condensation is the growth of black mould. Black mould, Stachybotrys chartarum, is the most common and notorious type of mould that forms inside homes.

Black mould releases mycotoxins into the air, which can be harmful when inhaled. It can be challenging to eliminate established black mould. Clamping down on internal moisture is a front-line defence against black mould. If you encounter it, aim to remove it as soon as possible.

Black mould is the most common and menacing form of interior mould, but it’s certainly not the only type you may encounter. Virtually all forms of mould and mildew thrive in a damp, humid environment.

It’s unrealistic to completely prevent condensation from forming on your windows, especially in cooler, damper weather.

However, persistent or severe condensation can quickly develop into an issue.

Here are some practical techniques for preventing condensation on windows:

Proper ventilation is crucial for reducing indoor humidity levels.

Simple measures, such as keeping a window open during and after cooking or while using the bathroom, can significantly reduce condensation buildup over time.

Simple steps, such as opening a window in a kitchen or bathroom can help with humidity and condensation, but some homes might require greater effort in the form of a dehumidifier and extractor fans. (Adobe)

Reducing moisture at the source can prevent condensation. For instance, cover pots while cooking to prevent steam from escaping, and dry clothes outside if possible.

Drying clothes is a significant issue, as wet clothes can hold litres of water, which has to go somewhere when you dry them inside. If you need to dry clothes indoors, consider using an electric dryer or try to place them near a window and comprehensively ventilate your home. You can also place a dehumidifier near your clothes to suck up any excess moisture.

Some dehumidifiers have a “laundry mode” that’s explicitly designed for this purpose.

Double- or triple-glazed windows are excellent for reducing condensation, as they offer better insulation, preventing the steep temperature gradient that often leads to excessive condensation in single-glazed windows.

They also provide the added benefit of reducing energy bills due to their superior insulating properties.

Laundry can significantly raise the humidity levels within your home. In addition to taking care with how you dry your clothes, you can also wash your clothes in colder water whenever possible. Colder washes (below 40 degrees) are effective for most types of laundry and consume less energy, making them more sustainable. If you use a dryer, ensure it’s vented to the outside to prevent moist air from accumulating indoors.

Cooking, especially boiling and steaming food, releases considerable moisture into the air.

One simple but effective tactic to contain this moisture is to always use lids on your pots and pans.

Additionally, use extractor fans if you have them, or open windows to allow the steam to escape.

Personal hygiene activities, including showering and bathing, are another major source of indoor humidity – especially for larger families or groups of people.

You can manage this by considering the length of your showers and baths, opting for shorter ones whenever possible.

Extractor fans, if present, should be turned on during the shower and left running for several minutes afterwards to expel moist air.

Beyond these activities, consider investing in moisture-absorbing plants or using moisture-absorbing products, such as silica gel packs, in areas where moisture accumulates.

Regular maintenance checks for leaks in plumbing and seals can also prevent unexpected sources of moisture.

Dehumidifiers and air purifiers with dehumidifying functions can be employed in the bathroom, but care should be taken when using electrical devices in bathrooms.

Limited condensation on inside windows is generally not a cause for concern so long as your home is otherwise damp-free. However, consistent, severe condensation is worth tackling, as this can lead to mould issues.

The first lines of defence against excessive condensation are ventilation and dehumidification.

Always ventilate your home when drying clothes and cooking food or when you have a lot of people in a single room.

In many cases, placing one or more dehumidifiers around your home will effectively reduce humidity to 60 per cent and below, which dramatically reduces the chance of mould formation.

Drying clothes inside without adequate ventilation is one of the prime culprits; always try to dry outside if possible. Otherwise, consider using an electric dryer. Failing that, dry clothes near an open window and suck up excess moisture with a dehumidifier.

Window vacuums can effectively remove some condensation, but they don’t address the root cause of the problem: excessive humidity. They’re more of a quick fix than a permanent solution.

Learning how to get rid of condensation inside windows generally involves a blend of clamping down on humidity and ventilating the home.

A dehumidifier can be effective at reducing indoor humidity levels, thus helping to prevent window condensation.

They come in many sizes to accommodate different spaces and are particularly useful in rooms where moisture accumulates, such as bathrooms and kitchens. If you’re wondering how to stop condensation on windows overnight, ventilating the house or using a dehumidifier is a good option.

Many people notice increased condensation in the morning. This is generally because the temperature drops overnight, and the colder window surfaces can cause moisture to condense more readily.

Constant moisture and condensation can lead to mould growth, which poses health risks, especially for those with allergies or respiratory issues. Learning how to stop window condensation is important for spotting and controlling mould issues.

Sam Jeans

Sam is an experienced writer whose expertise lies in home improvements and renewables, as well as technology, where he is especially interested in the world of machine learning and AI. He has written for Vested, Age Times, and the Royal Mint.

For the Independent Advisor, Sam writes about windows and solar panels.

Condensation on a bathroom mirror or window after a showerSteamed-up kitchen windows during cookingMoisture on windows when drying clothes indoorsCondensation on interior walls due to houseplantsHuman respiration and perspirationWindows with blinds or curtainsSpaces between large furniture and cold wallsInside a fitted wardrobe on an external wallCondensation on outside of windowsCondensation on inside of windowsCondensation on new windowsCondensation between the panes of double- or triple-glazed windowsPeeling of window paint or varnishDrying and cracking of the wood trimBlack mouldImprove ventilationReduce moistureInstall double- or triple-glazed windowsWhen washing your clothesWhile cooking in the homeWhen showering or bathing