How to Stop Condensation on Windows

Condensation on windows is a common issue in homes, particularly during colder months. It occurs when warm, moist air comes into contact with a cold surface, leading to water droplets forming on windows. While occasional condensation is not unusual, persistent moisture can lead to mould growth, damp problems, and damage to window frames. Preventing condensation is crucial for maintaining a healthy indoor environment and prolonging the lifespan of your windows.

What Causes Condensation on Windows?

Condensation is primarily caused by excess moisture in the air, which settles on cooler surfaces such as windows. Several factors contribute to this issue:

• Warm Air Meeting a Cold Surface – When warm indoor air comes into contact with a cold windowpane, moisture condenses into water droplets.

• High Indoor Humidity Levels – Everyday activities such as cooking, showering, and drying clothes indoors increase humidity.

• Poor Ventilation – Inadequate airflow prevents moisture from escaping, causing a build-up of condensation.

• Single vs. Double Glazing – Older, single-glazed windows tend to be colder, making them more prone to condensation compared to modern double glazing.

Types of Window Condensation and What They Mean

Understanding the different types of condensation can help determine the best solution:

• Internal Condensation (Inside the Glass) – This occurs when warm indoor air meets a cold window surface. It’s a sign of excess humidity and poor ventilation.

• External Condensation (Outside the Glass) – Typically seen on modern, energy-efficient windows. It happens when the outer surface is colder than the surrounding air but is generally not a problem.

• Condensation Between Double Glazing Panes – This indicates that the window seal has failed, allowing moisture to enter. The only solution is to replace the affected glazing unit.

Effective Ways to Prevent Condensation on Windows

Improve Ventilation in Your Home

• Open windows regularly to allow fresh air to circulate.

• Use trickle vents in modern windows to maintain a steady airflow.

• Install extractor fans in kitchens and bathrooms to remove excess moisture.

Reduce Indoor Humidity

• Use a dehumidifier to control moisture levels in high-humidity areas.

• Keep lids on pans while cooking to minimise steam production.

• Dry clothes outside whenever possible or use a vented tumble dryer.

• Keep furniture slightly away from walls to improve air circulation and prevent damp.

Upgrade to Energy-Efficient Windows

• Double glazing with Low-E (low emissivity) coatings helps reduce condensation by maintaining a warmer internal glass temperature.

• Windows filled with argon or krypton gas provide better insulation, reducing temperature differences.

• Investing in A++ rated double glazing minimises the likelihood of condensation forming.

Maintain a Consistent Room Temperature

• Avoid extreme fluctuations in indoor temperatures, which can cause condensation.

• Use central heating efficiently to keep windows at a stable temperature.

• Install thermostatic radiator valves to regulate heat levels in different rooms.

Use Anti-Condensation Treatments

• Window films can help reduce heat loss and prevent condensation.

• Anti-condensation sprays form a protective layer on windows to minimise moisture build-up.

Long-Term Solutions for Homes with Persistent Condensation Issues

For homes with ongoing condensation problems, consider the following long-term solutions:

• Upgrading insulation – Improved loft and cavity wall insulation helps regulate indoor temperatures.

• Installing mechanical ventilation systems – MVHR (Mechanical Ventilation with Heat Recovery) systems extract moisture while retaining heat.

• Checking and improving home drainage – Ensure gutters, downpipes, and damp-proofing measures are functioning correctly.

Common Myths About Window Condensation

• “Condensation only happens in winter” – While more common in colder months, it can occur year-round in humid environments.

• “New double glazing causes condensation” – Well-sealed modern windows can initially show more condensation, as they reduce air leakage, trapping existing moisture inside.

• “Wiping windows every day is a solution” – This only removes condensation temporarily; addressing the root cause is necessary to prevent recurrence.

Preventing condensation on windows requires a combination of good ventilation, humidity control, and efficient glazing. By improving airflow, maintaining a steady temperature, and investing in energy-efficient windows, homeowners can significantly reduce condensation problems, protecting both their property and their health.