Introduction to Condensation in Double Glazing

Condensation in double glazing got you down? Discover comprehensive solutions for tackling this pesky issue and preserving the efficiency of your windows.

condensation in double glazing

For many homeowners, double glazing is synonymous with energy efficiency, improved security, and noise reduction. It’s a modern-day essential, giving homes the kind of insulation that not only enhances comfort but also contributes to a greener, more sustainable lifestyle. However, a common and often perplexing issue that many individuals encounter is condensation in their double-glazed windows.

If you’ve ever woken up on a chilly morning to find your double-glazed windows fogged up with water droplets, you’ve experienced the frustrating phenomenon of condensation. This can be confusing and frustrating because double glazing is supposed to offer superior thermal performance. The occurrence of condensation raises several questions. Is it indicative of a fault in the window? Is it compromising the energy efficiency of your home? What can you do to prevent it?

This article is a comprehensive guide aimed at demystifying the issue of condensation in double glazing. Whether you’re a new homeowner grappling with this for the first time or you’ve been dealing with it for a while, this guide will provide valuable insights into why condensation occurs, how to prevent it, and when to seek professional help. We will explore the science behind double glazing and condensation, the various types of condensation you may encounter, and delve into both preventative and curative measures.

So, if you’re plagued by condensation and are looking for answers, you’ve come to the right place. Let’s dive in and unpack everything you need to know about this prevalent issue in the world of double glazing.

What is Double Glazing?

Double glazing, a term that you might have heard often but perhaps never fully understood, is a type of glazing for windows and doors that uses two panes of glass rather than just one. These two panes are separated by a gap that can be filled with air or special gases like argon or krypton. This might sound simple, but this design is ingeniously effective at providing superior thermal insulation compared to a single pane of glass.

The Anatomy of a Double-Glazed Unit

In a typical double-glazed unit, the two glass panes are secured within a frame, which can be made of various materials like uPVC, aluminum, or wood. The gap between these panes can range between 12-20 mm, depending on the design and purpose. Some double-glazed units also feature advanced coatings on the glass that further enhance their thermal or acoustic properties.

Why Double Glazing?

The primary reason for the popularity of double glazing is its excellent thermal performance. The gap between the glass panes acts as an insulating barrier that hampers the transfer of heat, thereby helping to keep your home warm during winters and cool during summers. This insulating effect significantly reduces your need for artificial heating or cooling, leading to reduced energy bills.

But the benefits don’t stop at thermal performance. Double glazing is also effective at:

  1. Noise Reduction: The additional pane and insulating gap act as a barrier to noise, making double glazing ideal for homes near busy roads or airports.
  2. Enhanced Security: Double glazing is tougher to break than single glazing, making it a deterrent for burglars.
  3. Reduced Condensation: Although not completely foolproof, double glazing can mitigate the issues of condensation to some extent, when properly installed and maintained.

Common Materials Used in Double Glazing

Different frame materials offer different benefits and drawbacks:

  • uPVC: Durable and low-maintenance but less effective as an insulator compared to wood.
  • Aluminum: Strong and sleek but can be less insulating than other materials unless it comes with a thermal break.
  • Wood: Excellent insulator but requires more maintenance and can be more expensive.

Understanding the different elements that constitute a double-glazed unit can help you make an informed choice when you decide to install or replace double-glazed windows in your home. Given the complexity and variety of options available, it’s crucial to assess your specific needs and consult professionals for tailored advice.

What is Condensation in Double Glazing?

At its most basic, condensation might seem like a simple and harmless occurrence: water droplets forming on a surface. However, when it comes to windows, particularly double-glazed ones, the issue can become much more complex and concerning. Condensation occurs when water vapor in the air converts into liquid form upon coming into contact with a surface that has a lower temperature.

The Science Behind Condensation

To fully understand condensation, it’s important to dig into the science behind it. Air contains water vapor, and the warmer the air, the more water vapor it can hold. When warm air comes into contact with a cold surface, it cools down and can no longer hold the same amount of water vapor. As a result, the excess moisture is released, forming water droplets on the cold surface—this is condensation.

Why Does It Happen on Windows?

Windows are typically the coolest surfaces in a room, particularly in winter. Since they are in direct contact with the external environment, they can get much colder compared to the indoor walls. This makes them a prime location for condensation to occur, especially if the indoor air is humid.

Types of Condensation on Windows

When it comes to condensation on windows, not all condensation is created equal. The location and manner in which condensation forms can tell you a lot about the condition of your windows and even your home’s overall health. Let’s explore the various types of condensation you might encounter on your windows.

Surface Condensation

Definition and Causes

Surface condensation is perhaps the most visible and common type of window condensation, occurring either on the interior or exterior surfaces of the glass. Interior surface condensation is typically caused by high levels of indoor humidity coming into contact with a cold window surface. Exterior surface condensation occurs when humid outside air meets the colder surface of the window from the inside of the home.

Implications and Prevention

While generally harmless, surface condensation can be annoying and may obstruct your view. Over time, it can also cause paint to peel or discolor. Effective ventilation, moisture control, and even the use of dehumidifiers can help manage surface condensation.

Hidden Condensation

Definition and Causes

Also known as concealed condensation, this type occurs within wall cavities, attic spaces, or even inside the window assembly itself. It’s often a result of poor insulation and inadequate ventilation. Because it’s hidden from view, homeowners usually discover this type of condensation too late, making it particularly concerning.

Implications and Prevention

Hidden condensation can cause significant structural damage over time, including wood rot and mold growth, which can be health hazards. This type of condensation often requires professional evaluation and solutions, which may include improving insulation or installing proper ventilation systems.

Between the Glass Condensation

Definition and Causes

This occurs when moisture appears between the panes of your double-glazed windows. It’s a strong indicator that the sealant holding the glass panes together has failed, allowing moisture to infiltrate the space that should be airtight.

Implications and Prevention

When you see condensation between the glass, it means that your double-glazed window is not functioning as it should. Your windows will lose their insulating properties, and in the worst cases, you may need to replace the glass unit entirely. It’s crucial to address this issue promptly to restore the efficiency of your double-glazing.

By understanding these types of condensation and their implications, you’ll be better equipped to identify and address the problems you’re facing. It will also guide you on whether you can handle the issue yourself or if you need professional intervention.

Why Should You Be Concerned?

While a little bit of condensation now and then is generally not a problem, consistent or heavy condensation can have several detrimental effects:

  1. Structural Damage: Prolonged exposure to moisture can damage window frames, particularly wooden ones.
  2. Mold Growth: Moist conditions are ideal for mold, which can have health implications.
  3. Reduced Visibility: Heavy condensation can impair visibility through the window, which can be particularly problematic for drivers or in emergency situations.

By understanding what condensation is and why it happens, you’ll be better equipped to tackle the problem head-on and find effective solutions, which we’ll discuss later in this guide.

How to Prevent Condensation in Double Glazing

If you’re grappling with condensation on your double-glazed windows, you’ll be pleased to know that there are several effective preventative measures you can take. Let’s delve into some of these solutions:

Proper Ventilation


Proper ventilation is crucial for ensuring good air circulation within your home, which in turn helps to eliminate moisture and reduce condensation.


  • Open windows periodically, especially during and after activities that produce a lot of moisture, such as cooking or showering.
  • Consider installing exhaust fans in high-humidity areas like bathrooms and kitchens.

Use of Dehumidifiers


Dehumidifiers can play a significant role in reducing indoor humidity levels, which is one of the leading causes of window condensation.


  • Place a dehumidifier in rooms where condensation is most problematic.
  • Ensure the dehumidifier is appropriate for the size of the room for maximum effectiveness.

Temperature Control


Maintaining a consistent temperature can mitigate the extremes that often cause condensation to form on windows.


  • Use thermal curtains to keep cold air out and warm air in.
  • Maintain a consistent thermostat setting to avoid rapid temperature fluctuations.

How to Treat Condensation in Double Glazing

If preventative measures fail or you’re already facing a condensation issue, don’t despair. Here are some ways to treat the problem:

DIY Methods

Interior Condensation

  • Using a Squeegee: For surface condensation, a simple squeegee can help remove water droplets effectively. It’s a quick and cost-effective method.
  • Absorbent Cloth: Microfiber cloths can also be useful in absorbing moisture and can be easily washed for reuse.

Exterior Condensation

  • Application of Anti-Fog Solutions: There are commercial solutions available that can be applied to the exterior glass to reduce condensation.

Professional Help

Between-the-Glass Condensation

  • Window Replacement: In extreme cases where condensation occurs between the glass panes, the seal has likely failed, and you may need to replace the entire window unit.
  • Resealing: Some professionals can remove the pane, clean the inside, and reseal it, although this is usually a temporary solution.

By understanding both preventative and treatment options, you can take a comprehensive approach to dealing with condensation in your double-glazed windows.

FAQ Section

  1. Why is there condensation on the inside of my double glazing?
    • This is often due to high humidity levels.
  2. How do I get rid of it?
    • Consider using a dehumidifier or improving ventilation.
  3. Is it a sign of a problem?
    • Not necessarily, but consistent condensation should be checked.


Understanding the causes and treatments for condensation in double glazing can save you both time and money. It’s important to assess the situation carefully and take appropriate measures to ensure your home remains comfortable and efficient.

Additional resources

Energy Saving Trust’s advice on windows

Window Condensation: Top 10 Fixes

How Double Glazing Works