How To Prevent & Deal With Condensation In Double Glazing?

It is not a pleasant scene when you see condensation in double-glazed windows and units. Sadly, this is quite a frequent sight if you reside in the United Kingdom. That’s because of the humid climate, especially during wet winters or even autumn, when the mercury starts to dip after summer.

Double-glazed condensation is a common issue with homeowners in the UK that can significantly impact the well-being of residents. Infestation of black mould on the cill and frames of the windows can easily occur. When the mould spores spread, they will likely cause breathing-related problems in humans and pets.

In such a scenario, you definitely want to know the effective solution to prevent condensation in double-glazing windows and units. Read on…

Understanding Condensation 

The process of condensation involves the conversion of vapor or gas into its liquid state, i.e., water. When the temperature of the window pane or glass drops below the dew point* condensation can occur. The dew point largely depends upon the humidity of the air. Condensation can occur when the air temperature is high, and humidity levels are increased. Additionally, it can also happen at lower temperatures (in colder months) with lower humidity levels.

* Dew Point: The dew point is the temperature at which air becomes saturated with moisture, converting water vapor into liquid water, such as dew or fog, when cooled further.

Why Condensation is Problematic?

Condensation in double-glazed windows may be rare as it is most likely to occur in single-glazed windows, where there’s only one pane of glass separating indoor and outdoor temperatures.

  • Condensation is detrimental to both the longevity of your windows and the well-being of property residents.
  • Additionally, it can degrade the window quality faster, especially if sealed units are exposed to moisture for a long time. 
  • From mould infestation to frame damage, your windows tolerate a lot.

However, double-glazed window condensation on the inside or outside should not misconstrued as faulty windows. You must consult with professionals to assess the windows and guide you on the best ways to resolve the issue.

Common Areas of Condensation in Double-Glazed Windows and Solutions

Double-glazed window condensation on the inside


  • Poor Ventilation/excessive Humidity: This occurs mostly due to poor ventilation or excessive humidity indoors. Since the indoor temperature is low, the window surfaces become colder than the outdoor surfaces, promoting condensation of the warm air. 
  • High Moisture levels: Similarly, certain areas in your property like the kitchen or bathroom, where the moisture level is high, condensation is very common on the inner surfaces of cold windows.
  • New construction/renovation: Humidity levels are usually high in newly constructed properties or those that have recently been renovated due to paint, wet plaster, and drying concrete. It’s quite shocking that sometimes it can take more than 6 months to fully dry out. 


  • Wipe with a dry cloth: Wipe the pane immediately with a dry cloth or towel to remove the condensed water droplets. It will ensure that the water does not sit on the surface. 
  • Improve air ventilation: The long-term solution involves improving air ventilation and circulation to reduce humidity levels. 
  • Maintain optimal indoor temperatures: Also, try to maintain the indoor temperatures at a constant level, possibly on a warmer side, to prevent surfaces from getting cold.
  • Use extractor fans: Extractor fans are recommended for bathroom and kitchen windows. They help remove moisture-laden air from the room, reducing humidity levels.
  • Cover pots and pans: When you cook, ensure that you cover all the pots and pans to reduce moisture. You can keep the windows open to remove moist air.
  • Tumble dry venting: When using a tumble dryer, place the vent pipe outside the window. 
  • Use dehumidifiers: Dehumidifiers are also recommended to keep indoor air dry, but this is a costly proposition. 

Double-glazed window condensation on the outside


Indoor-outdoor temperature contrast: This is not a common occurrence. However, water droplets can collect on the outside if the air outside is warmer and the glazed surface is colder. This occurs mostly during early mornings or late nights.


Double-glazed condensation on the outside is a sign that your windows are operating well and are energy-efficient, as they are meant to be. Thus, there’s no need to resolve any issue here. But, if you wish to lower the rate of condensation, you can do the following – 

  • Install Shades: Consider installing shades to reduce the chances of the window surfaces getting cooled so much that condensation happens. 
  • Plant Trees: Plant more trees or plants near the window to shelter it from condensation.

Double-glazed condensation in the Air Gaps 

Causes: Air gaps exist between the two glass panes in double-glazing units. This usually happens if the seals start to degrade. Thus, the condensed air gets inside the gap. This can result from:

  • Downgraded window components: aging, poor installation, broken or poor-quality seals. 
  • Faulty Spacer Bars: The spacer bar could also be faulty. Spacers contain desiccants that absorb moisture. However, if the spacer is not proper, the desiccant may not work optimally, and condensation starts to occur in the gaps.

Solutions: When condensation occur in gaps, it means that warm air is escaping from your home. In this case, there are two possible solutions: repair or replacement. 

  • Repair: If your uPVC units are in good shape, replacing the sealed units is a viable option. Specialized companies offer repair or reconditioning services by drilling into the ‘spacer’ bar or glass pane and injecting a drying agent or desiccant to eliminate condensation. They may also apply an anti-fogging agent to prevent future moisture accumulation. However, repairing may only address the immediate seal failure issue. Assess whether the benefits justify the cost and anticipated lifespan before committing to repairs.
  • Replacement: Replacement is costly, but it is also a great long-term solution. If your budget allows you to opt for this option, it’s recommended to speak with experts like Smart Home Improvement People who have the necessary experience to do the job effectively.

It is also recommended that you contact the window installation company and report the issue. If the window is still under warranty, they will replace it for free. While it is tempting to try to resolve the issues on your own, it is in your best interest not to do so. Companies like Smart Home Improvement People offer warranties on their replacement and repair services to keep it all stress-free for you.


Condensation in double glazing is a common challenge for UK homeowners, particularly during humid seasons like winter and autumn. Apart from its unsightly appearance, condensation can lead to mould growth on window sills and frames. This can potentially affect indoor air quality and health. It’s crucial to implement proactive measures discussed in this guide to address this issue effectively. These steps not only improve comfort but also extend the lifespan of your windows, promoting a healthier and more pleasant living environment. 

If you need double-glazed windows repair or replacement services, look no further. Talk to experts at Smart Home Improvements People today!

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