Condensation and foggy windows

  • 8th January 2024
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Fixing Window Condensation

Windows allow the outside world in, but sometimes they bring condensation. Condensation between the panes is also quite common. So, if you ever wondered why your windows become misty or foggy, here we look at what causes it and what you can do about it.

How Does Condensation Happen?

Condensation happens when warm, moisture-laden air meets a cooler surface, like a window. This meeting prompts water vapour in the air to transform into droplets on the glass. While it's a natural occurrence, getting regular condensation often means issues with ventilation, indoor humidity or window quality. Checking ventilation and humidity levels and evaluating window repairs will help you begin to find the solution.

Health Issues

Having condensation can lead to health issues such as breathing problems and allergies too. To deal with window condensation properly, you’ll need to identify the cause of the problem.

Areas of damp and moisture in the home are the perfect conditions for mould spores and bacteria to multiply. Mould is now considered to cause asthma to develop, not just make it worse. These pollutants can cause a range of other health problems too:

  • Runny nose
  • Sore throat
  • Rhinitis
  • Sinusitis
  • Allergic bronchopulmonary aspergillosis – this is when a person has an allergic and inflammatory reaction to mould spores
Fixing Condensation

There is a range of strategies available based on the severity of the issue. Simple DIY fixes, like improving ventilation by using extractor fans or regularly opening windows can make a difference. There are also more advanced solutions like installing permanent dehumidifiers or even considering window replacements for better insulation.

But prevention is better. Preventing window condensation is as important as fixing it.

Maintaining good indoor humidity levels, using proper ventilation and investing in better windows, if needed, can significantly reduce the problems of condensation.

Prevention is Key

While fixing window condensation is essential, preventing its recurrence is just as important.

  • Maintain Balanced Indoor Humidity: Keeping indoor humidity levels in check is fundamental. Invest in a hygrometer to monitor humidity; ideally, maintain levels between 30% to 50%. If humidity surpasses these levels, consider using a dehumidifier to regulate it.
  • Improve Ventilation: Proper ventilation is vital in reducing condensation. Make sure your home has adequate airflow by using extractor fans in kitchens and bathrooms. Opening windows periodically, especially during activities that create moisture such as cooking and showering, allows fresh air to circulate, helping to reduce condensation buildup.
  • Upgrade to Energy-Efficient Windows: Consider upgrading to energy-efficient windows with multiple panes or low-emissivity coatings. These windows provide better insulation and reduce the likelihood of temperature differences that cause condensation.
  • Insulate and Seal: Properly insulating windows reduces the temperature variations that lead to condensation. Check for gaps or leaks around window frames and seal them using weather stripping or caulking to maintain consistent indoor temperatures. Call an expert if you’re unsure.
  • Control Moisture Sources: Minimise sources of indoor moisture. Cover pots while cooking, dry clothes outdoors whenever possible, and ensure any vents are clear of debris and properly directed outside to prevent moisture buildup indoors. Simple fixes like improving ventilation, using dehumidifiers, or adjusting indoor humidity levels might help reduce condensation in certain cases.

Sometimes, condensation can build up between the panes of double or triple-glazed windows. It can be a frustrating issue. When moisture appears between the panes, it typically indicates a problem with the window's seal, allowing moisture to enter and become trapped between the glass layers.

Condensation Between Panes

When the seal that keeps the space between the glass airtight fails, moisture can penetrate. This moisture accumulation not only means the insulation capacity of the window has been compromised, but it also obstructs your view.

Causes of Seal Failure

There are several things that can lead to a failed seal:

  • Age and Wear: Over time, the window's seals can degrade due to exposure to weather elements, temperature fluctuations and general wear and tear.
  • Poor Installation: Incorrect installation or manufacturing defects can compromise the seals, leading to premature failure.
  • Extreme Weather Conditions: Drastic temperature changes, especially in regions with significant climate variations can stress the seals, causing them to break.
Addressing Condensation Between Panes

Unfortunately, once condensation appears between the panes, the only permanent solution is often to replace the affected insulated glass unit. This involves replacing the entire sealed unit, which includes removing the old glass and installing a new, properly sealed one.

For this, you’ll need a reputable glazier or window specialist. They can assess the extent of the damage, determine the best course of action and replace the affected window unit professionally. Attempting to fix or replace the unit without proper knowledge can lead to an unresolved problem and further damage to the window.

Preventing Fogging Issues

Addressing foggy windows or condensation between the panes isn't considered an easy fix, especially if the issue involves insulated glass units:


  • Replacement: The most effective solution often involves replacing the affected insulated glass unit. This process requires professional expertise and involves removing the old glass unit and installing a new one with proper sealing.
  • Professional Assistance: Attempting a DIY fix for condensation between panes can lead to further damage or an ineffective resolution. Professional glaziers or window specialists have the expertise and tools required to replace these units properly.
  • Cost Consideration: The cost of replacing insulated glass units can vary based on factors such as the size of the window, type of glass, and labour involved. It's crucial to weigh this cost against the benefits of having clear, properly functioning windows.
Final Thoughts

While addressing foggy windows due to seal failures between panes may not be an easy or quick fix, tackling condensation caused by interior factors might be more manageable with some adjustments to your home's environment.

But you’ll need to consider seeking professional advice or assistance, especially when dealing with issues related to insulated glass units.

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