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Condensation is one of the most common (and misunderstood) issues homeowners face during colder months. Whether it’s early morning misting or persistent moisture, condensation can lead to mould, damage timber sash window frames, and ruin the look and performance of your windows. But when is it a problem – and when is it actually a sign that your windows are working properly?
Condensation on the outside of your windows typically forms when the outer pane is colder than the surrounding air – often on clear, humid mornings. This usually occurs in highly energy-efficient double or triple-glazed windows, where heat retention is so effective that the outer pane stays cool, allowing moisture in the air to settle.
In these cases, external condensation is a sign your windows are performing well, creating a thermal barrier that keeps your home insulated.
Internal condensation, on the other hand, occurs when humid indoor air meets a cold glass surface. This is especially common in winter when our homes are sealed tight to keep in warmth. Everyday activities like cooking, showering, drying laundry, and even breathing add litres of moisture to the air. Without proper ventilation, this excess humidity settles on cold surfaces – especially windows.
Many people believe that double-glazing eliminates condensation entirely. It doesn’t. In fact, modern airtight homes can actually trap more moisture inside, especially if ventilation is poor. Double glazing helps reduce heat loss, but it also reduces airflow, meaning moisture has fewer escape routes. That’s why condensation can appear even on brand-new windows.
Here are proven strategies to minimise condensation inside your home during colder months:
• Ventilate Strategically: Open windows for 5–15 minutes a day, ideally after activities that release moisture like cooking or showering. Cross-ventilation (windows on opposite sides of the home) is most effective.
• Use Trickle Vents: Ensure trickle vents on your windows are open to allow for constant airflow.
• Run Extractor Fans: Especially in kitchens and bathrooms—use them during and after steamy activities.
• Control Humidity: Dehumidifiers are highly effective. Choose a smart, quiet model for bedrooms or living areas and run it during peak moisture times.
• Avoid Drying Laundry Indoors: When possible, use vented tumble dryers or dry clothes outside.
• Use Passive Moisture Traps: These low-cost containers help in areas like under sinks, behind furniture, or inside cupboards.
• Keep a Consistent Temperature: A moderately heated home helps reduce temperature differences on glass surfaces, minimising condensation risk.
Yes – briefly. A quick burst of ventilation helps clear out humid air without significantly impacting indoor temperature. Even 10 minutes of fresh air exchange can make a difference.
Cold glass attracts moisture, so insulating windows is key. Use thermal curtains or blinds, window insulation film, and ensure frames are sealed with weather stripping or silicone caulk. Keeping window surfaces slightly warmer reduces condensation build-up.
• Bedrooms: Ventilate every morning. Avoid placing beds against exterior walls. Use a small dehumidifier at night if needed.
• Kitchens: Always cook with lids on pots and use extractor fans. Crack a window open while cooking to release steam.
• Bathrooms: Keep extractor fans running for at least 20 minutes post-shower. Open windows to release humidity. Keep the door closed to prevent steam from spreading.
While most condensation is harmless, persistent or excessive moisture can lead to mould, peeling paint, and even rotting window frames. If you see:
• Black mould around the frames
• Moisture between panes in double-glazed units
• Timber starting to warp or deteriorate
It may be time to seek professional help. These are signs of a deeper issue—such as failed seals or poor insulation.
At Todi & Boys Joinery, we’ve spent over 30 years working with London homeowners, heritage properties, and conservation-area homes. We specialise in timber sash and casement windows—restoration, replacement, and modern upgrades with double-glazing, draught-proofing, and expert craftsmanship. If you’re struggling with condensation or simply want to future-proof your property with high-performance traditional windows, we’re here to help.
Condensation might seem like a minor issue, but left untreated it can cause major damage. Understanding when it’s normal (like on the outside of well-insulated glass) and when it’s a warning sign is crucial. With the right approach—ventilation, insulation, and moisture control—you can maintain a warm, dry, and healthy home throughout winter. And when it comes to premium timber windows, trust experts like Todi & Boys to guide you to the best long-term solution.
Get in touch today for tailored advice, expert restoration, or to upgrade your home with high-performance sash and casement windows that look beautiful and work even better.
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