Why Is Condensation Forming on the Inside of My VELUX Roof Window?

Finding water droplets on the inside of your VELUX roof window can be worrying, particularly if you notice moisture collecting on the glass or dripping onto the sill. However, this does not always mean your roof window is leaking. In many situations, the moisture is caused by condensation, which occurs when warm, humid indoor air comes into contact with a colder glass surface.

Understanding Why Condensation Happens

Everyday activities can create significant amounts of moisture inside your home. Cooking, showering, bathing and drying clothes indoors all release water vapour into the air. If this humid air cannot circulate and escape properly, it can settle on colder surfaces, including roof window glazing.

The problem can become more noticeable during colder months when outside temperatures fall. Older or single-glazed roof windows may be particularly susceptible because their internal glass surface can become much colder than modern energy-efficient glazing.

How Can You Tell Condensation from a Leak?

It is important to establish whether the moisture is condensation or water entering from outside, as each problem requires a different solution.

Condensation generally forms directly on the room-facing side of the glass. It may be more noticeable in the morning and can reduce when heating, ventilation or an extractor fan is used.

A genuine leak is more likely to leave watermarks or staining around the frame, ceiling or surrounding plaster. It may become worse following heavy rain and can continue even after the room has been ventilated. If you notice damp patches around the roof window rather than simply on the glass, an inspection is advisable.

When Everyday Ventilation Doesn't Solve the Problem

Improving ventilation can make a considerable difference to normal household condensation. Opening windows periodically, using extractor fans and maintaining consistent airflow can all help reduce excess humidity.

However, persistent condensation may indicate that the roof window itself is reaching the end of its useful life. Damaged glazing seals, deteriorated components, inadequate insulation or an older window design can all contribute to excessive moisture and heat loss.

Is It Time to Consider Replacement?

If your roof window is more than 15 or 20 years old, has visible deterioration, develops mould around the frame or regularly suffers from condensation, replacement may be worth considering.

A Velux Roof Window Replacement can provide an opportunity to upgrade to modern glazing with improved thermal performance and sealing. A newer unit can help maintain a more comfortable indoor temperature while reducing the likelihood of cold internal glass surfaces where condensation forms.

Rather than repeatedly cleaning mould, repairing damaged finishes or dealing with recurring moisture, replacing an ageing roof window may offer a more practical long-term solution.

Making Sure the Replacement Is Installed Correctly

Replacing the window itself is only part of the process. Correct installation of the insulation, vapour barrier and flashing is essential for protecting the opening against heat loss, moisture and weather penetration.

Yorkshire Roof Windows specialises in VELUX roof window replacements and aims to complete suitable replacement work from inside the property where possible. This can help minimise disruption while ensuring the new installation is properly sealed and weather-tight.

If your roof window is regularly covered in condensation, don't automatically assume you have a leaking roof. An assessment can help identify whether better ventilation, a repair or a complete replacement is the most suitable option for your property.