Lifespan answer
How long does a VELUX window last?
There is no single figure, because a roof window is several parts that age at different rates. Seals and flashings tend to give up before the frame does.
The answer
A well-fitted VELUX frame can outlast several sets of seals, but there is no honest single number. The glazing seal and the flashing around the window usually show age first, and the roof it sits in sets the pace. A window is due for replacement when the glass has misted, the sash no longer closes squarely, or the join with the roof has stopped keeping water out.
Which part of a roof window wears out first?
The sealed glazing unit and the flashing around the frame tend to go before the frame, because they take the weather and the temperature swings.
A roof window works hard. It faces the sky, takes rain and sun on one side and room warmth on the other, and its seals flex with every change of temperature.
The glazing seal
Double glazing is two panes with a sealed gap between them. Over time the seal can fail, letting moist air into the gap. The first sign is a hazy film or droplets between the panes that cannot be wiped away. The reasons behind it are covered in a guide to why rooflights mist up.
The flashing and collars
The metal and the underlay round the frame are fixed to a roof that moves slightly as it warms and cools. The join between metal and covering is the first place a long-term problem shows up, even when the window itself is fine.
Moving parts
Hinges, springs and handles wear with use. A window opened daily for ventilation will show it before one that is opened twice a year.
The frame
The frame is the slowest part to age. Timber frames, treated and finished at the factory, last well when kept dry. That is why a swap of the glazing alone is sometimes a sensible choice, as weighed up in our page on replacing in the same opening.
What makes a window age faster?
Exposure, damp rooms, poor fitting and a covering that has moved. The same window can age at very different rates in different roofs.
Two identical windows can end up in very different condition after the same time. The difference is almost always the setting.
Exposure
A roof that takes the full force of wind and rain, or sits in strong afternoon sun, loads the seals and the paint more than a sheltered slope. We judge exposure by looking at the slope itself, not a map.
Damp rooms
A bathroom or a kitchen puts more moisture against the glass than a bedroom. If the room is poorly ventilated, condensation sits on the lining and the frame for long periods, and wood and paint suffer.
How it was fitted
A poorly sealed collar, a flashing laid for a different covering or a window out of square in its opening ages quickly. Workmanship has a large say in how long a window lasts. Our installation sits under a written 10-year guarantee, described on the guarantee page.
The roof around it
If slates slip or tiles crack around the window, water can reach the join from above and it will not matter how sound the window is.
How do I know when to replace it?
Misting between the panes, a sash that will not close squarely, staining on the lining and cold air at the frame are the usual signs.
A window rarely fails all at once. It gives hints first, and the hints are easier to read if you know where to look.
Inside
Look at the lining and the ceiling nearby. Brown stains, flaking paint or soft plaster point to water finding its way in. Mould in the corners can mean condensation, a gap in the insulation collar, or both.
On the glass
Haze or droplets between the panes mean the seal has failed. The window still keeps the rain out, but the insulation is reduced and the view is spoilt.
In use
A sash that sticks, drops or will not stay open has a hinge or spring issue. A draught around the closed sash points to worn seals.
The list gives the usual signs to look for.
Signs worth acting on
- Haze or droplets trapped between the two panes of glass.
- Brown stains or soft plaster on the lining below the window.
- A sash that sticks, sags or no longer sits square.
- A cold draught around the frame when the window is shut.
- Slipped slates or tiles around the flashing on the outside.
Is an old window worth keeping?
If it is dry, square and clear, keep it. If the glass has failed or heat is escaping, a new window meets today's Part L standard and brings its flashing with it.
A window that has done its time is not always a problem. If the glass is clear, the sash closes, and the lining is dry, it can carry on.
Why a newer unit can be better
Glazing has improved over the decades. A new roof window for an existing dwelling must meet a limiting U-value of 1.4 W/m²K, or WER Band B, and an older unit may fall short of that. Our page on rooflight U-values explains what the figure means.
Replace or fit new
If you decide to go ahead, we survey first, then give a fixed written quote. The survey reads the frame, the glazing, the lining and the covering together, so you hear whether a swap of glass would do or the whole unit should go. For an upstairs or downstairs Tyneside flat, the roof can be shared, which is why your lease or title should be read for the other owner's say before an order. Look at the VELUX windows page for the full picture.
Lifespan questions we hear
Does the guarantee match the life of the window?
No. The workmanship guarantee is for the installation, runs 10 years and is in writing. It is not a forecast of how long the window itself will last.
Can only the glass be changed?
Sometimes, when the frame is sound and the sash is square. The survey checks both, and the quote says which route suits your window.
Does a north-facing slope age differently?
The weather load differs by slope, but the setting and the fitting matter more than the compass. We read each roof on the day of the survey.
Is a misted window dangerous?
It is not a safety issue by itself. The seal has failed and the insulation is reduced. Our page on misted rooflights covers what to do next.