The answer
Replace a VELUX window when it lets in water, stays misted between the panes, will not open or close properly, or feels cold and draughty. There is no fixed lifespan, because a unit's life depends on its sun, weather and glass. A survey tells you whether one part or the whole window has reached the end.
Misting between the panes
A VELUX window is double glazed, with a sealed gap between two sheets of glass. When that seal fails, damp air gets in and the glass clouds from the inside. No amount of wiping reaches it, because the moisture sits inside the unit.
Misting is the clearest sign that a sealed unit has done its work. It also means lost insulation, since the gap no longer holds what it was built to hold. A skylight should be the brightest thing in the room, and a clouded one gives back less of the sky. Our guide to replacing a VELUX window shows what the swap involves, and the VELUX windows hub gives the wider picture.
Water marks, stains and soft ceilings
A brown ring on the ceiling beside the window, bubbling paint or a damp patch after heavy rain all point to water getting past the window or the flashing around it. Sometimes the fault is only the flashing, the metal that dresses the window into the roof covering. Sometimes the frame itself has let go.
Do not leave a stain to dry and forget it. Water that finds its way in once will find the same route again, and timber around a roof opening does not forgive months of damp. A survey separates a flashing problem from a failed frame, so you replace only what has to go.
A window that sticks, jams or will not stay shut
A roof window should swing or pivot with one hand and close with a firm, even seal. If the sash drags, the handle needs force or the window drifts open, the hinges, the seals or the frame may have moved. Gaps along the edge let in draughts and noise, and a window that cannot close tightly cannot keep rain out in a gale.
If you have an electric or solar opening model, a motor that stalls, a remote that no longer answers or a rain sensor that has stopped working can also point towards a new unit. Newer controls are a worthwhile gain when the old window is coming out anyway, and a fitted blind can be chosen at the same time.
Cold glass, draughts and old specifications
Glass made some time ago does not match what is on offer now. If the pane feels cold on a winter morning, if condensation runs down the inside, or if the room is hard to heat under the window, the unit may simply be out of date. Current replacements carry better coatings and seals and meet the energy figures set for existing homes.
Those figures come from Part L of the Building Regulations. For a roof window, Approved Document L (Table 4.2) sets a U-value of 1.4 W/m²K, and a Window Energy Rating in band B also meets it. A rooflight in the flat roof of an extension has its own, separate limit. Our size code guide helps you read the label on your frame before you order anything.
What a new unit is measured against
- 1.4 W/m²K
- ceiling for a replacement roof window, or WER band B
- 2.2 W/m²K
- most heat a flat rooflight may lose in an existing home
How long does a VELUX window last?
There is no honest single number. A window in a shaded north slope lives a quieter life than one on a south-facing roof taking strong sun and driving rain all day. Coastal air, tree cover, how often the window is opened and the quality of the original fitting all play a part. Plastic and rubber parts weather in sunlight, and a pale frame that has turned brittle or discoloured is telling you something.
What you can do is watch for the signs above. The seal, the frame, the flashing and the glass can fail at different times, and a survey takes a few minutes of looking from inside and out. Nothing is charged for the visit, and the figure we give afterwards is written down and stays put.
A short check before you call
Run through these at home and note what you find. They make the survey quicker and the advice more exact.
Before you book
- Is there mist or a watermark between the panes?
- Is there a stain on the ceiling or reveal beside the window?
- Does the sash open, close and latch cleanly?
- Can you read the size code on the label inside the frame?
- Is the room too cold or too warm under the glass?
What happens once you decide
Next comes the free survey, where the opening is measured, the code is read and the covering round the window is checked. The quote that follows is written down and holds firm when we arrive. The new window goes in to current Building Regulations. Where the work has to be notified, Building Control hears from us, not from you. The lining is finished and the room left tidy, and a 10-year workmanship guarantee comes in writing.
A photo of the window and its label, sent to WhatsApp 07880 284133 or emailed to info@vertexskylightsmiltonkeynes.co.uk, gives us a first view before we visit.
Related questions
Should I replace just the flashing or the whole window?
Look at the glass and the frame first. If the unit is clear, sound and opens well, a new flashing set may be all that the roof needs. If the glass is misted or the frame has gone soft, replacing the window and the flashing together saves doing the job twice. We will tell you which applies at the survey.
Will a new window be the same size as the old one?
It can be. A like for like swap fits the existing opening, and the size code tells you what to order. If you want more glass, read about making a VELUX window bigger.
How long does the swap take?
The fitting is quick compared with the wait for a window to be made. The answer is set out in how long a VELUX installation takes.
