Short answer
A misted rooflight is a fault in the glass unit, not a leak. Moisture between the panes means the sealed gap is no longer sealed, and no amount of wiping will reach it. Mist by itself says nothing about the roof, but a stain on the ceiling or lining would, so the weathering around the glass gets checked too.
Free survey / fixed written quote / Building Control notification handled / 10-year workmanship guarantee
More than a cosmetic grumble
A haze inside a rooflight is easy to shrug off, because the window still lets light through and the room still has a ceiling. A loft bedroom, a landing or a hallway all carry on as normal, which is how a failed unit can sit unnoticed. What the haze tells you is mechanical. A double-glazed unit is two panes with a closed gap between them, and a triple-glazed one has three. That gap is built to stay shut against both the room and the weather. Moisture inside it means the seal has given way.
So the answer to "just ugly?" is that the glass has failed at the one thing it was assembled to do, and a cloth cannot reach it. The mist can be faint for a while. Low sun after a wet week shows it up, where a flat grey sky would hide it, so a bright morning can be when it first shows.
Checking it really is the sealed unit
Cloudy glass can have more than one cause, and only one of them is a sealed-unit failure. Fog on a bathroom roof window after a shower is warm, wet air meeting a cold pane. It sits on the room face and goes when the room settles. A landing rooflight that looks dull from the garden may be wearing a film of dried rain and grime. Neither is a sealed-unit problem, and a few minutes of checking will sort out which cloud you have.
Three quick checks
- Wipe the room side If the cloud wipes away, it was steam, and the room needs air moving through it.
- Look at the outside face A dull, even film that cleans off is dirt, and a coating can slow its return.
- Look between the panes A haze or droplets that stay put after both wipes sit inside the sealed unit.
When the damp is somewhere else
Mist and leaks are different faults that can live in the same roof. A leak is rain finding its way past the weathering around the glass, and it shows as a stain or soft patch on the ceiling, on the lining beside the window or on the inner edge of the frame. Mist in the glass does not cause that, so a stain means the roof around the unit needs attention too.
On a flat roof, the telltale is water left standing against the kerb long after a shower has stopped. That points at the fall and the outlet. On a pitched roof the weathering is the flashing that laps the tiles or slates around the window.
Our survey takes in the glass and the weathering in a single visit, because a unit that has misted can sit on a roof that has other things to say. Our guide on why rooflights mist between the panes covers the cause of the glass fault itself.
What fixing it involves
There are two ways to put it right. The sealed unit can be swapped while the frame, kerb and flashing stay in place, or the whole rooflight can be replaced. A frame that is square and tight suits the first. The guide on swapping the glass unit or the entire rooflight sets out how that call is made.
The rules follow the job. Swapping only the glass, with the existing frame left alone, falls outside the energy rules. A whole replacement roof window should reach 1.4 W/m²K or Window Energy Rating band B in Wales, and a replacement rooflight 2.2 W/m²K, under Approved Document L. Where the work is notifiable, we handle the Building Regulations notification with local authority building control or a registered building control approver.
Since the price follows the job, the answer on misted rooflight glass cost lists the things that push it up or down.
Before you ring
A few details shorten the first conversation. Tell us the room under the glass, whether the roof over it is flat or pitched, whether the window opens and whether it works by hand or by motor. Mention any damp nearby too. None of that needs a ladder.
Then comes a free survey and a fixed written quote, and our workmanship carries a written 10-year guarantee. Ring 01792 929062 or send the survey form, and see misted rooflights for the full range of the service.