The short answer
Not by cleaning. If the cloud sits between the panes, the factory seal has failed and moisture is inside the unit, where no cloth can reach. The lasting cure is a new sealed glass unit, or a new rooflight if the frame is tired. Mist on the room side of the glass is different, and that kind does wipe and ventilate away.
- Free survey, fixed written quote
- 10-year workmanship guarantee
Which side is the mist on?
Press a dry finger to the glass on a cold morning and look at where the film sits. Beads or fog that smear under a finger are on the room face. That is condensation from the air in the room, and it points to humidity: a shower, a hob, laundry drying on the landing. A better extractor and an opened window will help it.
Fog that does not move, or a ghostly tide line and spotting that stays put, is inside the unit. It is a sign that the edge seal has opened, letting damp air in and any gas fill out. How the seal fails is set out under why rooflights mist up.
Three more clues help. A unit that is cloudy only at dawn is usually early in the process. A unit with a permanent grey haze, a dried tide line along the lower edge or small salt-like spots is further on. Condensation that comes back on exactly the same patch every morning, even after a wipe, is worth a look at the lining and the roof around it.
Why warmth and wiping do nothing
Heat does help for an afternoon. A unit that goes clear in the sun is drying out as the gap warms, then clouding again as the evening air cools it, which is the stage between a small leak and a full fail. Once the seal has gone, the unit takes in damp air every time it breathes with the temperature, and the staining that dries on the inside face of the glass can no longer be rubbed off.
Some people drill the outer pane and fit a small vent to dry the gap. The holes do not close the seal, and any gas fill that helped the unit's performance does not come back.
Keep a note of when the mist appears and how long it lasts. A unit that clouds each morning and clears by lunchtime is further along than one that shows a faint haze only in winter, and the pattern helps us judge whether the glass alone needs swapping or the whole frame has aged too.
| Where you see it | What it means | What removes it |
|---|---|---|
| On the room face of the glass | Humid air meeting a cold surface | Ventilation and a drier room |
| On the lining or reveal | Cold edge or poor ventilation | Better airflow; we look at the lining |
| Between the panes | Failed edge seal | A new sealed unit or a new rooflight |
| Dripping, or a wet stain on the ceiling | Water getting past the flashing or the kerb | Found by a roof inspection first |
What actually clears it
A new sealed unit goes into the existing frame when the frame is square, sound and the right depth. The old glass comes out, the new one is bedded and the room is back to a clear view of the sky. On a pitched roof the roof window sash can sometimes be reglazed with the lining kept. When the frame is cracked, warped or too thin for current glass, the whole rooflight is the better answer, and glass only or whole unit sets out how that choice is made.
We measure the old unit for width, height and glass thickness, and read the code or label on the frame if there is one. For a roof window the letters in a code such as MK04 give the width and the digits the height. Then the new unit is made to those sizes. A conservatory or orangery roof with several glazed panels is handled panel by panel, and the survey tells us whether the bars and the gaskets around the panels are fit to reuse.
What you can ask the new glass to do
A replacement unit does not have to copy the old one. A low-emissivity coating helps the room hold its heat, a warm-edge spacer keeps the rim of the glass warmer, a laminated inner pane stays together if it cracks, and solar control glass suits a south or west slope. A new roof window must meet the window limit of 1.4 W/m²K, or Window Energy Rating band B; a rooflight or lantern the limit of 2.2 W/m²K. We note the figure on your quote.
If water has been coming in, as well as mist, read whether a misted skylight leaks. For how long a good unit should last, there is how long rooflights last.
Getting a replacement priced
Send a clear picture of the glass and any label on the frame to WhatsApp 07880 284133, or email info@orchardskylightsmaidstone.co.uk. We then arrange a free survey and give a fixed written quote, with the Building Control notification handled where the work is notifiable. The work carries our 10-year workmanship guarantee in writing. For the full picture, see misted rooflights, or book a survey.
