Can Misted Skylight Glass Be Cleared?

When a skylight misted rooflight has fogged, the cloud sits in the gap between the panes. Both outer faces can be spotless and the haze will remain. The gap is closed off on purpose, so a cloth, a squeegee or a window cleaner cannot reach it.

Mineral marks make it harder still. Each time moisture condenses and dries, it leaves a thin residue on the inside faces. Over time this builds into a dull film and tide lines. These do not shift with any household product, however strong.

Ordinary condensation on the face you can touch is different, and it does wipe away. If a cloth clears it, you have steam or a damp room, not a failed unit. Our answer on what causes the cloud between the panes covers how to tell the two apart.

Demisting rooflight glass is a method where small holes are drilled in the unit, the trapped moisture is drawn out, and the holes are sealed or fitted with a vent. The idea is to leave the original glass in place, and the pane can look clearer afterwards.

The limits are worth knowing before you choose it. A sealed unit works because it keeps out moist air and holds an insulating fill. Drilling it breaks that seal. A vent lets air move in and out, so the fill is lost, and moisture can return. The insulating performance of the glass will not be what a new unit gives, and a rooflight has to meet a fixed heat-loss limit when it is replaced.

Mineral marks that have already formed are not always removed either. A treated pane can be clearer without being clean. As a firm that installs and replaces rooflights, our recommendation is a new sealed unit, and we say so plainly at the survey.

A new sealed unit gives you clear glass, a fresh seal and a modern specification. It is measured from the unit in your roof, made to that size and fitted in place of the failed one. In many openings the frame and flashings stay exactly where they are, and the work is quick and contained.

The frame has to earn its place. If the timber is sound, the metal uncorroded, the flashings tight and the lining dry, new glass in the old frame is a sensible route. If not, a whole new rooflight lasts longer. The decision is set out in full in our guide to new glazing or a new rooflight.

Either way the finished opening has to meet Part L. Table 4.2 of Approved Document L (2021) is the place to look, and it gives a separate limit for rooflights and for roof windows. Our fitting follows current Building Regulations, with Building Control told where required.

If someone offers to clear the glass, a few plain questions help. Does the treatment replace the seal, or only drill through it? Is the gas fill restored? Will the pane meet the current heat-loss limit if it is ever assessed? What happens if the fog returns? A straight answer to each tells you what you are buying.

It also helps to think about the spot beneath the rooflight. A pane over a landing or a store cupboard may not matter much to you, while a pane above a kitchen worktop or a reading chair matters every day. How much the clarity is worth to you is a fair thing to weigh, and the survey lets you see the choice laid out with the room in mind.

Think about the age of the rest of the unit too. Misting often arrives when the frame and flashings are also getting old. Fitting new glass into a frame that is close to the end of its life is poor value, and it is better to know that now than after the work. That is why the survey looks at the whole opening and not only the pane.

Finally, ask for everything in writing. A fixed written quote shows what is being fitted, to what specification, and with what guarantee behind it. Ours comes with a 10-year workmanship guarantee in writing.

The quickest way to settle it is a free survey. First comes a look at the room, where you want the light and the roof, then the unit is measured and the frame inspected. Nothing is priced until that is done.

A fixed written quote follows, with the figure agreed before work starts. Our workmanship guarantee runs for 10 years, in writing.

Use the free survey form, or WhatsApp a photo to 07880 284133. Our hub page on misted rooflight replacement covers the rest.