Can rooflight glass stop furniture fading?

Fading is a chemical change. Sunlight carries enough energy to break the bonds in dyes and pigments, and in the lignin that gives timber its colour. Three parts of the light do the damage.

Ultraviolet is the most energetic band, and it is the most damaging per unit of energy. Visible light, especially the blue end, does real harm too. Infrared adds warmth, and warmth speeds up the reactions already under way. No single band is solely to blame, which is why any claim that a pane of glass "stops fading" is an overstatement. Take out one band and you slow the process, but the other two carry on.

A rooflight makes the problem sharper than a wall window. It faces the sky, so it collects light for more of the day, and the sun is often high enough to pour straight down onto one patch of floor. A rug or a pale oak board beneath an unshaded rooflight can show a sharp-edged bleached square over the years. A sofa under a loft window with a southern aspect is another usual casualty.

Where you live adds little. Sussex is not a sunnier county than its neighbours. What changes the outcome is the direction the glass faces, how big it is, and how long the sun sits on the same spot. Our page on choosing rooflights by orientation goes through each aspect.

The glazing build does the most for ultraviolet, and the layer that does it is one we specify for another reason.

A laminated pane is two sheets of glass bonded around a plastic interlayer. The interlayer absorbs a large share of the ultraviolet passing through, well beyond what a plain sheet of glass does. We choose a laminated inner pane for overhead safety, and the acoustic version for quiet, because the interlayer damps vibration. The ultraviolet benefit comes along with it. Our answer on one glazing build for warmth and quiet shows how the pieces fit together, and the question of quiet is in our quiet spec.

Plain toughened glass with no laminate lets more ultraviolet through. It is a perfectly good glass for strength and is still fitted in rooflight units, but it offers no ultraviolet advantage. If fading is a worry, ask for the unit's ultraviolet transmission figure from the manufacturer's published data, and do not accept a general reassurance. Data sheets sometimes list it, and if a sheet is silent, ask the supplier.

A coating helps with the infrared, and it takes a further bite out of the ultraviolet. It does little about the visible light, and that is why it is not a fading cure on its own.

Solar control coatings are designed to turn back part of the sun's heat while keeping the room bright. Because the infrared is reduced, the warmth that speeds fading is reduced too. Some coatings also trim a little ultraviolet and a little visible light as a side effect. The effect is modest, and a bright south-facing room will still age what is in it. Read about how the coating works on our page on solar control glass for rooflights, and about the brightness trade in whether solar control glass makes a room darker.

Tinted glass reduces more visible light, and therefore more of that part of the fading. It also darkens the room, which is the price. For a living room you want bright, a neutral coating over a laminated inner pane is usually the better balance than a dark tint.

Glass sets the baseline. The last stretch of protection comes from what you do inside the room, and some of it costs nothing.

A blind is the single most effective measure, since it stops the light before it reaches the floor. A light-filtering blind on a rooflight keeps the room bright while cutting the direct beam, and a blackout type protects a spare room that is rarely used in daylight. Our page on stopping a rooflight room from overheating covers blinds from the heat side, and the same blind does both jobs.

Some simple habits help too. Move a rug every season so that no strip takes the full beam. Keep timber floors that you care about under a runner where the sun lands. Where you are choosing a new opening, size and position matter: a modest rooflight set toward the back of a room will paint a smaller patch of light on the floor than a wide one overhead. We weigh these when we position the unit at the survey.

Will my existing rooflight fade things faster if it is old?

It depends on its glass. An old single pane or a plain double unit passes more ultraviolet than a modern laminated one. A failed seal adds no extra fading, though it may add misting. Our page on upgrading an old rooflight covers the options.

Does a north-facing rooflight fade anything?

Much more slowly, because it rarely takes direct sun. Diffuse daylight still contains ultraviolet, so a pale fabric left for years will eventually change.

Is low-E glass the same as solar control glass?

They are related coatings with different aims. Low-E is about keeping warmth in during winter, and solar control is about keeping heat out in summer. Our page on low-E coatings on rooflight glass explains the difference, and a single unit can carry both.

Does the g-value tell me how much it will fade?

Only in part. The g-value measures total solar energy passing through, which includes heat. It does not isolate ultraviolet. See what a g-value is for how to read it.

If there is a floor or a sofa you want to protect, get a quote and tell us which part of the room the sun reaches. We will write the glazing build into your quote, and the full service is on our energy efficient rooflights page.