Self-cleaning glass
Is self-cleaning glass worth it on a conservatory roof?
The short answer
Sometimes. Self-cleaning glass has a coating that helps break down light dirt in daylight and lets rain rinse it away, so it can cut how often you wash the roof. It does not deal with bird droppings, tree sap, moss on the frames or dirt on the inside, and it needs rain to work. It suits open, sunny roofs more than shaded ones under trees.
What the coating does, where it stops working, and a simple way to decide whether it is worth paying for on your own conservatory roof.
What the coating does
Self-cleaning glass has a very thin coating on the outer face of the outer pane. In daylight the coating reacts with the dirt that has settled on it and starts to loosen it. It also makes water spread out in a thin film instead of forming beads, so when it rains the water sheets across the glass and carries the loosened dirt away with it. Two things have to happen together: daylight and rain.
The coating is designed for the sort of dirt that blows onto a roof, such as dust, traffic film and pollen. It works best on a roof with a decent slope, because the water has to run off the glass in a sheet. On a low-pitched glass roof the water stands longer and the dirt can dry in place. The effect is gradual, too. Glass that has been dirty for years will not look new after one shower, and the first few weeks after fitting are not the point at which to judge how well it works.
Where it falls short
The coating cannot shift everything. Bird droppings dry hard and stay put. Tree sap, honeydew from aphids and the green film that grows where shade keeps the glass damp all sit on top of the coating and need washing off. Moss and algae collect at the bars and in the gutter, not on the glass, so the frame still needs attention. The inside face of the roof is untouched, and condensation, cooking film and dust gather there as they would on any glass.
A long dry spell is another limit. With no rain the glass cannot rinse itself, and with dry, sunny weather dirt can bake on. That is common on a coastal south-facing roof in summer, where sea haze and dust settle for weeks between showers. You may still need to rinse the roof with a hose in those spells, which defeats part of the saving. It reduces the work. It does not remove it.
When it earns its place
The coating pays off most where the roof is hard to reach. A conservatory under a tall house wall, a roof above a bay, or one with an awkward flat section that needs a ladder and a long brush each time, will see the biggest benefit from anything that cuts the number of cleans. It also suits open gardens, where the roof gets full daylight and plenty of rain, and homeowners who would rather not climb at all.
It is worth less under an overhanging tree, beside a hedge, or in a corner that stays damp, where the dirt that builds up is exactly the sort the coating cannot handle. If your roof is that kind of site, the better spend may be a regular clean. Our page on which glass is best for a conservatory roof puts the coating alongside the other options, such as solar-control layers, so you can see where it ranks for your room.
Cleaning it the right way
Even with the coating, an occasional wash helps. Use plenty of clean water and a soft brush or sponge on a pole. Keep to mild, non-abrasive cleaners recommended for coated glass, because harsh products, scrapers and abrasive pads can mark or damage the finish. Rinse well so no film is left behind. Choose a dull day if you can, since in strong sun the cleaner dries in streaks before you rinse it.
Never walk on a conservatory roof, glass or otherwise. It is fragile, and a ladder resting on the panes can crack them. Use a pole from the ground, a proper access tower or a cleaning specialist with the right equipment. Our guide to conservatory roof cleaning covers how the job is done, and the moss and algae on frames and in gutters is handled the same way as on any other roof. If the roof is near the end of its life, the coating becomes part of a bigger choice, set out under conservatory roof replacement.
Deciding whether to pay for it
The coating adds a premium to the glass, and the amount depends on the unit and the supplier, so there is no fixed figure to quote here. What you pay is fixed by the quote that follows the survey. Weigh it against how much you dislike cleaning, how shaded the roof is and how steep the pitch is. A steep, open roof that is awkward to reach is a good candidate. A shaded, shallow roof that you can reach from a pole may not repay the extra.
If you are replacing the whole roof, the coating is easiest to specify at that stage, because adding it later means replacing the glass. If you are replacing only one damaged unit, it is worth asking for the same coating, so the new pane does not stand out against the old ones. Our guide to replacing a conservatory roof panel explains how a single unit is matched.
Related questions
Self-cleaning roof glass
Does self-cleaning glass work in a dry summer?
Less well. The coating needs rain to rinse away the loosened dirt, so long dry spells leave marks that a hose will have to deal with. The glass stays easier to clean than uncoated glass.
Can I add the coating to glass I already have?
The factory puts the coating on during manufacture, so it cannot be added to a fitted unit. If you want it on your roof, the unit has to be replaced with a coated one.