Self Cleaning Glass and Rooflights

Few people actually enjoy the task of cleaning their windows, especially if there are a lot of them. However, when it comes to rooflights, access for cleaning and maintenance can be a real problem, as they are often situated high up in the roof and inaccessible. Therefore self-cleaning glazing is an important consideration when looking at the specification of your rooflight.

But what is self cleaning glass and how does it work?

There are actually two types of self cleaning glass: hydrophobic and hydrophilic. Both types clean themselves using water by rolling droplets down the glazing. However, hydrophilic coatings are based on titania and have an additional property that allows them to chemically break down absorbed dirt in the sunlight.

Hydrophilic self cleaning glass

Hydrophilic self cleaning glass is often referred to as having the “lotus effect”, which means it has a very high level of water repellence, much like the leaves of a lotus flower. The titanium dioxide coating on the glass reacts with UV light to generate electrons that break down organic dirt into tiny pieces which rainwater can wash away.

Hydrophilic self cleaning glass panels produce a non-stick surface (much like a frying pan) that water can run off without causing streaking. These types of coatings are resistant to scratches and work on both organic and inorganic dirt. Hydrophilic self cleaning glass reduces the need for manual window washing, keeping your rooflights cleaner for longer.

Photocatalytic self cleaning glass

Photocatalytic self cleaning glass works much the same as hydrophilic self cleaning glass, except that it has an extra coating. This additional coating of titanium dioxide uses the sunlight to break down dirt on the glazing through a process called photo catalytic decomposition. When it rains the water then washes away any build up of dirt.

The coating on the glazing is designed to make any water that hits the glass spread out into an even sheet and easily run off, taking any of the loosened dirt along with it. The even run off of water means that no streaks are left behind and your rooflights dry quickly. The coating on photocatalytic self cleaning glass rooflights is strong and has a long life span.

Stella rooflight and Saint Gobain glass

All Stella rooflights are manufactured using SGG BIOCLEAN self-cleaning glass as standard, offering a highly effective solution. This high performance glazing offers a dual-action ‘hydrophilic’ and ‘photocatalytic’ coating, which as explained above, uses daylight and rain to break down and wash away organic dirt. The special coating works without altering the transparency of the glazing.

The efficiency of SGG BIOCLEAN complies with the European self-cleaning norm for glass EN 1096-5. This standard allows specifiers to differentiate between glass with a classified self-cleaning performance and one without.

How long does self cleaning glass last?

While glass that cleans itself seems like a magic bullet solution, your rooflights will still require some care and maintenance, just less of it. The self cleaning coating on Saint Gobain glass is permanent and the SGG BIOCLEAN® functionality will remain the same over the life of the glazing.

It’s important to note that there are some cases where self-cleaning glass might not deliver the results expected of it. For example, wind-blown spray in coastal areas can cause salt crystals to adhere to the surface. As salt is an inorganic contaminant, it can’t be broken down by the photocatalytic action of all self clean glazing. While this is worth considering, the technology will make the glass cleaner than ordinary glass after a light hosing or rainfall.

In summary, it is important to consider a high specification self cleaning glass for your rooflight as we know from experience that most of our customers are either unable or unwilling to climb up onto the roof to clean them. When it comes to specifying your rooflight and comparing costs, make sure you are making direct comparisons on the type of glazing used, as not all self clean glazing is the same.

The benefits of self cleaning glass

·     A permanent self-cleaning coating that lasts the lifetime of a window

·     Glass stays cleaner for longer

·     Ongoing cost savings with reduced window cleaning bills

·     Clear view outside even when it’s raining, thanks to the sheeting effect

·     Kinder to the environment with a less frequent use of water and detergents

·     Less dirt and grime adheres to the glass so any cleaning is quick and easy

·     Perfect for rooflights as they are often situated in hard-to-reach areas that are difficult to clean.

For more information on Stella rooflights and self clean glazing, give one of our knowledgable team a call on 01794 745445 or email us at

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