Self cleaning glass: how it works

Self cleaning glass has an invisible coating that breaks down dirt in daylight and lets rain wash it away, so the windows need cleaning less often. It does not remove the need to clean altogether. This page is based on Pilkington’s page for Activ Clear, one of the best known self cleaning glasses in the UK, so what it says applies to that product.

How self cleaning glass works

Pilkington describes Activ Clear as UK-manufactured, on-line coated glass intended to give householders low-maintenance clean windows. The coating works in two stages:

1. Daylight breaks the dirt down. The coating reacts with natural daylight to break down and loosen organic dirt. This is the photo-catalytic stage.
2. Rain washes it off. Water is attracted to the coating and spreads evenly across the glass instead of forming droplets. That helps to wash away dirt and reduces streaking. This is the hydrophilic stage.

Pilkington says the glass keeps working on cloudy days and at night, so it does not need direct sun. The coating is a hard, pyrolytic one that it says lasts the lifetime of the glass.

What self cleaning glass does not do

Self cleaning glass is not maintenance-free. In long dry spells the rain stage cannot happen, and Pilkington’s own advice is to hose the glass down with clean water. The page does not claim that the coating removes every kind of dirt, so heavy marks such as paint or sealant will need ordinary cleaning. It also does not say how well the coating works on sheltered panes that rain never reaches, such as those under a deep porch, so do not expect the same result there.

Where it is worth having

Pilkington’s list of uses includes replacement windows, roof lights, extensions, conservatories and hard-to-reach places that are difficult to clean. That last group is the strongest case. If a window needs a ladder or a long pole, glass that needs washing less often saves real effort. For ground floor windows that you can reach with a cloth, the saving is smaller and you may prefer to spend the money elsewhere.

Looking after it

Ask the fitter or the maker for the cleaning guidelines for the glass you are buying, and follow them. Take care with anything that scratches the glass, because a damaged coating cannot do its job. Our page on scratches on glass explains what repair can and cannot do.

What to ask in a quote

• Which self cleaning glass is it, and in which panes?
• Is it on every window or only some?
• What does it cost per window, compared with ordinary glass?

The price difference is for you to weigh against the effort saved, and the quote checker will show you whether it is listed. Read about the other glass options for replacement windows, then get free quotes.