Before class on Tuesday I was unaware that such things existed, that windows can clean themselves now. Once I found out about this, I wanted to find out even more. Developed in 2001, Pilkington Activ, became the first company to develop the self-cleaning windows, in fact, glazing is perhaps the largest commercial application of self-cleaning coatings to date. It is made up of a thin layer of titanium dioxide, this layer acts to clean the window in two different stages: photocatalysis and hydrophilicity.
When reacting with UV light, the photocatalysis breaks down organic dirt absorbed into the window, and when the glass is wet, or when it is raining, the hydrophilicity causes the water to spread out evenly on the surface, rather than water droplets, and it reduces streaks. The thin layer than washes the dirt away. Titanium dioxide has become the material choice of use, not only for self-cleaning windows, but for self-cleaning surfaces in general. It is also non-toxic and inexpensive, which increases the demand for titanium dioxide.
The dome of the Robson Square ice rink in Vancouver, newly renovated is covered in 9,000 square feet of self-cleaning glass combined with low emittance (low-E) glass. The low emittance glass reduces the U-factor by suppressing radiative heat flow. The Museum of Earth in Ithaca, NY uses the same combination of self-cleaning glass and low-E glass, which cuts down on maintenance and operating costs.