Whats the 4 for in Low-E4?
The four in Low-E4 refers to the added benefit of a titanium dioxide coatings. Short story: it makes your windows easier to clean. Long story: Low-E4 has both a coat of Low-E, and another micro-thin layer of titanium dioxide applied. When your windows get wet and the sun shines on them, the titanium dioxide reacts with the light and moisture to break down biological materials such as dirt or insect residue. This makes cleaning your windows easier, as you can wipe the dirt or residue right off instead of having to scrub or even scrape to get your window clean.
