What does the outer layer of a low-e window typically do?

The outer layer of a low-e (low emissivity) window is specifically designed to reflect ultraviolet (UV) light. This feature is essential because it helps to reduce the amount of harmful UV radiation entering a building, which can contribute to fading of furniture, fabrics, and artwork. By reflecting UV light, low-e windows enhance the energy efficiency of the building while also preserving the interior environment.

In contrast, the other options do not accurately describe the primary function of the outer layer of a low-e window. While enhancing structural integrity is an important characteristic of window design, it is not the specific role of the low-e coating. Similarly, increasing thermal mass pertains to the material's ability to retain heat, which is unrelated to the functions of low-e windows. Finally, while low-e windows can decrease the amount of infrared light and heat transfer, their primary purpose is not to reduce visible light transmission but to maintain thermal efficiency and protect against UV rays.