These are impact windows where the impact glass has a clear, completely unnoticeable, low emissivity coating (low E coating) applied to them. The coating blocks certain wavelengths of light from passing through the pane while still allowing the passage of visible light. In other words, the coatings reflects (blocks) UV light away from the window. This helps reduce UV and thermal energy (heat) from entering your home through your windows. This keeps your home cooler while still allowing natural light in. This coating is an option available on impact windows. Learn all about low-E glass with these helpful resources: 1. Complete guide on Low E Impact Windows for Florida Homeowners 2. Guide on What is Low E Glass And How it Works