The Home Inspection and Low Emissivity Windows.
The sunlight we feel contains many wavelengths of energy. Two of the wavelengths we are considering are infrared heat energy and ultraviolet light. Low E Coatings on windows are designed to filter out infrared heat energy and ultraviolet light from the sun before they enter our homes through the window panes. The infrared energy wavelength when it enters your home heats objects that come in direct contact with the rays of energy. As a result, this contributes to the heat in our homes and an increased load on our HVAC system in the cooling season. As windows age the Low E Coating, can begin to degrade and become visible. I don’t have final research on this, but I have not found documentation that states the low E coating stops functioning once it becomes visible.