Hi ZIns, Oberon offered professional technical details so I will chime in with homeowner experience. Yes, even with Low-E, there will be fading. Depending on the amount and intensity of exposure and the finish, it is a matter of how much and how soon. In a situation where the sun is very mild and light, by the time fading is noticeable, it may also be time to refinish the floor. My guess is the floor is not receiving year-round exposure, true? The sun is stronger and deeper during some time of the year and weaker and less intense at other times, is that so? We have seasonal sun intensity problem too and solve it with a combination of solution. We use rugs to protect several sections of our floor during mid-Spring through late Summer. The rugs are removed to prevent tripping when we have visitors. The rugs are also removed around Autumn when the sun is low and the exposure is much less intense and shortening each day. We have old furniture in one area by our French doors and my wife made knitted coverings to cover the furniture. As necessary, we remove the covering when appropriate. Outside the French doors, we installed retractable awning so that during extremely hot summer days, the awning extends to provide cover without blocking natural light. Our goal is to not use any window treatment because we enjoy natural light and the views. Hope this helps a bit.

Depending on where the home is, the lower in the horizon passive solar may be of some benefit. SHGC is what you focus on in the summer and U-Factor is more appropriate measure for the wintertime savings. Where is the home located? What are the SHGCs on the comparable units and this wouldn't be the first time a salesperson was incorrect. I know that last part is shocking....

My LoE 272 windows replaced Pellas that had no UV coating (as an aside, don't get Pellas, avoid). I have not replaced all my windows (too expensive), but am replacing them a few at a time. So I can compare them since I currently have both. I have several very large windows that let in a lot of light, and there is no problem with that. I do not see that the glass is darker. I definitely notice less burning and sun bleaching my furniture and no longer overheating my south-facing rooms. I will say that my house plants that need a lot of sun have not flowered or grown, even though I was assured the LoE 272 would not affect them. My plants that need less sun like my African Violets are doing well. You should really speak with your contractor too since it sounds like he has proposed LoE 366. My contractor told me our climate doesn't need that though he would have ordered them if I asked.

@msgal39564 - what did you decide on the glass and how did it work out? Natural sunlight is very important to use with a housebound family member (who does notice the glass difference in newer homes), so we are really weighing our options in a similar climate.