Window Film Basics: What It Is and How It Works

https://fast-wiki.win/index.php/Low-E_Coatings_and_Window_Film:_What_You_Need_to_Know

Window film sits on the inside of glass, a thin laminate that changes how a window behaves without altering the frame or structure. It is a simple concept with a surprising range of implications for comfort, energy use, and daytime privacy