If you can reuse your old windows in any construction and renovation project, then you should. While recycling windows and other glass products might seem like a good thing, builders rarely do it. Why is that? First, glass is cheap to make. There's a seemingly unending supply of its main ingredient: sand. Second, glass makers have very precise requirements for their products, and recycled glass sometimes doesn't fit well within the specifications of these products. While all glass is basically the same thing, there are subtle differences depending on what the glass is used for.
Additionally, window glass includes many parts, such as aluminum, vinyl, insulating spacers and lamination layers that need to be removed before the window can be recycled. It is usually very time consuming and costly to remove these parts [source: American Architectural Manufacturers Association].