I had the Marvin ‘Infinity’ windows installed. They cost a bit more and the turn around time was a bit longer but well worth it. For the first time my bedrooms were comfortable in the winter and my heating bill was about a third less then this time last year. Installation was quick and clean. I went with the fiberglass frame over the vinyl because it just seemed like a better window. I am an architect so I know a good window when I see it.