[herr_oberst]

Pella. From Lowes. I did the exact same thing that you're doing. My 1973 ranch house with aluminum windows was cold and drafty. I replaced the large front window and the sliding patio door three years ago, and have been replacing the rest of the windows one or two at a time.

I'm not sure if the furnace runs any less, but it is definitely quieter, and the drafts are gone. (Plus, the casements on either side open oh, so smoothly!)

(The front window needed to be custom made to size, but I'm finding that all the rest of the windows are standard size - meaning, cheaper!)