Discussion Board Forum for Vinyl Windows

Is there any formula to calculate how much energy savings you can expect from installing vinyl replacement windows based on certain factors, such as, # of windows replaced vs. total # of windows in the house, or floor by floor, or r value of new vs. old or anything like that?

I live in the San Francisco Bay Area and have single pane aluminum windows and I'm looking to replace them with a vinyl retrofit. All installers offer lifetime warranty and so do most window manufactures. So, why choose one over the other? I'm looking for quality of the product. Sight lines, 'the l...