You should evaluate the type of window and cost ( vinyl, wood, fiberglass in order of increasing cost ) . Make sure the manufacturer and company installing have been around for a while, as well as the warranty. The most telling item is the efficiency rating on the products sticker. A quick test is to ask if the windows ( at least till the end of 2010 ) qualify for the federal tax rebate for energyy efficiency.

You may choose to go with low e or low emissivity coating and argon gas between the panes for better efficiency. For aesthetics you may also pay to have contoured decorative grids between the panes for a more natural look.

Most will choose a vinyl window with a U factor of 0.30 or less with 6 over 1 panes with low e coating and argon filled. You cannot go wrong with that for price and performance. www.defrancescoconstruction.com
Links: www.defrancescoconstruction.com