I live in western MA, where the local window contractors seem unanimously to agree in their recommendation of windows by National Vinyl Products, a MA-based company that does business primarily in New England. I'm a little concerned not to see any mention of them in discussions here. While it's doubtless true that quality installation is the key, I'd still hope to be installing a quality product. I like the idea of working with local contractors and local manufacturers; the ratings seem good; the company itself was responsive to my further questions as I was gathering rating info. The window in question is named Northwind III; the argon-filled has a U-factor of .31, VT .50, SHGC .36.
Does anyone here have more than glancing experience with National Vinyl?
None of the folks I consulted mentioned Schuco as an option, though I see those are popular on this board.
The other window I'm considering at this point is the Gorell 5300, which comes to me at about 33% higher cost than the Northwind.