Does anyone have any experince with Crestline fiberglas windows? WWW.crestlinewindows.com They have a tripple pane casement with a U.19 rating which is good for a US company.

Sorry, but the crestline web site does not have the fiberglass windows on it. I found the windows at Menards and have the brochure with details.

That is a good U rating . . . but unless Crestline has improved the overall quality (workmanship and materials) of their windows recently, I wouldn't recommend them. In my 40 years of experience Crestline has always been known as one of the cheaper brands, and one that doesn't hold up well over time. If you want a good quality triple glazed (with glass, not plastic film) window, Loewen and Marvin are the only manufacturers I would trust at the moment. Yes, they'll cost a lot more than Crestline windows. But you won't be replacing windows for the second time 10 or 15 years from now. If you want good quality cheap windows, Pella ProLine makes some very good casement and awning windows that are very reasonably priced (I'm less impressed with their double hungs), and also available from Menard's, but they're not triple glazed. In general, I'd beware of any triple glazed windows with plastic film from manufacturers making fantastic claims. Once the plastic film technology is proven to be reliable over a long period of time, the old reliable window manufacturers like Pella, Marvin, Loewen, and a few others, will be using it too.