More and more window manufacturers are offering fiberglass windows
Best Manufacturers
Fiberglass windows are not as common as other types of windows today, although more and more window manufacturers are considering producing this new type of window. Here is a brief list of some of the top companies that currently offer fiberglass windows:
Milgard
Milgard was one of the first major window manufacturers to begin production of fiberglass windows. It currently offers the Ultra Series of fiberglass windows of the following types: single/double hung, horizontal sliders, picture windows, radius, casement, awning, bay and bow windows.
Fibertec
This company specializes in fiberglass windows and offers standard fiberglass frames as well as wood-clad. Their available types are casement, awning, double-hung, bow/bay window, sliding windows, and many customizable shapes.
Fiberframe Windows
Offer a number of fiberglass options, focusing on energy efficiency and physical strength. See site for details on available windows.
Pella
Pella offers a line of windows made with Duracast® - a fiberglass composite that is 9 times stronger than vinyl and twice as strong as aluminum. Pella Impervia® replacement windows come in single/double hung, fixed frame, sliders and special shapes.
Marvin
Marvin offers a line of replacement windows called Integrity that provides high performance and low maintenance. These fiberglass windows come in single/double hung, glider, and polygon.