Replacement windows with frames manufactured of fiberglass are
not as common as those made of vinyl or wood, however they are
gaining in popularity. As a newer type of window, it is often more
expensive than its more common counterparts, but fiberglass also
offers superb energy efficiency and is much stronger than either
vinyl or aluminum. Fiberglass windows are low maintenance, are
resistant to glass seal failure as well as rotting, splitting,
warping and corroding. They do not succumb to temperature swings,
moisture or structural damage. Manufacturers of fiberglass
replacement windows include Pella, Marvin, Milgard, Fibertec and
Fiberframe.