For those who value energy efficiency and longevity in their windows, fiberglass is by far one of the best window material choices. It is weather- and dent-resistant, very easy to clean, and can keep your energy bills noticeably low for a long period of time. As far as maintenance is concerned, you’ll never have to refinish fiberglass window frames. Fiberglass windows also require little to no natural resources to produce, making them one of the more eco-friendly options commercially available.