In the 1980′s, more restrictive energy codes were enacted which led to new innovations.
Extruded vinyl windows were developed to address the problems with the older windows. Extruded vinyl resists heat loss, can't rot, and needs next to no maintenance. Over the next thirty years, demand for energy efficient windows drove the industry to create better and more efficient glass systems. The latest highly efficient glass and vinyl windows can provide U values around 0.20, 5 times better than the old single glazed wood and aluminum windows.
Wood windows with exterior cladding have also been developed. The cladding to the exterior can be aluminum, vinyl, or fiberglass; and serves to protect the interior wood from weather damage. These windows have similar energy saving characteristics to vinyl windows, while still providing the beauty of wood.
The most recent addition to window design is the fiberglass window. Fiberglass is very strong and weather resistant, and has the added advantage of being paintable both inside and out. Fiberglass has similar insulation characteristics to vinyl.