What Is a Clad Wood Window?

Window Construction

• The complex framing of wooden windows developed during times when manufacturing a large pane of glass involved expensive problems. Using many small panes instead made glass windows more practical but required complicated wooden frames both to hold the panes in place and to hold back the cold wind. Outside, the wood framing weathered quickly, so wooden windows needed frequent painting. Window putty sealed drafty gaps between the frame and the panes. Both paint and putty needed to be reworked regularly. Modern windows with better and cheaper glass require less framing, and cladding the exterior with plastic or metal eliminates most of the tedious expensive maintenance.

Cladding

• Many homeowners still prefer the look of wood-framed multi-pane construction. Modern window designs can keep the traditional look and still improve the energy efficiency by including doubled panes of either glass or acrylic. The sealed space of dead air between the panes reduces heat loss. Wood still provides the basic structure for this more complex window style, but other materials armor and support the exposed wood. Some cladding methods increase structural strength by replacing parts of the wood framing with stronger synthetics. Cladding reduces weathering and simplifies upkeep by replacing the paint and putty of old designs.

Types

• Window manufacturers use three types of materials to clad wood-frame windows. Vinyl-clad windows can mimic a natural painted wood surface. Pressed vinyl materials can even show the ridges and patterns of wood grain. Vinyl-clad wood windows cost less than windows clad with aluminum or fiberglass. Vinyl contributes less structural strength but works well as a semi-permanent coating for the wood frame. Aluminum cladding increases window strength and lasts longer than vinyl cladding. Anodized aluminum cladding resembles a painted surface and resists abrasion as well as weathering. Fiberglass, the most expensive cladding, offers the best insulation value, excellent structural support and a long product lifetime.

Problems

• Vinyl cladding softens on hot days and loses structural strength while becoming less flexible as temperatures fall. Vinyl cladding fades in sunshine as ultraviolet light bleaches its surface and becomes brittle as it ages. Noticeable problems develop after five to 10 years, according to the Minnesota Green Affordable Housing Guide. Vinyl windows lose value faster than well-maintained wood frame windows or other types of clad wood windows. Aluminum retains its original strength but provides little insulation. Moisture can condense behind cold aluminum cladding and cause rot and mildew on wooden frames. More expensive fiberglass-clad wood windows rate the best overall.