When most people choose windows, they begin by considering the frame material.

The material used to manufacture the frame governs the physical characteristics of the replacment window, such as frame thickness, weight, and durability, but it also has a major impact on the thermal characteristics of the window.


The window U-factor, as given on the NFRC certified rating or label, incorporates the thermal properties of the frame, as well as the glazing.
Since the sash and frame represent from 10 to 30 percent of the total area of the window unit, the frame properties will definitely influence the total window performance.

Vinyl Windows

Plastics are relative newcomers as window frame materials in North America. Vinyl, also known as polyvinyl chloride (PVC), is a very versatile plastic with good insulating value. Vinyl window frames do not require painting and have good moisture resistance, multiple chambers in the frames add rigidity. Because the color goes all the way through, there is no finish coat that can be damaged or deteriorate over time -- the surface is therefore maintenance-free. Some vinyl window manufacturers are now offering surface treatments like laminates (wood veneer, paintable/stainable, maintenance free) and coatings. These products increase color selection and surface appearance options. Recent advances have improved dimensional stability and resistance to degradation from sunlight and temperature extremes.

In terms of thermal performance, vinyl frames are comparable with wood, while there are minor differences, depending on the frame construction. Small hollow chambers within the frame reduces convection exchange, as does adding an insulating material.

Wood Windows

The only choice for some traditionalists, wood offers a pick of colors (it can  be changed later on).Wood frames have good insulating value and structural strength, but require periodic cleaning and painting. Well-built and well-maintained wood windows can have a very long life. Paint protects the exterior surface and allows an easy change in color schemes.

Wood Clad Windows

A variation of the wood-framed window is to clad the exterior face of the frame with either vinyl or aluminum, creating a permanent weather-resistant surface. Clad frames thus have lower maintenance requirements, while retaining the attractive wood finish on the interior. While vinyl and enameled metal claddings offer much longer protection to wood frames, they are generally available in a limited number of colors.

Composite Windows

Most people are familiar with composite wood products, such as particle board and laminated strand lumber, in which wood particles and resins are compressed to form a strong composite material. The wood window industry has now taken this a step further by creating a new generation of wood/polymer composites that are extruded into a series of lineal shapes for window frame and sash members. These composites are very stable, and have the same or better structural and thermal properties as conventional wood, with better moisture resistance and more decay resistance. They can be textured and stained or painted much like wood. They were initially used in critical elements, such as window sills and thresholds in sliding patio doors, but are now being used for entire window units. This approach has the added environmental advantage of reusing a volume of sawdust and wood scrap that would otherwise be discarded.