The material you choose for your window’s frames will determine, to a large extent, how your windows work. The only thing that has as big an effect is the glass itself. Though both will work together to determine your window’s qualities, the material of the frame forms the basis of much of the window’s performance and functionality, as well as the level of upkeep the windows will require.
Wood has been in use as a window material for so long that it is the basis for comparing whether a particular window is good or not; most windows will be rated as being better or worse based on how they compare to wood. Wood is a great insulator, and limits the amount of heat transfer between the outside environment and your home’s interior. It is, however, subject to expanding or contracting based on the weather, and without regular maintenance will quickly lose in terms of performance.
Vinyl is proof against damage from ultraviolet light, is resistant to moisture, and does not require the maintenance that wood does. Insulated vinyl frames have hollow cavities where extra insulation can be added, making it a better insulator than wood or standard vinyl.
Aluminum is strong, light, and does not require regular maintenance. However, it readily conducts heat and, without thermal breaks, provides little in the way of insulation.
Fiberglass is known to be dimensionally stable, with better thermal performance than wood or uninsulated vinyl. Like insulated vinyl, the insulating ability of fiberglass can be enhanced by adding extra insulation in the cavities within the frame.
Composite materials, such as Renewal by Andersen’s Fibrex, tend to be highly stable, with structural and thermal qualities that exceed that of wood, while at the same time standing up better to the effects of moisture and decay.
The glass options you choose for your window have as big an effect as the frame material, as we see in part II.