At first glance, a window looks like a pretty simple piece of equipment. It has a frame, glass, some basic hardware. But if you look a little closer, you'll find there’s much more than first meets the eye.
A window must be designed to allow in light and views—and, in some cases, ventilation—yet seal out the weather. It must shed heavy rain without leaking and block powerful winds. And, if it’s operable, it must open and close easily. To handle these tasks effectively, it has many parts and a surprisingly complex construction.
A double-hung wood window, shown below, has movable upper and lower sashes that slide in tracks in the side jambs. A variety of specially milled pieces make up the jambs, frame, casing, and sashes.
Window frames and sashes are built from wood, aluminum, vinyl, or a combination of these materials. Of these, wood is the best insulator and tends to yield the nicest look both indoors and out. Vinyl and aluminum are more durable and maintenance-free; some manufacturers apply a cladding of these materials to wood windows. Some windows have real divided lites held in place by muntins; others have snap-in wood grilles that imitate the look of divided lites. Though snap-in grilles don’t look as substantial as real muntins, windows with these are less expensive and easier to clean than real divided-lite windows because they’re actually a single sheet of glass.
The type of glass in a window has a great deal to do with how the window performs. For more on this see our section on Window Glazing.
A nail-on metal window, shown below, has many of the same parts and pieces as a wood window, only some of them are formed as single parts. The flange around the perimeter is made to nail on to the exterior wall sheathing for easy mounting during construction.
