At first glance, a window looks like a pretty simple piece of equipment. It has a frame, glass, and 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 many 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 right, has movable upper and lower sashes that slide in tracks in the side jambs. A variety of specially milled pieces go in to making up the jambs, frame, casing, and sashes.
Window frames and sashes are constructed from wood, aluminum, vinyl, or a combination of these materials. Of these, wood is the best insulator and tends to yield the nicest appearance from both indoors and out. Vinyl and aluminum are more durable and maintenance-free so 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 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 the section on Window Glazing.)
A nail-on metal window, shown at left, has many of the same parts and pieces as a wood window, except that 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.
