Contemporary windows are available in a number of innovative styles. You can buy a bent-glass corner window, curved-glass windows, or casements with no center stile, for example. Some beautiful bow and bay windows, made up by combining fixed and operable units, are also common.

Double-hung windows, classic in appearance, offer excellent control of ventilation. They have an upper outside sash that slides down and a lower inside sash that slides up. Hidden springs, weights, or friction devices help lift, lower, and position the sash. With certain types, the sash can be removed, rotated, or tilted for cleaning. If only one sash slides, the window is called “vertical sliding” or “single-hung.”

Casement windows, hung singly or in pairs, are side-mounted on hinges and operated by cranks that swing the sash inward or, more commonly, outward. They open fully for easy cleaning and offer excellent ventilation because they can “scoop-in” breezes.

Horizontal slider windows may have one or more fixed panels in addition to one or more panels that slide in horizontal tracks. Only half of the total window may be opened for ventilation at a time.

Awning windows are lik horizontal, top-hinged casements—they tilt out at the bottom, offering partial ventilation, an unobstructed view, and reasonably good security.

Jalousie windows, also called louvers, are made of glass slats set in metal clips that can be opened and closed in unison. These offer good ventilation but are drafty in cold climates.

Hopper windows are like awning windows except they hinge at the bottom. Hoppers are normally used for ventilation above a door or window, where they are protected by eaves.

Tilt-turn windows offer distinctive European styling and have a special advantage over conventional double-hung windows: They tilt in toward the room at the top and also turn a full 180 degrees for easy cleaning. This feature also makes them excellent emergency exits. Look for a multipoint locking system; this adds security and helps keep the window tightly closed.

Round-top windows and others that are geometrically shaped are used as architectural accents.

Bow windows project out like bays but have more than three sections that join to form a gentle curve. Center windows are generally fixed; side sashes are typically casement windows.

Seamless bent-glass corner windows are a fairly new product that offers unobstructed views at the corner of a house.

Bay windows project out from the wall; a center window parallel to the wall is flanked by two windows attached at an angle, usually casement or double-hung styles. Box bays have side windows at a 90-degree angle.

Glass block is a light-allowing alternative to conventional windows, used both in exterior and interior walls. Various patterns allow varying degrees of view or privacy. Typical sizes are 6-, 8-, and 12-inch squares and 4-by-8 and 6-by-8 rectangles made for 4-inch-thick walls.