Windows are to a room as a pearl necklace is to the throat of a woman. They both set off the other. Windows come in many sizes, shapes and kinds. They also provide four vital functions: let in light and air (ventilation), provide protection and visual beauty. What kind is provided in a room depends on many factors. Some of the most common types are described below.
Bay Windows: A kind of architectural enhancements to a room - these windows project out beyond the exterior wall to create an illusion of a larger interior. The conventional ones are three sided with the two side windows returning to the wall at an angle. They let in a lot of natural light and sometimes allow a fantastic view of the outside.
Because of the nature of a bay window, window treatments require special care. If they look out into a secluded area(they usually do not), then the nature of treatment required is fairly simple and has only to complement the style and décor of the interior of the room. But if it looks out into the public, then the treatment has to be more thoughtful. Some ideas for the treatment of bay windows include bay window curtains, valances, window shades and window blinds. The treatment has to be both functional and aesthetic as it is open to public view.
The use of the space created by the bay window also requires some imagination. Since there is ample light, one idea would be to keep some indoor plant for effect. Some seating arrangement, the seats in conformity to the style of the other furniture in the room is another option. So is the addition of accessories like a large vase on one side of the window or two smaller ones on both side of the window will enhance the beauty of the room and the window.
There are two variations of the conventional bay window, the "box" and the "circle" bay windows. As the names imply, the box bay window is shaped like a box, the side windows being perpendicular to the exterior walls and the circle bay is semi-circular in shape. The box bay creates more space than the other two.
Oriel Windows: These are similar to bay windows in that they project from the walls but are polygonal in shape and do not extend to the ground and are therefore found in the upper stories of a building. They originated as a variation of a porch and are commonly found in buildings built in the Gothic Revival style or the Queen Anne style of architecture. They are now becoming common in modern design. Compared to the more common bay windows of the conventional, the box and the circular type they allow more light and more significantly better ventilation due to the larger surface exposed to the exterior.
Usually supported by "corbels", a weight bearing stone piece that is ornamentally carved in stone houses, they can also be supported by metal or wooden brackets. Considering that oriels appear in homes with an elaborate style, these supporting brackets can also be quite ornamental. This type of window is also popular in the Middle East where they are known as "mashrabiyas" and are usually for the convenience of women folk who can look out from these windows without being seen and gives them a sense of freedom. They can also be seen in India.
Casement Windows: These were the most common type of windows that were in use before the introduction of the sash windows. Casement windows open like doors, swinging either in or out like a door. Unlike a door, the casement window is opened by the use of a crank (or some variation) and not by a knob or a handle. The casement window either pivots to the right or to the left. One of the disadvantages of a casement window is that there is the possibility of children falling out while looking out. Another disadvantage is that they are more exposed to the elements - rain, sunshine, snow, sleet and more depending on the place where you live and are likely to get weathered faster.
A variation of the casement window that either pivots(swings) to the left or to the right is the one that swings upwards, i.e., top-hung. They are called "awning windows" and are usually rectangular, wider than longer.
Paired Windows: These are two windows placed next to each other with a support between them called a "mullion" which is nothing but a vertical frame that provides a separation between the two glass panes. Usually paired windows come under an arch or will have arched tops. They look better in large rooms since they themselves are relatively larger.
Palladian Windows: Named after the Italian Architect Andrea Palladio, a palladian window is made up of three windows with an arch over the center window which is also usually larger than the other two. It is also known as the Serlian or the Venetian Window.
Ribbon Windows: These are nothing but a row of windows separated by vertical posts called "mullions". They are an extension of the paired widow and are used usually in places where added lighting and ventilation is required and are usually found up high on a wall. Such windows, if installed very near the ceiling are called "clerestory" windows. They bring day light deep into the interior of the house and add to the feeling of roominess. They also are a source of solar heating and keep the room warm even in the long winter days.
These are some of the more common types of windows. Other types include the jalousie(louvered), the hopper (opposite to the awning), the cathedral, the French etc. What kind of window you use depends on your individual taste.