Roof windows are operable windows that are incorporated at part of the design of a roof. Often confused with skylights and sky windows, the roof window does differ from each of these other architectural and natural lighting elements in a few basic ways. A roof window is often a good option when there is a desire to allow both light and fresh air into the space.

While many people assume that the roof window is just another name for a skylight of sky window, that is not the case. All three of these design elements are glazed openings that are added to the roof in order to make more efficient use of natural sunlight. However, there are a couple of distinctive traits that set the roof window apart from the other two options.

A roof window tends to be larger than a skylight, making it possible to enjoy a wider view of the sky overhead. In addition, skylights are usually stationary; that is, they cannot be opened and closed. With some designs of a roof window, it is possible to retract a portion of the glazed panes to allow in fresh air as well as enjoy the natural light.

A roof window is also different from a tubular skylight, in that the light is not directed through any type of channel or tube in order to provide lighting for the interior of a building. This type of light tube design is often employed with buildings where the installation of a skylight or roof window is not practical.

When comparing a sky window to a roof window, the main difference has to do with the type of roof involved. When the glazed panes are fitted into a flat roof, the construction is normally referred to as a sky window. However, a true roof window requires that the roof have a least a modest amount of slope.

One characteristic that sets the roof window apart from both the skylight and the sky window is the fact that a roof window offers a means of escape from the building in the event of a fire or other threatening situation. This is not true of the other two options, which are normally set in place and cannot be opened and closed at will.

While a roof window is normally included in the original construction of the building, it is possible to add the design feature to an existing structure. As long as the framework and the slope of the roof allow for the inclusion of this type of window, it can be installed with relative ease. Many manufacturers offer prefabricated window inserts of this type that can be installed by a professional in a matter of hours.