Casement windows are perhaps most recognizable to the homeowner as the windows that operate by turning some sort of crank mechanism, which in turn opens the window. Most other window types do not utilize such a mechanism so this is a good way to distinguish a casement type window.

Basically, a casement window unit is comprised of one or more separate sashes that are hinged. These hinges allow each operating sash to pivot and open, much like the way a door operates.

Casement windows offer some distinct advantages. To start, they are usually the most energy-efficient type of operating windows available. Only fixed windows are more draft-resistant than casement windows. The draft-resistance advantage of casement windows is due to the way in which the casement windows’ sash (the frame that surrounds the glass) closes against the frame of the window, creating a more positive seal than other window types that operate by sliding against or between their frames. Wind loads blowing against a casement window actually press the casement window against its frame, so the harder the wind blows, the tighter the seal!

Casement windows are also good candidates for bedroom windows, as their design, which allows the entire sash to pivot aside, provides a large opening as an escape route in a fire situation.

There are also some disadvantages associated with casement windows. They can be more difficult to clean on the outside when compared to other mounting designs -some manufacturers offer different types of ‘quick-release’ hardware to overcome this limitation, but this should be determined in advance. Additionally, some people just seem to dislike having to operate a crank to open a window!

There are certain restrictions on the sizes of the individual sashes of casement windows, and these can vary from manufacturer to manufacturer. These restrictions are caused by the way the window sash hangs from one side, limiting how wide each sash can be. If casement window sashes get too wide, there is a danger their weight could cause sagging of the sash over time, especially if the window is left open frequently. When larger glass areas are required than can be provided by a single-sash casement window, units are built up from two or more sashes, joined by dividing mullions. Often one of the sashes will operate while the adjacent sash is fixed on double units, but most window manufacturers will offer different configurations, depending on the requirements of the application.

There is little maintenance required of most casement windows. Simply lubricating the operating hardware once a year or so and maintaining the exterior finish is usually all there is to it. Casement windows are a time-tested and proven design, and could be the right choice for many window replacement projects.