Casement windows, which open sideways with a hand crank, offer a few advantages over other types of windows, especially slider windows and double-hung windows. Slider windows have a movable sash that slides sideways, opening and closing with a clack. When sliders' tracks get gritty, they can be hard to open and close. Double-hung windows, which have a sash that moves up and down, can be hard to open because you're fighting gravity. But casement windows quietly crank open like a door, and there are no problems with gravity because the sash is hinged for sideways movement.
If you need a window that prevents air infiltration, the most weathertight window you can purchase is a fixed window. But the second most weathertight window is a casement window. This is because the casement's window seal meets the casement sash straight on. Ironically, casement windows will give you more air movement when you want it. The opened sash can act as a kind of chute to help force more breeze into your house. Finally, inside screens are easier to clean. If the window is on the second story or higher, you will appreciate being able to pull out the screen from the inside.
While casement windows do have their fans, a few aspects of their design put off many homeowners. Before jumping into an expensive casement window purchase, carefully consider these downsides:
Casements Have More Mechanical Parts to Break
Most casement windows have a crank or other type of mechanical device to help open and close the sash. Casement windows will often have problems develop with this crank: handles break, gears freeze up, become rusted, or break. While a double-hung window may not always be the easiest to open, it is a very simple operation with a lifting assist device that can inexpensively be replaced. Slider windows, consisting of little more than a moving sash and a latch, have even fewer mechanical parts that can potentially break.
Side-By-Side Casements May Conflict With Each Other
Two casement windows installed next to each other in a straight line will conflict if the swing is reversed. For example, if one window opens to the left and on that left side is another window opening right, the open sashes will conflict. While this conflict should be an anomaly (and homeowners do need to be aware of this during installation), there is a second, related problem that can happen. When two casement windows are installed in an inside corner, sashes might conflict regardless of the direction of the swing.
Casement Windows Do Not Allow Most Window A/C Units
If you have conventional air conditioner window units, they will not fit in casement windows. Window A/C units fit best in double-hung windows because the sliding sash can close down to seal off the top of the window unit. But casement sashes cannot do this. Not only that, casement window sashes do not open far enough to allow you to install the window unit. Barred from installing conventional, low-cost window unit A/Cs, you will spend about several times more for a casement/slider A/C unit.
Open Casements Are More Exposed to the Elements
Because casements open outward, the edges are exposed to sun, rain, snow, and other elements. The top edge of a casement window particularly is exposed and gets weatherbeaten fast. One way to combat the harshest elements is to make sure that you quickly close the sash when it rains or snows. But even mild weather will slowly deteriorate the seals and the frame of the window.
Casement Screens Are on the Inside of the House
Because casement windows' sashes open outward, its insect screens must be on the inside. This arrangement does make sense. Otherwise, you would have to access the windows with an extension ladder merely to remove and replace the screens. But the downside is that children can access and tamper with these types of screens.
Open Casement Sashes Can Break
Wind can catch the leading edge of casements and, with a sail-like effect, break them off entirely or damage them. This is not a highly unusual event, either, as it doesn't take much wind to catch the sashes. Casements' hinges tend to be the main victims of wind gusts.
Sun Reflection Can Be a Problem
Because of the angle of the opened sash, it can occasionally reflect sun directly into the house. Sometimes this can be a welcome relief for a gloomy room. Other times, it can have a piercing effect much like the reflection of car windows in a parking lot. If you live in a highly sunny place and want to avoid the sun as much as possible, casements may not work for you.