WHAT THEY ARE: Imagine a double- or singlehung window turned on its side, and that’s pretty much what a horizontal slider is. As the name suggests, these doors slide open horizontally rather than vertically.
PROS: Sliders create a good seal for energyefficiency. They’re also easier to open than double- or single-hung windows.
CONS: Not available in as many sizes or materials as double- or single-hung windows. Plus, only half the window can be opened at one time, so they don’t allow in as much breeze as casement windows.