What it is: Similar to a casement but hinged at the top.
Pro: When extended, the glass slopes downward, so the window can be left open when it rains. It can be used as a clerestory (a window near the top of a wall) to let hot air escape.
Con: Offers only partial ventilation and is usually too small to use in the event of an evacuation.
Cost: About $100 to $1,100.
Tip: Check labels for a window’s U-value (aim for 0.35 or lower). The lower the number, the better its insulating property.