Head: Main horizontal frame member at the top of a window or door.

Head Expander: u-shaped extrusion slipped over the frame head that, when pushed up, closes the gap above the window after a window is installed.

Header: horizontal framing member placed over the rough opening of a window to prevent the weight of wall or roof from resting on the window frame.

Heat gain: The transfer of heat from outside to inside by means of conduction, convection and radiation through all surfaces of a house.

Heat loss: The transfer of heat from inside to outside by means of conduction, convection, and radiation through all surfaces of a house.

Hinge: A movable joint enabling a window to swing open.

Hopper: A window unit in which the top of the sash swings inward.

Horizontal Slider: A window with a movable sash that slides horizontally.