Inoperable: no longer opening, closing, locking, or unlocking as originally designed.

Insulating glass unit:  two or more lites of glass spaced apart and hermetically sealed to form a single unit with an air- or gas-filled space between each lite.

In swing French Door: A French door with panels that swing to the inside. One, two, three and four panel units available as stationary or operating.

Insert window: A new window unit intended to be installed inside the frame pocket of an existing window.

Insect screen: A tightly woven mesh attached to a frame; allows outside air ventilation while keeping insects out.