The casement was a window that opened like a door. Hinged on one side. Swung outward. The casement did not slide up like the double-hung. The casement swung open and the whole window was the opening. One hundred percent of the casement was ventilation. The double-hung gave you fifty percent. The casement gave you everything. The casement was the generous window. The casement held nothing back.

The casement had a crank. A small metal handle at the bottom of the frame that the hand turned clockwise to push the window open. The crank was a worm gear. The worm gear converted the turning motion of the hand into the pushing motion of the arm that pushed the sash and the sash swung on the hinge and the window opened one degree per turn. The crank was slow. The slowness was the control. You opened the casement exactly as far as you wanted and not one inch farther. The double-hung slammed open. The casement persuaded.

The casement caught the wind. The open casement was a sail mounted on the side of the building. The wind hit the glass and the glass deflected the breeze into the room. The double-hung opened a slot. The casement opened a scoop. The breeze through a casement was not the same as the breeze through a double-hung. The casement breeze had direction. The casement breeze had been aimed. The person who cranked the window chose the angle and the angle chose the breeze and the breeze cooled the room the way the person wanted. Air conditioning before electricity. The hand was the thermostat.

The casement leaked. The seal between the sash and the frame depended on compression. The crank pulled the sash tight against the weatherstrip and the weatherstrip sealed the gap and the gap was sealed until the weatherstrip wore out. The weatherstrip always wore out. The double-hung had sash weights on ropes and the weight held the window where you put it. The casement had the crank and the crank held the window where you turned it. The weight was gravity. The crank was mechanics. Gravity does not need maintenance. Mechanics do.

Nobody installs casements in apartment buildings. The casement swings outward and the outward swing endangers the person on the fire escape and the person on the sidewalk and the window washer on the scaffold. The casement is a suburban window. The casement needs room to open. The city does not have room. The city has the double-hung because the double-hung opens inward into its own frame and takes nothing from the street. The casement asks the world to make room. The double-hung asks nothing. In the city the window that asks nothing is the window that survives.

See also: Sill, Mullion